Problems3 MOLE CONCEPT PROBLEM 1 A crystalline hydrated salt on being rendered anhydrous, loses 45.6% of its weight. The percentage composition of anhydrous salt is: Al = 10.5%, K = 15.1%, S = 24.8% and O = 49.6%. Find the empirical formula of the anhydrous and crystalline salt. PROBLEM 2 How much quantity of zinc will have to be reacted with excess of dilute HCl solution to produce sufficient hydrogen gas for completely reacting with the oxygen obtained by decomposing 5.104 g of potassium chlorate? PROBLEM 3 A 1.85 g sample of mixture of CuCl 2 and CuBr 2 was dissolved in water and mixed thoroughly with 1.8 g portion of AgCl. After reaction, the solid which now contain AgCl and AgBr was filtered, dried and weighed to be 2.052 g. What was the % by weight of CuBr 2 in the mixture? PROBLEM 4 1.0 g of a sample containing NaCl, KCl and some inert impurity is dissolved in excess of water and treated with excess of AgNO 3 solution. A 2.0 g precipitate of AgCl separate out. Also sample is 23% by mass in sodium. Determine mass percentage of KCl in the sample. PROBLEM 5 A one gram sample containing CaBr 2 , NaCl and some inert impurity was dissolved in enough water and treated with excess of aqueous silver nitrate solution where a mixed precipitate of AgCl and AgBr weighing 1.94 g was obtained. Precipitate was washed, dried and shaken with an aqueous solution of NaBr where all AgCl was converted into AgBr. The new precipitate which contain only AgBr now weighed to be 2.4 g. Determine mass percentage of CaBr 2 and NaCl in the original sample. PROBLEM 6 Sulphur combines with oxygen to form two oxide SO 2 and SO 3 . If 10 g of S is mixed with 12 g of O 2 , what mass of SO 2 and SO 3 will be formed, so that neither S nor oxygen will be left at the end of reaction? PROBLEM 7 An aqueous solution of ethanol has density 1.025 g/mL and it is 8.0 M. Determine molality m of this solution. PROBLEM 8 An aqueous solution of acetic acid has density 1.12 g/mL and it is 5.0 m. Determine molarity (M). PROBLEM 9 Octane is a component of gasoline. Incomplete combustion of octane produces some CO along with CO 2 and H 2O, which reduces efficiency of engine. In a certain test run, 1.0 gallon of octane is burned and total mass of CO, CO 2 and H 2O produced was found to be 11.53 kg. Calculate efficiency of the engine, density of octane is 2.65 kg/gallon. PROBLEM 10 The formula of a hydrated salt of barium is BaCl 2 ⋅ xH 2O. If 1.936 g of this compound gives 1.846 g of anhydrous BaSO 4 upon treatment with H 2SO 4 , calculate x. PROBLEM 11 A mixture of CuSO 4 ⋅ 5H 2O and MgSO 4 ⋅ 7H 2O was heated until all the water was driven-off. If 5.0 g of mixture gave 3 g of anhydrous salts, what was the percentage by mass of CuSO 4 ⋅ 5H 2O in the original mixture? PROBLEM 12 A sample of clay contain 15% moisture, and rest are CaCO 3 and non-volatile SiO 2 . This on heating loses part of its moisture, but CaCO 3 is completely converted into CaO. The partially dried 4 Problems in Chemistry sample now contain 7.35% moisture and 51.5% SiO 2 . Determine mass percentage of CaCO 3 in the original sample. PROBLEM 13 Chlorine dioxide (ClO 2 ), has been used as a disinfectant in air conditioning systems. It reacts with water according to the reaction: ClO 2 + H 2O → HClO 3 + HCl In an experiment, a 10.0 L sealed flask containing ClO 2 and some inert gas at 300 K and 1.0 atmosphere pressure is opened in a bath containing excess of water and all ClO 2 is reacted quantitatively. The resulting solution required 200 mL 0.9 M NaOH solution for neutralization. Determine mole fraction of ClO 2 in the flask. PROBLEM 14 Potassium salt of benzoic acid (C 6 H 5COOK) can be made by the action of potassium permanganate on toluene as follows: C 6 H 5CH 3 + KMnO 4 → C 6 H 5COOK + MnO 2 + KOH + H 2O If the yield of potassium benzoate can’t realistically be expected to be more than 71%, what is the minimum number of grams of toluene needed to achieve this yield while producing 11.5 g of C 6 H 5COOK? PROBLEM 15 Manganese trifluoride can be prepared by the following reaction: MnI 2 ( s) + F2 ( g ) → MnF3 + IF5 What is minimum number of grams of F2 that must be used to react with 12.0 g of MnI 2 if overall yield of MnF3 is no more than 75%. PROBLEM 16 A compound containing Ca, C, N and S was subjected to quantitative analysis and formula mass determination. A 0.25 g of this compound was mixed with Na 2CO 3 to convert all Ca into 0.16 g CaCO 3 . A 0.115 g sample of compound was carried through a series of reactions until all its S was changed into SO 2– 4 and precipitated as 0.344 g of BaSO 4 . A 0.712 g sample was processed to liberate all of its N as NH 3 and 0.155 g NH 3 was obtained. The formula mass was found to be 156. Determine the empirical and molecular formula of the compound. PROBLEM 17 A 0.2 g sample, which is mixture of NaCl, NaBr and NaI was dissolved in water and excess of AgNO 3 was added. The precipitate containing AgCl, AgBr and AgI was filtered, dried and weighed to be 0.412 g. The solid was placed in water and treated with excess of NaBr, which converted all AgCl into AgBr. The precipitate was then weighed to be 0.4881 g. It was then placed into water and treated with excess of NaI, which converted all AgBr into AgI. The precipitate was then weighed to be 0.5868 g. What was the percentage of NaCl, NaBr and NaI in the original mixture. PROBLEM 18 A mixture of NaI and NaCl when heated with H 2SO 4 produced same weight of Na 2SO 4 as that of original mixture. Calculate mass percentage of NaI in the original mixture. PROBLEM 19 Ammonia is manufactured by the reaction of N 2 and H 2 . An equilibrium mixture contains 5.0 g of each N 2 , H 2 and NH 3 . Calculate mass of N 2 and H 2 present initially and maximum amount of NH 3 that can be produced. PROBLEM 20 Consider the following reactions: XeF2 + F2 → XeF6 and XeF6 + —( CH 2 —CH 2— ) n → —( CF2 —CF2 — ) n + HF + XeF4 Determine mass of F2 ( g ) required for preparation of 1.0 kg fluorinated polymer. 5 Problems PROBLEM 21 2.5 g of a sample containing Na 2CO 3 ; NaHCO 3 and some non-volatile impurity on gentle heating loses 12% of its weight. Residue is dissolved in 100 mL water and its 10 mL portion required 15 mL 0.1 M aqueous solution of BaCl 2 for complete precipitation of carbonates. Determine mass percentage of Na 2CO 3 in the original sample. PROBLEM 22 2.0 g of a sample containing NaCl, NaBr and some inert impurity is dissolved in enough water and treated with excess of AgNO 3 solution. A 3.0 g of precipitate was formed. Precipitate on shaking with aqueous NaBr gain 0.76 g of weight. Determine mass percentage of NaCl in the original sample. PROBLEM 23 Based on the following information, determine value of x and y: AgNO3 (CH 3 ) x AlCl y → xCH 4 ( g ) + yCl – + Al 3+ → AgCl( s) 0.643 g 0.222 g 0.996 g PROBLEM 24 An organic compound containing C, H, O, N and Cl was analyzed and 0.15 g of sample on combustion produced 0.138 g of CO 2 and 0.0566 g of H 2O. All the nitrogen in different 2.0 g sample of compound was converted into NH 3 which was found to weigh 0.238 g. Finally the chlorine in a 0.125 g sample of compound was converted to Cl – and by reacting with AgNO 3 , 0.251 g AgCl was obtained. Deduce the empirical formula of the starting organic compound. PROBLEM 25 A 5.0 g sample of felspar containing Na 2O, K 2O and some inert impurity is dissolved in dilute HCl solution and NaCl and KCl formed are separated by fractional crystallization. During crystallization some less soluble impurities also comes out. Mass of NaCl, KCl and impurity accompanying these salts was found to be 6.47 g. Solid crystal was then re-dissolved and required 300 mL of 0.3 M AgNO 3 for complete precipitation of chlorides. The precipitate thus, obtained was found to contain 4.23% insoluble impurity. Determine mass percentage of Na 2O and K 2O in the original sample. PROBLEM 26 Potassium chlorate (KClO 4 ) is made in the following sequence of reactions: Cl 2 ( g ) + KOH → KCl + KClO + H 2O KClO → KCl + KClO 3 KClO 3 → KClO 4 + KCl What mass of Cl 2 is needed to produce 1.0 kg of KClO 4 ? PROBLEM 27 Titanium oxide (TiO 2 ) is heated in stream of hydrogen to give water and a new oxide Ti x O y . If 1.598 g TiO 2 produces 1.438 g Ti x O y , what is the formula of new oxide. PROBLEM 28 A solution of copper sulphate that contain 15% CuSO 4 by weight has a density of 1.169 g/mL. 25 mL portion of this solution was reacted with excess of ammonia solution to form a dark blue solution. When cooled, filtered and dried, 6.127 g of dark blue solid was obtained. A 0.195g solid was analyzed for ammonia and required 30.63 mL of 0.1036 M HCl solution to reach the equivalence point. In a separate analysis, 0.200 g was heated at 110°C to drive off water, producing 0.185 g of anhydrous material. Deduce formula of the compound crystallized out from blue solution assuming that it contain only one copper atom per formula unit. Also determine the percentage yield of crystallization process. PROBLEM 29 0.1152 g of a compound containing carbon, hydrogen, nitrogen and oxygen are burned in oxygen. The gases produced are treated further to convert nitrogen containing product into N 2 . The resulting mixture of CO 2 , H 2O and N 2 is passed through a CaCl 2 drying tube, which gains 0.09912 g. The gas stream was then bubbled through water where the CO 2 forms H 2CO 3 . Titration of this solution required 28.8 ml 0.3283 M NaOH solution to reach the phenolphthalein end point. The excess O 2 was If combustion of 236 kg of a saturated hydrocarbon produces as much CO 2 as required for production of 1000 kg of urea. In one series of experiments. Deduce molecular formula of the starting compound.001 M standard solution in . PROBLEM 30 Pb(NO 3 ) 2 and KI reacts in aqueous solution to form an yellow precipitate of PbI 2 .0 atmosphere is required. Deduce empirical formula of the crystal. CO 2 for the above reaction is prepared by combustion of hydrocarbons. cooling to 0°C to precipitate solid NaHCO 3 and the filtering to remove the solid leaving soluble impurities in solution. Determine percentage purity of original sample.4 g Na 2C 2O 4 yielded 1. PROBLEM 38 An ore of iron contain FeS and non-volatile impurity. 0. 5 g of X forms 5.6 Problems in Chemistry removed by reaction with copper metal and the N 2 was collected in a 225 mL measuring bulb where it exerted a pressure of 65. A 0. Transmittance of a 0.12 mm of Hg at 25°C. but the total mass of the two was held constant at 5.295 L of H 2 ( g ) measured at 400K and 1. 3. If a 250 g impure sample of NaHCO 3 was purified by this method by dissolving first in 250 mL water at 60°C and then crystallizing NaHCO 3 from 100 mL water at 0°C.628 g of a mixture of two compounds of X. Determine mass percentage of FeS in ore. PROBLEM 37 A 100 g solution was prepared by dissolving 46 g CuSO 4⋅xH 2O in 54 g of water and mole fraction of CuSO 4 in solution was found to be 0.88 Y forms a reddish brown lower sulphide on heating the mineral in stream of H 2 ( g ).23 g UO 2 (C 2O 4 ) ⋅ xH 2O. Determine weight percentage of uranium in the original sample and x. PROBLEM 34 When iodine was added to liquid chlorine in cold condition. What maximum mass of PbI 2 can be produced in the above experiment ? PROBLEM 31 An element X react with hydrogen leading to formation of a class of compounds that is analogous to hydrocarbons.861 g of AgCl. The solubility of NaHCO 3 in water at 60°C is 164 g/L. in which Y is in + 2 state. Its solubility in cold water at 0ºC is 69 g/L. Determine molar mass of X. In one experiment. Roasting of this ore converts all FeS into Fe 2 O3 and a 4% loss in weight was observed.05. deduce molecular formula of hydrocarbon. orange crystal of a compound separate out. Some NaHCO 3 that remain in solution is not recovered. A 1. PROBLEM 36 Sodium bicarbonate can be purified by dissolving it in hot water (at 60°C). To convert 10 g Argyrodite completely. The residue are Ag 2S and H 2S. The amount of chlorine in a sample of crystal was determined by precipitating AgCl.0 g of an unknown polymeric material was dissolved in 100 mL of CCl 4 and transmittance of this solution was found to be 72%. Determine molar mass of Y and empirical formula of mineral. In a separate analysis. PROBLEM 35 Urea is manufactured on large scale by passing CO 2 (g ) through ammonia solution followed by crystallization. The mass-ratio of silver and Y in the compound is. PROBLEM 32 The mineral Argyrodite is a stoichiometric compound that contain silver. Determine x.467 g sample of crystal gave 0.0 g sample of ore on treatment with nitric acid yielded 1. XH 4 and X 2 H 6 in the molar ratio of 2 : 1. PROBLEM 39 Optical measurement is a very efficient method of determining molar mass of unknown material. 150 g NaHCO 3 was recovered. the masses of two reactants varied.48 g UO 2 (NO 3 ) 2 which on further treatment with 0.0 g. m( Ag) : m(Y ) = 11. the molar mass of this compound was found to be 146 g mol –1 . sulphur (– 2) and an unknown element Y ( + 4). PROBLEM 33 Uranium is isolated from its ore by dissolving it as UO 2 (NO 3 ) 2 and separating it as solid UO 2 (C 2O 4 ) ⋅ xH 2O. filtering to remove insoluble impurities. dried and weighed to be 0. What is the smallest and largest volume of 0. Determine mass percentage of oxalic acid in the original sample.1 M HCl solution.7 Problems the same solvent.5 g sample containing oxalic acid and some inert impurity was dissolved in enough water and volume made up to 250 mL. At last. A 0. PROBLEM 40 shown below. Find the percentage of CaO and MgO on oven dried basis and percentage of them and H 2O on air dried basis. 8. The solution was . Determine percentage composition of the salt mixture. The magnesium is precipitated as MgNH 4 PO4 which finally ignited to 0.12 g/cm 3 . Determine molar mass of the mother cell if density of the smallest cell is 1.0 g on air dried basis.0 mL of acid was required to reach the equivalence point.5 g Mg 2 P2O 7 .9437 g. that weigh 0. What weight of Fe 2O 3 would be obtained if 0. The smallest cells are uniform cylindrical in shape with diameter of 120 Å and each cell is 6000 Å long.2 g/cm . determine molar mass.15 M AgNO 3 solution that may be used for complete precipitation of chloride from a 0. PROBLEM 42 A sample of rock taken for analysis weigh 1. After drying for one hour at 110°C.3g sample of the mixture which may contain any one or all of the constituents? ACID-BASE TITRATION PROBLEM 45 A 1. under identical experimental condition was 60%.5g.5 g sample containing P2O 3 and some inert impurity was dissolved in enough water and boiled gently where P2O 3 disproportionated quantitatively into PH 3 and H 3 PO 4 . KCl and NaCl. The calcium is precipitated as oxalate but weighed as CaSO 4 .75 g BaSO 4 .2 g of the sample were ignited in air? PROBLEM 44 A chloride mixture is prepared by grinding together pure BaCl 2⋅2H 2O. The resulting solution was then treated with stoichiometric amount of CaCl 2 just needed for precipitation of oxalate as CaC 2O 4 . the sample weigh 0. Solution was filtered off and filtrate was finally titrated against 0. PROBLEM 46 A 1. the above neutral solution was treated with excess of AgNO 3 solution and AgCl obtained was washed. Determine molar mass of unknown polymer. PROBLEM 41 A mother cell disintegrate into sixty identical cells and each daughter cell further disintegrate into 24 smaller cells.4305 g. A 20 mL portion of this solution was then mixed with 30 mL of an alkali solution. PROBLEM 43 A sample is a mixture of Mohr’s salt and (NH 4 ) 2 SO 4 . A crystalline polymer molecule is uniform prismatic in shape with dimensions as 300 Å 100Å 3 If density of this polymer is 1.5 g sample on treatment with excess of BaCl 2 solution gave 0. magnesium metaphosphate. which contains 21%. What was the percentage by mass of nitrogen? How does this mass compare with percentage mass of nitrogen calculated from glycine (H 2 NCH 2COOH)? PROBLEM 51 In a reaction.8 Problems in Chemistry further boiled for some time to let-off all PH 3 ( g ) and finally cooled to room temperature and diluted to 100 mL.05 g sample was treated in such a way that all nitrogen in it was converted into ammonia.57 mL 0. The PH 3 gas is burnt completely to P2O 5 using air. This ammonia was added to 50 mL of 0. In an another . Determine mass percentage of P2O 3 in the original sample.05 M H 2SO 4 solution to reach the phenolphthalein end point. Li = 7.15 M HCl solution. Ca(HCO 3 ) 2 and NaCl was dissolved in 100 mL water and its 10 mL portion required 10 mL 0. 5. dissolved in enough water to give 50 mL solution. The excess acid remaining in the solution required 30. 3. PROBLEM 52 9.3 M NaOH solution. PROBLEM 47 2. To 0. An another 10 mL portion of the same stock solution required 32.486 g of the mixture.4 g Mg was initially reacted with calcium orthophosphate. Ignore volume change due to addition of indicator. PROBLEM 50 An amino acid isolated from a piece of animal tissue was believed to be glycine.27 M NaOH to reach the equivalence point.0 g of a mixture containing NaHCO 3 . Excess alkali required 11. calcium oxide and oxygen gas. The reaction mixture was heated to expel all SO 2 and then 25 mL of the reaction mixture was titrated with 0.37 g of solid residue.11 mL of the base.0 N NaOH solution. 7. PROBLEM 54 5. Determine mass of Na 2CO 3 and NaHCO 3 per litre of solution. A 10 mL portion of this solution was then mixed with 20 mL 0.3 g of a mixture containing Li 2CO 3 .5 g of a mixture containing CaCO 3 .06 M NaOH solution for complete neutralization. The titration required 13.08 M H 2SO 4 solution.1 M KOH.0 mL of acid was required to reach the end point A 5.0 g of a monobasic.0 mL 0. Determine mass percentage of CaCO 3 and Ca(HCO 3 ) 2 in the original mixture. The residue is dissolved in 200 mL water.4 mL 0.1 M HCl solution to reach the equivalence point. PROBLEM 49 A mixture was known to contain both KNO 3 and K 2SO 3 . NaHCO 3 . Calculate the volume of air at STP required for combustion. Na = 23. A 10 mL portion of this solution is mixed with 15 mL of a normal HCl solution.0 mL 0. In an another experiment.53 mL of acid was required to reach the end point.05 M HCl solution. was added 50 mL of 0. if 2.5 N NaOH solution to reach the equivalence point. Determine the volume of the acid solution that would be required to make this solution neutral. Determine the mass percentage of NaHCO 3 and Na 2CO 3 in the original mixture.0 g of the same acid is burnt completely and CO 2 produced is absorbed completely in 500 mL of a 2. calcium orthophosphate on heating with magnesium produced calcium phosphide. A 10 mL portion of the resulting solution is treated with excess of BaCl 2 to precipitate all carbonate and finally titrated with 0. 10 mL portion of this solution is mixed with few drops of phenolphthalein indicator and titrated against 0.0 mL portion of this solution was then taken for further analysis and a few drops of methyl orange was added to it and finally titrated against same acid solution.05 M H 2SO 4 solution for back titration. Calculate mass percentage of K 2SO 3 in the mixture. NaCl and Na 2CO 3 is dissolved in 500 mL water and its 10 mL portion required 12. The excess acid required 12 mL 0. A 0. by volume of oxygen.5 N H 2SO 4 solution. saturated carboxylic acid is dissolved in 100 mL water and its 10 mL portion required 8.35 mL of the same acid solution to reach the methyl orange end point. PROBLEM 48 A solution contain both Na 2CO 3 and NaHCO 3 . Phosphide on hydrolysis produces PH 3 gas. All volumes are measured at STP. PROBLEM 53 4. Na 2CO 3 on strong heating produced 7. 4 g of a pure monobasic organic acid is burnt completely in excess of oxygen and CO 2 evolved is absorbed completely in one litre of an aqueous solution of NaOH.63 mL 1.15 mL 1.0 N HCl to reach the end point in presence of phenolphthalein indicator.15 M NaOH solution. and resulting solution required 22.022 N HCl for complete neutralization. PROBLEM 58 40 g of a sample of caustic soda containing NaOH.0 N HCl solution to reach the equivalence point.55 mL HCl of same strength to reach the end point.0 N HCl to reach the end point in presence of methyl orange indicator. PROBLEM 60 One gram sample of a saturated hydrocarbon is burned completely and liberated CO 2 was absorbed in a 1. The other half required 123. what mass of AgCl will precipitate out? PROBLEM 57 One litre solution of alkali is prepared by dissolving impure solid of alkali which contain 5% Na 2CO 3 and 8% CaCO 3 and 10% NaCl. A 10 mL portion of the extract required 12 mL 0.25 M NaOH solution to reach the equivalence point.6 mL 0.98 mL HCl of same strength. by titrating it against a standardized acid as follows: Co(NH 3 ) x Cl 3 ( aq ) + HCl → NH +4 ( aq ) + Co 3+ ( aq ) + Cl – ( aq ) A 1.2 N NaOH solution. Na 2CO 3 and inert impurity is dissolved in water to prepare 1. A 10 mL portion of this solution required 14. excess of BaCl 2 is added. Calculate mass percentage of Na 2CO 3 and NaHCO 3 in the mixture. On the other hand its other 50 mL portion required 19 mL 0. deduce the empirical formula of this acid and strength of original NaOH solution. If the organic acid contains 25% oxygen by weight.33 mL 1.44 mL 1. Determine mass percentage of each component.204 N NaOH and then excess of BaCl 2 is added resulting in precipitation of all carbonate as BaCO 3 . monobasic carboxylic acid was burned and liberated CO 2 was passed through a concentrated solution of NaOH. In a separate analysis. A 25 mL portion of this solution required 22. PROBLEM 61 2. Determine molecular formula of the hydrocarbon.0 L 0.45 mL 0. To 25 mL another solution. Determine formula.202 N HCl using methyl orange as indicator. If the reaction mixture at equivalence point is treated with excess of AgNO 3 solution.72 mL 1.5 mL of a normal HCl solution to reach the phenolphthalein end point. PROBLEM 59 1. Determine the mass percentage of each component in the original mixture.025 M H 2SO 4 solution for neutralization.0 g of a saturated. PROBLEM 62 2. 10 mL portion of the same stock solution is mixed with 10 mL 0. Calculate weight of alkali dissolved initially. Excess NaOH required 12.9 Problems experiment. An another 10 mL portion of the same solution required 18 mL of the same HCl solution to reach the methyl orange end point. .0 litre solution. Deduce formula of acid and determine mass of NaOH present initially.5 M HCl to reach the equivalence point. A 25 mL portion of this solution required 23.58 g complex required 23.8 mL of a 0. The resulting solution was separated into two equal half and analyzed.1 M HCl solution for back titration. PROBLEM 56 A complex of cobalt with ammonia is analyzed for determining its formula. To the resulting solution. A 10 mL portion of this solution required 9. PROBLEM 55 6. One half required 71. Filtrate required 9.5 M H 2SO 4 solution for neutralization.5 g of a sample containing Na 2CO 3 and NaHCO 3 is dissolved in 100 mL of water. Calculate mass percentage of NaOH and Na 2CO 3 in the original sample.5 g of a mixture containing NaHCO 3 . excess of BaCl 2 crystals was added and the solution was filtered off to free from BaCO 3 . 25 mL portion of the same stock solution is mixed with 30 mL 0. Na 2CO 3 and NaCl is dissolved in 100 mL water and its 50 mL portion required 13. 0.1 M NaOH solution to reach the equivalence point. PROBLEM 67 A 3.1 N HCl solution.1 M HCl solution to reach the end point using phenolphthalein indicator. if methyl orange is used as indicator.05 M NaOH solution. but now against 0.0 mL of a NaOH solution to make the solution neutral. PROBLEM 66 10. Determine mass percentage of Na 2CO 3 . Determine mass percentage of ammonium nitrate in the original sample. Determine mass percentage of each component in the mixture. In a separate analysis. end point is indicated only when Na 3 PO 4 is converted into Na 2 HPO 4 while. PROBLEM 69 A mixture containing LiHCO 3 . 42.38 mg of a diprotic acid (containing (C. A 10 mL portion of this solution was then treated with 20 mL 0. In another experiment. PROBLEM 64 2.86 mL 0. Other half was titrated in presence of methyl orange indicator and 80 mL H 2SO 4 solution of same strength was required to reach the end point. H and O) is burned completely and all CO 2 was absorbed in 100 mL of alkali solution. A 10 mL portion of the resulting solution required 3. NaHCO 3 . 20 mL of base was required to reach the equivalence point. NaHCO 3 and CaCO 3 on gentle heating loses 48. 20 mL acid was required to reach the equivalence point.168 g of the same acid required 16. 5.0 g of a crystal of CaCO 3 is dissolved in 50 mL water and then mixed with 50 mL of a HCl solution. 10 mL portion of the same stock solution is titrated with 0.1 N KOH solution.0 g of this mixture was dissolved in 100 mL water and its 10 mL portion . 11. PROBLEM 68 In neutralization titration of Na 3 PO 4 . 5. Determine mass percentage of all components in the mixture.64 mL of alkali was required to reach the end point.725 g of a mixture of K 2C 2O 4 .077 g of barium phosphate precipitate was obtained.0 g mixture containing Na 3 PO 4 . Deduce formula of the acid and determine molarity of alkali solution used initially.1 M NaOH solution to reach the end point. The resulting solution was then mixed with excess of AgNO 3 solution resulting in formation of 0. In an experiment a 4.5 M HCl solution to reach the end point using methyl orange as indicator.10 Problems in Chemistry PROBLEM 63 2. KHC 2O 4 and H 2C 2O 4 ⋅ 2H 2O is dissolved in 100 mL H 2O and its 10 mL portion is titrated with 0.18 mL 0. if phenolphthalein is used as indicator.572 mL 0.1 M HCl solution using phenolphthalein indicator.0 g sample containing Na 2CO 3 .0 g of this mixture was heated gently and residue was dissolved in 100 mL water. NaHCO 3 and NaCl in the original sample. PROBLEM 70 A mixture containing LiHCO 3 . In a separate experiment.306 g of AgCl precipitate. end point appear only when Na 3 PO 4 is converted into H 3 PO 4 . NaCl and Na 2CO 3 on gentle heating loses 26.0 g sample containing NH 4 NO 3 .005 M H 2SO 4 solution to reach the phenolphthalein end point. 10 mL portion of the same stock solution required 23. The resulting solution is separated into two-half and one-half required 55 mL 0. PROBLEM 65 A 1. The resulting solution is boiled to remove all CO 2 and its 10 mL portion required 8. (NH 4 ) 3 PO 4 and some inert impurity was dissolved in 100 mL water its 10 mL portion required 15 mL 0. Determine mass percentage of each component in the mixture. In an experiment.5% of its weight. In a separate analysis. Determine molarity of both NaOH and HCl solution. 10 mL of the same stock solution was treated with excess of BaCl 2 solution and 0.2 M H 2SO 4 solution. Na 2 HPO 4 and NaH 2 PO 4 is dissolved in 50 mL water and its 10 mL portion required 24. Also 20 mL of original HCl solution is equivalent to 96 mL of NaOH solution.4% of its weight.32 mL of acid solution was required to reach the end point.4 mL 0. The solution was filtered-off and filtrate was again titrated. NaCl and some inert impurity was dissolved in 100 mL of water and its 10 mL portion was titrated against 0.125 M NaOH solution to reach the end point. 34 mL 0. NaHCO 3 .1 N NaOH solution to reach the end point. Determine mass percentage of CaCO 3 and NaHCO 3 in the original sample.2 M NaOH to reach the end point. Determine mass percentage of Na 2C 2O 4 and H 2C 2O 4⋅2H 2O in the original sample. produced Na 2CO 3 and some NaHCO 3 .25 g of solid residue.0 g of a sample of CaCO 3 . was heated strongly where CaCO 3 and NaHCO 3 .0 g of the same mixture required 10 mL 0. the residue obtained after heating of the original sample was dissolved in water and treated with excess of BaCl 2 .1 M Ba(OH) 2 solution was required to just restore the pink colour of solution. PROBLEM 73 A one gram sample containing NaOH as the only basic substance and some inert impurity was left exposed to atmosphere for a very long time so that part of NaOH got converted into Na 2CO 3 by absorbing CO 2 from atmosphere.25 M HCl solution to reach the equivalence point when methyl orange was used as indicator.00 mL 0.04 M acidified permanganate solution to reach the equivalence point. Methyl orange was then added and titration continued with HCl of same strength where 15 mL HCl was required to reach the final end point.5 M NaOH solution.1 M HCl solution. 20 mL portion of the same stock solution required 26. A 20 mL portion of this solution was mixed with 50 . An additional 9.985 g of BaCO 3 precipitate. PROBLEM 72 2. inert impurity. giving 0. PROBLEM 76 A 1. Titration of a blank taken through the entire procedure used 22. Determine mass percentage of all components present in the mixture. PROBLEM 74 The monochloroacetic acid (ClCH 2COOH) preservative in a 100 mL of carbonated beverage was extracted by shaking with dimethyl ether and then returned to aqueous solution as ClCH 2COO – by extraction with 1.0 g of a mixture containing NaCl. On the other hand.0 M HCl was required to reach the phenolphthalein end point. In a 3rd experiment. oxalic acid dihydrate and some inert impurity was dissolved in 100 mL water and its 20 mL portion required 23. The resulting sample was dissolved in water and volume made upto 100 mL.3 mL 0. NaOH was little less than the stoichiometric requirement therefore.0452 M AgNO 3 solution where the following reaction occurred: ClCH 2COOH + AgNO 3 + H 2O → HOCH 2COOH + H + + NO –3 + AgCl( s) After filtering the AgCl. titration of filtrate required 10. Determine mass percentage of NaOH in the original sample and mass percentage of Na 2CO 3 in the sample after exposure to atmosphere. NaHCO 3 and some volatile. Determine mass percentage of each component in the mixture. Calculate weight in mg. In a separate experiment.0 g of the same mixture was dissolved in 100 mL water and required 10 mL 1. This solution was acidified and treated with 50 mL 0. NH 4 NO 3 and some inert impurity was dissolved in water and volume made upto 100 mL. were decomposed into CaO and Na 2CO 3 respectively and all CO 2 gas produced in decomposition was absorbed in a 50 mL NaOH solution.11 Problems was treated with 10 mL 0.053 M HCl solution to reach the end point. The resulting solution was titrated first in presence of phenolphthalein indicator and 5. Na 2CO 3 and CaCO 3 on gentle heating reduces to 4.98 mL of same NH 4SCN solution.1 N HCl solution to reach the end point.0 g of a sample containing sodium oxalate. PROBLEM 71 5. A 100 mL portion of this solution required 16 mL 0. In a separate analysis. 20 mL portion of the same solution was taken alongwith phenolphthalein indicator and mixed with 50 mL of 0. of ClCH 2COOH in the beverage sample. The resulting solution was then treated with excess of BaCl 2 solution resulting in precipitation of all carbonates as BaCO 3 .43 mL of an NH 4SCN solution. 1. 1.0 mL 1. PROBLEM 75 2. In a separate analysis. Precipitate was separated out by filtration and filtrate required 15. CO 2 during reaction with NaOH.0 M NaOH.67 mL 0.5 g sample containing (NH 4 ) 2 SO 4 . Determine percentage purity of perchlorate sample and volume of 0. In an analysis.101 M FeSO 4 . Cr 2O 2– 7 and VO 3 then treated with 25 mL of 0.01. tribasic carboxylic acid required 68.1 M NaOH solution. The solution was then treated with HCl and – resulting solution still containing Fe 3+ .0 g impure sample containing [Zn(NH 4 ) 4 ]Cl 2 and some inert impurity was treated with 15 mL of 1 M NaOH solution where all complex is converted into Na 2 [Zn(OH) 4 ] . HCl and H 2O. The removal of H 2O generate oxygen gas and KOH and this KOH in the subsequent step remove CO 2 as KHCO 3 .0 g of a sample of rock salt was dissolved in 100 mL H 2SO 4 solution. In a separate analysis 20 mL of the above solution required 50 mL 0.5 M HCl required to neutralize the above solution. In a separate analysis.12 Problems in Chemistry mL 0. PROBLEM 82 3. REDOX TITRATION PROBLEM 83 A sample of chrome-vanadium steel weighing 2. 32 mL of the original stock solution on treatment with excess of BaCl 2 solution produced 0. .2 g of a salt with their empirical formula K x H y (C 2O 4 ) z was dissolved in 50 mL of water and its 10 mL portion required 11.04 M NaOH for complete neutralization.1 M H 2SO 4 solution in a separate analysis. 15 mL of the stock solution required 20 mL 0. 2. Determine empirical formula of the salt.25 g of a saturated. Assume room conditions to be at 1.4 mL of a 0.0 kg of an impure sample of KO 2 is just sufficient to remove all CO 2 and H 2O from a closed room of dimension 10 m × 5 m × 3m.0 atmosphere and 300 K and mole fraction of CO 2 in that room is 0. PROBLEM 77 A 1. Determine molecular formula of acid. (b) If the last solution obtained after neutralization was treated with excess of AgNO 3 . Excess sulphuric acid left in 20 mL of this solution required 40 mL 0.466 g BaSO 4 precipitate. vanadium to VO 3 and Mn to MnO 4 . N 2 .750 M NaOH solution to reach the equivalence point.00 mL of a 0. 6 (a) Determine percentage purity. Determine mass percentage of NH 4 NO 3 and (NH 4 ) 2 SO 4 in the original sample. PROBLEM 79 Impure phosphoric acid for use in the manufacture of fertilizer is produced by the reaction of sulphuric acid on phosphate rock of which a principal component is Ca 3 (PO 4 ) 2 and rest are silica and other inert impurity.2475 M KOH to reach the equivalence point. what weight of AgCl would have been produced? PROBLEM 78 1. The excess base 1 required 10 mL M HCl solution for back titration. the – – chromium to Cr 2O 2– 7 .00 mL 1/28 M H 2SO 4 solution for complete neutralization. PROBLEM 80 A 10 g sample of ammonium perchlorate containing some inert impurity was mixed with 3 g Al powder where all perchlorate reacted to produce Al 2O 3 . Determine mass percentage of Ca 3 (PO 4 ) 2 in rock-sample.0 g was dissolved in a mixture of sulphuric acid and just sufficient oxidant was added to raise the oxidation state of iron to Fe 3+ . A 30 mL aliquot of this resulting solution required 9. In a separate analysis. All HCl was absorbed in 100 mL 1 M NaOH solution. Determine mass of this KO 2 required to neutralize a 100 mL 0. 5.1 M HCl solution to reach the equivalence point. PROBLEM 81 Potassium superoxide (KO 2 ) is utilized in closed system breathing apparatus to remove CO 2 and water from exhaled air.02 M NaOH for back titration. 7225 g sample of salt was dissolved in 100 mL of pure water. dissolved 1 g of it in water and precipitated the calcium by adding sodium oxalate. Cr = 52] PROBLEM 84 A sample of crude uranium oxide is known to be contaminated with iron.25 g sample containing CaC 2O 4 .02 M KMnO 4 for titration of excess of oxalate. Calculate mass percentage of contamination if the iron were present as Fe 2O 3 in a sample of crude oxide containing 100 g of U 3O 8 .Problems 13 This resulted in reduction of dichromate and VO –3 to Cr 3+ and VO 2+ in the solution respectively. wishing to analyze the mixture. The titration required 22 mL of the KMnO 4 solution. Calculate freezing point of an aqueous solution which is 5% (w/V) of the above mixture.0 N H 2SO 4 solution to reach the equivalence point if phenolphthalein was used as indicator. the crude oxide were dissolved and reduced with Zn to yield a solution containing U 4+ and Fe 2+ . 25 mL of solution was taken and excess oxalate was removed by extraction. PROBLEM 87 Both CaCl 2 and NaCl are used to melt ice and snow on roads in winter. The calcium oxalate was then carefully filtered. a process requiring 0. 10 mL this permanganate solution is equivalent to 4. K f of water is 1. Fe 2+ and VO 2+ in the solution was then titrated with 0. Calculate mass percentage of PbO 2 and Pb 3O 4 in the original sample. Atomic mass of U = 238. KMnO 4 solution oxidised Fe 2+ to Fe 3+ and U 4+ to UO 2+ 2 . A 10 mL portion of this solution required 8. PbO 2 and some inert impurity is dissolved in 250 mL dil. (c) Moles of Fe 2+ consumed by Cr 2O 2– 7 .02236 M KMnO 4 .1 M KMnO 4 solution. To determine the extent of contamination. In an another experiment. Calculate the following quantities: (a) Moles of Fe 2+ in 25 mL sample of standard FeSO 4 solution.3 mg of U 3O 8 .86 mL to reach the equivalence point.7 g of Na 2C 2O 4 was added so that all lead converted into Pb 2+ . Deduce the formula of the salt. A certain company was marketing a mixture of these two compounds for this purpose.0 mL 0. this required 10 mL of a permanganate solution for oxidation of Pb 2+ to Pb 4+ .23 mL.48 mL 5 V H 2O 2 solution. A small amount of Fe 2+ was then added to again reduce the VO –3 produced by KMnO 4 back to VO 2+ and this then titrated directly with 0.86 K kg mol –1 . [Atomic mass of Pb = 207] PROBLEM 86 An unknown cupric salt with formula Cu x (CO 3 ) y (OH) z is analyzed to determine the exact formula. A 20 mL aliquot of this solution was treated with cupferron which precipitated all uranium and the resulting precipitate on ignition yielded 423. PROBLEM 88 A 4. A further 20 mL sample was treated with 0. Another 50 mL portion was titrated using methyl orange as indicator and 15 mL acid of same strength was required.02236 M KMnO 4 and required 12. A 50 mL portion of this solution required 10 mL 1.024 M KMnO 4 solution and consumed 27. dissolved in dilute sulphuric acid.6 mL to reach the equivalence point. PROBLEM 85 A 5. A 1. (d) Percentage of V and Cr in the steel [Atomic weight of V = 51.0 g sample containing Pb 3O 4 . and titrated with 0. A chemist. (b) Moles of Fe 2+ titrated with 12.6 mL of standard KMnO 4 . Na 2C 2O 4 and some inert impurity is heated gently so that CaC 2O 4 decomposed as: CaC 2O 4 → CaO + CO( g ) + CO 2 ( g ) . HNO 3 solution and 2. 50 mL sample of the same stock solution is treated with Zn-amalgum and the resulting solution required 17.28 ×10 –3 M acidified KMnO 4 solution.25 M HCl to reach the equivalence point.225 g sample of mineral is ground and boiled with 75 mL 0. PROBLEM 95 A driver is arrested and asked to pass “breath analyzer” test. Determine mass percentage of MnO 2 in the sample. Also determine the molar ratio of oxygen to NO 2 in the gaseous products given off. A 20 mL portion of this solution required 3. In an experiment 15 g mixture of NaNO 3 and Mg(NO 3 ) 2 was heated until no more gas were evolved.5 mL of exhaled air is then bubbled into a spectrometer cell containing 3 mL 0.34 mL of the oxidizing agent solution was required to reach the end point.1 M K 2Cr 2O 7 solution. In another experiment 10. Determine the mass percentage of Na 2C 2O 4 in the original sample. The excess reagent required 10.5 M HCl to reach the phenolphthalein end point while the other half solution required 50 mL 0. In a separate experiment same mass of the same sample is dissolved into 100 mL dilute HCl solution and its 10 mL portion required 10 mL 0. A 0. sodium oxalate and NaHC 2O 4 and is dissolved in 100 mL of water and its 10.5 mL of permanganate solution of same strength. The unreacted ICl was then treated with excess of KI. How many mL of this same KMnO 4 solution would be required to oxidise 25 mL 0.FeCl 3 ⋅ 6H 2O and inert impurity is dissolved in dilute sulphuric acid and volume made up to 100 mL. After the reaction is complete. the solution is cooled and titrated with 2.75 mL of 0. Determine mass of I 2 that would have been required with 100. 45 mL KMnO 4 solution is required to react with 50 mL 0. Determine mass percentage of FeCl 3 ⋅ 6H 2O in the original sample.05 M oxalic acid solution. The water soluble part of residue was used for analysis and dissolved in 1. Liberated iodine required 40 mL 0.4% after bubbling the sample . NO 2 and oxygen. PROBLEM 94 The mass percentage of MnO 2 in a sample of mineral is determined by reacting with As 2O 3 in acid solution.0 mL portion of the same stock solution required 24 mL 0.0 mL portion required 16 mL 0.5% initially and 43. PROBLEM 92 A 0.1 M hypo solution.02 M acidified KMnO 4 solution.25 N Na 2C 2O 4 solution. Determine mass percentage of each nitrate in the mixture. 16.3 g containing K 3 [Fe(C 2O 4 ) 3 ] ⋅ 3H 2O.14 Problems in Chemistry All gaseous products were passed through a NaOH solution where following reaction occurred quantitatively: 2NaOH + CO 2 ( g ) → Na 2CO 3 The resulting solution is separated into two equal part (by volume) and one part required 30 mL 0.025% (w/V) K 2Cr 2O 7 solution.005 M acidified KMnO 4 solution to reach the equivalence point.0 g oil if I 2 were used in place of ICl.1 M ICl solution. 10 mL portion of this solution was reacted with 20 mL 0. A sample consisting 56.25 M NaOH to reach the equivalence point.1 g sample containing oxalic acid dihydrate. Determine the mass percentage of all components in the original mixture. PROBLEM 89 In acidic solution. PROBLEM 91 A 6. In an another experiment.5 M HCl solution to reach the methyl orange end point.0125 M As 2O 3 solution.0 litre water. The transmittance of the solution was 41.1 N K 2C 2O 4 solution in alkaline medium where KMnO 4 is reduced to MnO 2 .127 g of an unsaturated oil was treated with 25 mL of 0. PROBLEM 93 Alkali metal nitrate on heating decomposes to metal nitrite and oxygen whereas alkaline earth metal on heating decomposes into metal oxide.00 mL 0. PROBLEM 90 A sample weighing 0. 0 g sample containing KO 2 and some inert impurity is dissolved in excess of aqueous HI solution and finally diluted to 100 mL.04 M KI solution where copper precipitate as CuI and iodide ion is oxidized into I –3 . K sp.Problems 15 through the reaction cell. PROBLEM 98 Cuprous ion is known to disproportionate quantitatively in acid medium. Calculate mass percentage of Cu 2O in the original sample.0 L of water and transferred to a beaker containing 50 mL H 2O. PROBLEM 100 One gram of an impure sample of NaCl was dissolved in water and treated with excess of AgNO 3 solution.0 M aqueous solution of Br 2 . The precipitate is then filtered. The resulting solution is freed from bromide ion by extraction and excess of OH – neutralized by acidifying the solution. The solution is filtered off and 8. formed undergo decomposition into Ag and Cl 2 ( g ) and latter disproportionate into chlorate (V) and chloride ions and chloride is re-precipitated due to presence of excess of AgNO 3 . Now.0 mL portion was acidified by adding excess of sulphuric acid solution and . PROBLEM 99 To a 10 mL 1.5 × 10 –8 and of CaC 2O 4 = 2. Calculate percentage purity of oxalate sample. If the original precipitate was 60% decomposed and final precipitate weigh 1.33 M alkaline solution of KMnO 4 and refluxed so that all cyanide is converted into cyanate (OCN – ). Determine the concentration of alcohol in the blood and state whether or not the driver should be charged with drunk driving. A 10 mL portion of this solution is taken for analysis. determine mass percentage of NaCl in original sample. Liberated iodine required 20 mL 2.3 g pure KI crystal is added to filtrate. filtered. PROBLEM 101 0. Determine mass % of KO 2 in the original sample.34 × 10 –9 . To this solution was added 50 mL 0. The precipitate AgCl thus. PROBLEM 97 1. PROBLEM 102 One gram of an unknown sample of NaCN is dissolved in 50 mL 0.5 gram. of BaC 2O 4 = 1. The solution is acidified to solublise the precipitate and finally titrated with 0.0 N Na 2S 2O 3 solution. Determine mass percentage of CuCO 3 in the original sample. The reaction mixture was cooled and its 5. Find the composition of the initial mixture. Ammonia is added to the solution to raise the pH than an excess of Na 2C 2O 4 is added to precipitate the metals. A 3.94 mL of oxidizing agent solution was required to reach the end point. excess of an oxidizing agent is added to filtrate and liberated iodine required 10 mL 1. excess of NaOH is added so that all Br 2 disproportionated to Br – and BrO –3 .0 g sample of Cu 2O is dissolved in dilute H 2SO 4 solution. The solution is filtered off and filtrate is boiled till all I 2 is expelled off.5 g of an impure CaC 2O 4 sample. PROBLEM 96 A sample of 0.4 M Na 2S 2O 3 solution to reduce the liberated iodine. washed with 1. A total of 13. made free from I –3 and treated with excess of acidic permanganate solution.4 g of a sample containing CuCO 3 and some inert impurity was dissolved in diute sulphuric acid and volume made up to 50 mL.5 m M sodium thiosulphate solution to reach the end point. It is known that the alcohol content in blood stream is 2300 times higher than in exhaled air and that the legal limit is 80 mg of alcohol per 100 mL of blood. This caused precipitation of CuI with evolution of I 2 .3657 g powder containing only Ba(NO 3 ) 2 and Ca(NO 3 ) 2 are dissolved in 50 mL water.05 M KMnO 4 solution. The solution is filtered off and 20 mL of filtrate required 15 mL 0. The resulting solution is just sufficient to react with 1. 325 kPa.0 mL 0.0 atm and 27°C.0 g of He having average velocity 4 × 10 2 ms –1 is mixed with 12. Titrated solution was then treated with excess of aqueous solution of AgNO 3 where all chloride precipitates as AgCl and weighed to be 0. GASEOUS STATE PROBLEM 105 6. PROBLEM 107 Calculate pressure exerted by 22. Precipitate was re-dissolved into 100 mL 1.1 M acidic dichromate solution for back titration. A 38 mL of oxalate solution was required to reach the end point. Solution is filtered off and filtrate and precipitate were analyzed separately.0 g sample containing CaOCl 2 and NaOCl is dissolved in 100 mL water and its 10 mL portion was titrated against 0.0 g of CO 2 in 0.0 g of Ne 20 having the same average velocity.1325 Mpa and 273 K is 0. what would be the pressure inside the tank after 10 days assuming temperature of the lab to be 27°C. Calculate radius of He atom assuming negligible ‘a’.1 M acidified solution of Na 2C 2O 4 . 10 mL of oxalate solution was required to reach the end point. Determine mass percentage of NaCN in the original sample. If the initial leak rate was found to be 1 g s –1 and initial pressure inside the 7.16 Problems in Chemistry finally titrated with 19.67 cc/ mol.0 M acidified solution of Na 2C 2O 4 and excess of oxalate required 50.28 m 3 tank was 17180 kPa.73 mL 0. PROBLEM 103 5.0 mL of a pure liquid toluene is dissolved in 100 mL of dilute alkaline KMnO 4 solution and refluxed so that all toluene is oxidized into benzoic acid and a dark brown precipitate of MnO 2 is formed.15 M acidified solution of Na 2C 2O 4 . On the other hand 10.1 M FeSO 4 solution.5 mL of filtrate was acidified by adding excess of sulphuric acid and titrated with 0. What is the average kinetic energy per mole in the mixture? PROBLEM 106 The valve of a commercial cylinder of N 2 gas was left slightly open so that small amount of gas leaked into the laboratory. Determine mass percentage of CaOCl 2 and NaOCl in original sample.011075 times its molar volume at 101. The leak rate was proportional to the pressure difference (internal pressure one atm).5 L bulb at 300 K assuming it to be real gas with a = 363 kPaL2 mol –2 and b = 42. PROBLEM 109 A gas mixture containing 5% by mass of butane and 95% by mass of Ar (40) is to be prepared by allowing gaseous butane to fill an evacuated 40 L cylinder at 1. PROBLEM 104 A 2. Calculate mass of Ar that gives the desired composition and total pressure of the final mixture. PROBLEM 108 Molar volume of He at 10. Determine density of liquid toluene and molarity of original permanganate solution.287 g. PROBLEM 110 Cl 2O 7 gas decomposes as: Cl 2O 7 → Cl 2 + O 2 A partially decomposed gaseous mixture is allowed to effuse through a pin-hole and the gas coming . PROBLEM 120 Calculate the van der Waal’s constants for ethylene.05 L mol –1 . whereas expected pressure was 1.0 m. PROBLEM 115 A flask containing 2. The rate of effusion of collected gaseous mixture was found to be 0. determine the average translational kinetic energy possessed by a molecule. (a) Determine (i) Molecular weight (ii) Molar volume (iii) Compression factor (Z) of the vapour (iv) Which forces among the gas molecules are dominating.60.5 litre flask at 273 K exert a pressure of 0. The compressibility factors found to be 1. Determine final pressure and final number of moles in each flask. Calculate the total weight of the gas inside the flask. PROBLEM 116 In a spherical glass flask A of radius 1. Now the He-flask is placed in a thermostat at 200 K and N 2 -flask in another thermostat at 400 K. A sample of neon gas has 22 Ne = 90% and 20 Ne = 10% by moles. 25% enrichment of 20 Ne would be achieved? PROBLEM 112 The density of vapour of a substance at 1. The mole fraction of the O 2 was found to be 0.45 times rate of effusion of pure oxygen gas. PROBLEM 119 One litre of a gas at 300 atm and 473 K is compressed to a pressure of 600 atm and 273 K.5 at 273 K and one atmosphere and TB of the gas is 107 K.PC = 50 atm. PROBLEM 111 Proportion of a lighter isotope in a gaseous mixture containing both heavier and lighter isotopes is increased by successive effusion of the gas mixture.Problems 17 out initially was analyzed.375 respectively at the initial and final states. The vapour effuses through a small hole at a rate of 1. there was a rubber balloon B containing some N 2 ( g ).0 atm has the gas behaved ideally. PROBLEM 117 A partially decomposed PCl 5 (g ) along with its dissociation product is subjected to diffusion study and the gases coming out initially collected in an another flask. b = 0.072 and 1.0 atm and 500 K is 0. Now 50 g H 2 ( g ) is further added to A. there was another rubber balloon C containing some oxygen gas.0 moles of He gas at 1.35 k/ m 3 . containing 300 g H 2 (g ). calculate the pressure correction factor for two moles of a gas confined in a four litre flask that exert a pressure of 11 atmosphere at 300 K. the attractive or repulsive? (b) If the vapour behaves ideally at 1000 K. At 27°C. PROBLEM 114 For a van der Waals’ gas Z (compressibility factor) was found to be 1. it was found that the balloon B had radius 60 cm and of C was 30 cm. Determine the degree of dissociation of PCl 5 ( g ) in the original sample. Volume of the nitrogen flask is three times volume of He-flask. PROBLEM 113 Using van der Waals’ equation of state. PROBLEM 118 One mole of a monoatomic gas confined in a 22. TC = 282 K. Determine value of a and b.33 times faster than oxygen under similar condition. Inside B.0 atm and 300K is connected to another flask containing N 2 ( g ) at the same temperature and pressure by a narrow tube of negligible volume. Determine the van der Waal’s constants ‘a’ and ‘b’ and Boyle’s temperature (TB ). Calculate the final volume. . what would be the volume of B and C. In how many stages of successive effusion. determine the degree of dissociation.98 atm. PROBLEM 132 One mole of a van der Waal’s gas at 0°C and 600 atmosphere occupies 0. what will be the partial pressure of He and methane after 1.Determine the molar mass of X assuming that gases were injected at same temperature and through the pin-hole of identical geometry. Calculate the volume of a gm mole of the gas at 27°C and 5 atmosphere pressure.18 Problems in Chemistry PROBLEM 121 The second Virial coefficient of an imperfect gas is 2 × 10 –2 (L/ mol) 2 .0 hours due to diffusion through a pin-hole in the steel chamber.0 atm if it is a van der Waal’s gas with a = 6. B = – 2. calculate the density of moist air at 25°C and 1.45 g/cc and its TC = 300 K. PROBLEM 126 Using van der Waals’ equation of state. The vapour pressure of water at 25°C is 23. a = 3. and ‘a’.42 centilitre/mol. At 0°C. PROBLEM 125 An unknown gas (X) at 2.0 metre long glass tube and the first collision between X and Ar occurred at a distance of 38 cm from Ar-end.075 L. Assume rate of diffusion to be linear function of gas pressure and inverse function of square root of molar masses. where Vm is the molar volume and P is the gas pressure in atmosphere.0 atmosphere in 4.6 atm L2 mol –2 . If an equimolar mixture of He and methane gas at 20 atmosphere and the same temperature are confined in the same chamber. PROBLEM 127 An equation of state for a non-ideal gas can be written as: PVm = A + BP + CP 2 . If . Under the experimental condition.0 atmosphere when the relative humidity is 60%. PROBLEM 130 At what temperature.98 × 10 –5 in litre atmosphere unit.71 atm L2 mol –2 and b = 56. PROBLEM 124 The Virial equation for ethane gas is given by PV = RT + BP . calculate pressure developed by 100 g of CO 2 contained in a volume of 5.0 to 1. determine the pressure at which PV-P curve will attain minimum.0 hour. PROBLEM 128 A modified form of van der Waal’s equation of state for 1. b = 44 cm 3 mol –1 .76 mm of Hg.0 atmosphere and Ar (40) at 1. How near can the centres of the two molecules approach each other? PROBLEM 123 For carbon dioxide. three moles of SO 2 will occupy 10 litre at a pressure of 15. Determine its van der Waal’s constants. B = – 0. PROBLEM 122 The van der Waal’s constant ‘b’ of a gas is 4.0 mole of gas is given as: α P + (V – β) = RT TV 2 Deduce expression for the first Virial coefficient (B) and Boyle’s temperature in term of α and β if Virial equation of state is: PV B C = 1 + + 2 +… RT V V PROBLEM 129 Assuming that dry air contain 79% N 2 and 21% O 2 by volume.0 atmosphere were injected simultaneously from the two ends of a 1. PROBLEM 131 Pressure of He gas confined in a steel chamber drops from 4.1814 L/ mol.0 litre at 40°C.4 cm 3 mol –1 . Also compare this value with that calculated using ideal gas law and determine the percentage deviation from ideality.879 × 10 –2 and C = 14. critical density is 0. Calculate volume of one mole of ethane at 10 atm. – =k dt M If k for the diffusion of methane gas is 2. . contain methane gas at 5.0 atm. PROBLEM 140 What will be the temperature difference needed in a hot air balloon to lift 1. Determine number of moles of each component present at 500 K. k is a constant. PROBLEM 134 A long cylindrical glass tube.1 mm of Hg. ammonia is partially decomposed into N 2 and H 2 and a pressure measurement at this point gave 48. Assume that the volume of balloon is 100 m 3 .m.0 atm.0 mole of an ideal gas is injected into the system. sealed and heated to 500 K. some KClO 3 was decomposed and 36. determine final pressure inside the flask assuming negligible heat capacity of flask and negligible volume of solid NH 4Cl. One bulb is placed in a 200 K thermostat bath and other in a 300 K thermostat bath and then 1.024 L mol –1 . PROBLEM 136 1. In a typical experiment.5 atmosphere.0 atmosphere on one side and He gas at 2.0 litre capacity each. NH 3 ( g ) + HCl( g ) → NH 4Cl( s).s.0 kg weight.0 atmosphere and 300 K is connected to another 800 mL flask containing HCl(g) at 8.0 atmosphere. PROBLEM 135 At a given condition of temperature.0 atmosphere. the temperature of atmosphere is 25°C and pressure is 1. determine compressibility factor (Z) and predict the type of force dominating among the gas molecule.0 atmosphere and 300 K by means of a narrow tube of negligible volume and gases were allowed to react quantitatively as: CH4 5. rate of change of r. PROBLEM 133 A one litre flask containing NH 3 (g ) at 2. of He gas is twice the rate of change of absolute temperature. determine time after which pressure of methane chamber will drop to 4. Find the pressure in the two flasks. At this temperature. PROBLEM 138 A narrow tube of negligible volume connects two evacuated bulb of 1.6 moles of ammonia gas at 300 K is taken in a 2.0 atmospheres.0 litre flask. n Determine isothermal compressibility for an ideal gas at 1.0 atmosphere on the other side of the disc as shown in the diagram below: Disc is permeable to both gases and rate of diffusion is directly proportional to the gas pressure and inversely proportional to square root of molar masses as: dp P where.0 atmosphere.00 mL oxygen gas was collected over water at 23°C. Find the volume of the dry oxygen at 0°C and 1. He 2. ∆H = – 43kJ/ mol If heat capacity of HCl(g) CV is 20 JK –1 mol –1 . PROBLEM 139 Isothermal compressibility (κ ) of a gas is defined as: 1 ∂V κ =– V ∂P T . equipped with a porous disc at the centre. Average molar mass of air is 29 amu.5 ×10 –2 second –1 . PROBLEM 137 Decomposition of KClO 3 produces oxygen gas and KCl solid. Determine rms of He in the given condition. The laboratory barometer reads 751 mm and vapour pressure of water at 23°C is 21.19 Problems b = 0. What percentage of heat is used to raise the temperature of the water? PROBLEM 145 How much heat can be produced from a reaction mixture of 50 g of iron (III) oxide and 25 g of aluminium in the thermite reaction: Fe 2O 3 ( s) + 2Al( s) → Al 2O 3 ( s) + 2Fe( s). THERMOCHEMISTRY PROBLEM 144 The specific heat capacity of water is 4. PROBLEM 142 The van der Waals’ constant ‘a’ is a correction factor to the ideal gas law for intermolecular force of attractions within the substance. given standard enthalpy of combustion of ethyne. benzene.464. 0.2107. ∆H = – 851.86 kJ PROBLEM 148 An important reaction that occurs in the atmosphere is NO 2 ( g ) → NO( g ) + O( g ) Which is brought about by the sunlight.20 Problems in Chemistry PROBLEM 141 Using van der Waals’ equation of state. Ne and steam. Calculate the heat that must be supplied to a 500 g copper kettel containing 450 g of water to raise its temperature from 25°C to the boiling point of water.22 kJ N 2 ( g ) + 4H 2 ( g ) + Cl 2 ( g ) → 2NH 4Cl( s) ∆H = – 628. Ne and steam. 5. 0. – 1300. How mucy energy the sun to cause it must supply? Given. 18. ethane and hydrogen.00 and 24. dissociation energy of oxygen = 498 kJ/ mol and NO( g ) + O 3 ( g ) → NO 3 ( g ) + O 2 ( g ) ∆H = – 200 kJ 3O 2 ( g ) → 2O 3 ( g ) ∆H = 285. find pressure at which the PV vs P curve acquires minima for 1.06 with gases benzene.5 kJ/ mol PROBLEM 146 Calculate the reaction enthalpy for the hydrogenation of ethyne to ethane.38 J( ° C) –1 g –1 . a =1.1154 and 0. b and c determine the enthalpy change of this reaction: 3 CH 4 ( g ) + O 2 ( g ) → CO( g ) + 2H 2O( g ) 2 (a) CH 4 ( g ) + 2O 2 ( g ) → CO 2 ( g ) + 2H 2O( g ) ∆H ° = – 802 kJ/ mol .0 mole of oxygen gas at 0°C. with the gases: toluene.017. PROBLEM 143 The van der Waals’ constant ‘b’ is a correction factor to the ideal gas law for the intrinsic volume of the molecule.4 kJ PROBLEM 149 Using reaction a.36 L2 atm mol –2 . – 1560 and – 286 kJ/mol respectively. and b = 32 cm 3 mol –1 . Match the following values of ‘a’ ( L2 atm mol –1 ): 0.18 J(° C) –1 g –1 and that of copper is 0. Match the following values of ‘b’(L mol –1 ): 0. toluene. PROBLEM 147 Calculate the reaction enthalpy for the synthesis of HCl(g) from the following data: NH 3 ( g ) + HCl( g ) → NH 4Cl( s) ∆H = – 176 kJ N 2 ( g ) + 3H 2 ( g ) → 2NH 3 ( g ) ∆H = – 92.1463.0305. 3 kJ/mol. chlorine and hydrogen are 314. C—H = 415.E of C==O =196. Calculate P-Cl and P-H bond energy. Use this data to estimate the magnitude of the resonance energy of benzene. H—H = 436 kJ/mol respectively. Calculate the average bond energy of an N—H bond in ammonia if ∆H ° f of ammonia is – 46 kJ/mol. Also calculate the bond energy of C==C bond in trans-2-butene. Enthalpy of hydrogenation of ethylene is – 132 kJ/mol. Average bond energy of C—H = 415.21 Problems (b) CH 4 ( g ) + CO 2 ( g ) → 2CO( g ) + 2H 2 ( g ) ∆H ° = + 206 kJ/ mol (c) CH 4 ( g ) + H 2O( g ) → CO( g ) + 3H 2 ( g ) ∆H ° = + 247 kJ/ mol PROBLEM 150 The bond energy of H 2 (g ) is 436 kJ/mol and that of N 2 (g ) is 941. ∆H v° of benzene = 30. C==C = 600. (ii) Enthalpy of formation of benzene(l) = 49 (iii) Enthalpy of vaporization of benzene(l) = 30 + 3H2(g) (iv) Resonance energy of benzene(l) = – 152 (v) Heat of formation of gaseous atoms from the elements in their standard states H = 218. O==O = 118. the molar heat of formation of SO 2 and H 2O are – 296. ∆H v (H 2O) = 11 kcal / mol.E. O—H =110.E. resonance energy of C 6 H 6 ( l) = – 152 kJ/ mol. C—C = 80 and C—H = 98 kcal/mol respectively. determine C==C bond energy.81 and – 285. 2H 2S( g ) + Fe( s) → FeS 2 + 2H 2 ( g ) ∆H ° = – 137 kJ/ mol 3 H 2S( g ) + O 2 ( g ) → H 2O( l) + SO 2 ( g ) ∆H ° = – 562 kJ/ mol 2 Calculate heat of formation of H 2S( g ) and FeS 2 ( s) at 25°C. Calculate the B.8 kcal/mol. of H 2 ( g ) is 436 kJ/mol and of C—H = 415 kJ/ mol.8 and of cyclohexane is 33 kJ/mol. The heat of combustion of 1-butene is – 649. Using the information from the following reactions. C = 715. PROBLEM 153 The standard molar enthalpy of formation of cyclohexane (l) and benzene (l) at 25°C are – 156 and + 49 kJ/ mol respectively. and the heats of atomization of phosphorus. Determine the heat of combustion of trans-2-butene.5 kJ/mol respectively. PROBLEM 157 Enthalpy of polymerization of ethylene and acetylene into corresponding polymers are – 86 kJ/ mol and – 148 kJ/mol respectively. ∆H = – 950 and +1771cal/ mol respectively. 121 and 216. B. of C—C and C==C. PROBLEM 155 Using the data (all values are in kJ/mol at 25°C) given below: (i) Enthalpy of polymerization of ethylene = – 72. PROBLEM 154 For the reaction cis-2-butene → trans-2-butene and cis-2-butene → 1-butene. PROBLEM 152 At 25°C. Given B.83 kJ respectively. [ A : 331 and 590 kJ/mol] PROBLEM 156 Calculate energy of aromatization of cyclohexane according to the following reaction. . The standard enthalpy of hydrogenation of cyclohexene (l) at 25°C is – 119 kJ/ mol. both cyclohexane and benzene are in liquid state: Given. bond energies: C—C = 348. sublimation energy of C(gr) is 717 kJ/mol. PROBLEM 151 The heat of formation of PCl 3 and PH 3 are 306 kJ/mol and 8 kJ/mol respectively. Determine ∆HComb of decane.P.0 km swimming. PROBLEM 165 Standard molar enthalpy of formation of hydrazine liquid (N 2 H 4 ) is 50 kJ/mol. First electron affinity of C 2 ( g ) = – 315 kJ/ mol.G. PROBLEM 163 Standard molar enthalpies of formation of H 2O(l) and H 2O 2 (l) are – 285 and – 200 kJ/mol respectively and their molar enthalpies of vaporization are 41 and 60 kJ respectively. Given: enthalpy of combustion of methane = – 890 kJ/ mol. determine N—N bond energy in N 2 H 4 . If enthalpy of atomization of O 2 ( g ) is 298 kJ/mol. . If enthalpy of vaporization of N 2 H 4 is 18 kJ/mol. produces acetylene. contains 90% propane and 10% methane by weight.P.3-butadiene = – 2841 kJ/ mol. Enthalpy of sublimation of C( s) = 718 kJ/ mol.22 Problems in Chemistry PROBLEM 158 ∆HComb of methane and ethane are – 210 kcal/mol and – 368 kcal/mol respectively. Second electron affinity of C 2 ( g ) = + 410 kJ/ mol. C(gr ) = – 394 kJ/ mol.G. C==C = 615 kJ/ mol.E. Average N—H and H—H bond energies are 393 and 436 kJ/mol respectively.P. PROBLEM 162 A swimmer breaths 20 times in one minute when swimming and inhale 200 mL of air in one breath. Enthalpy of sublimation of Ca( s) = 179 kJ/ mol. C==C = 615 kJ/ mol. Bond energy of C 2 ( g ) = 614 kJ/ mol. H 2 ( g ) = – 285 kJ/ mol Bond enthalpy : C—C = 348 kJ/ mol. ∆H °f of C 2 H 2 ( g ) = + 75 kJ ∆H °v of C 6 H 6 ( l) = + 45 kJ B. If combustion of L. Second ionization energy of Ca(g) 1143 kJ/mol. C 2 H 2 = – 1300 kJ/ mol and CO( g ) = – 285 kJ/ mol. Inhaled air contain 20% O 2 by volume and exhaled air contain 10% O 2 by volume. C C = 348 kJ/ mol PROBLEM 160 Consider the following thermodynamic data: Enthalpy of formation of CaC 2 ( s) = – 60 kJ/ mol. determine bond energy of O—O bond. If all oxygen are consumed in combustion of glucose in the body and 25% of energy obtained from combustion is available for muscular work.3-butadiene using the following information: Enthalpy of combustion : 1. Also standard enthalpy of formation of cyclobutene =130 kJ/ mol. Draw a clear Born-Haber cycle and determine lattice energy of CaC 2 ( s). CO(g) and H 2O( l). C ≡≡C = 930 kJ/ mol. PROBLEM 166 Using following standard enthalpies: ∆H °f HF( aq ) = – 329 kJ/ mol ∆H ° f H 2O( l) = – 285 kJ/ mol.G. NH 3 ( g ) = – 46 kJ/ mol. First ionization energy of Ca(g) = 590 kJ/ mol. PROBLEM 164 Determine resonance energy of 1. Determine the maximum distance this swimmer can swim in one hour if 100 kJ energy is required for 1. calculate the heat evolved by combustion of 100 g of L. C 3 H 8 = – 2220 kJ/ mol. PROBLEM 161 Normal L. PROBLEM 159 Determine resonance energy of benzene [C 6 H 6 (l)] from the following information : ∆H °f of C 6 H 6 ( l) = + 49 kJ. Standard molar enthalpy of combustion of glucose is – 2880 kJ/ mol and body temperature is 37°C. ∆H = – 56 kJ/ mol. ∆H ° f of (C 2 H 5 ) 2 S 2 ( g ) = – 202 kJ/ mol and ∆H °Sublimation of S( s) = 223 kJ/ mol.36°C. calculate heat of neutralization of HCl Vs NH 4OH.23 Problems ∆H ° f F – ( aq ) = – 320 kJ /mol and H + ( aq ) + OH – ( aq ) → H 2O( l).) → Fe 2+ ( aq. O—H = 463. B. ∆H °Vaporization of acetic acid and water are 52 and 41 kJ/mol respectively. Given ∆H ° f of (C 2 H 5 ) 2 S( g ) = – 147 kJ/ mol. PROBLEM 172 ∆H ° f of enthalpy of combustion of C 2 H 5OH( l) = – 66 kcal/ mol. CH 3OCH 3 ( g ) = – 348 kcal/ mol. bond dissociation energy of N 2 ( g ) and H 2 ( g ) are 946 and 436 kJ/mol respectively. O==O = 498. ∆H ° f of C 2 H 6 = – 84 kJ/ mol. Assume terminal B—H bonds have same strengths. (C—H) = 410 kJ/mol. PROBLEM 167 From the following reactions and thermal information at 25°C: 3 2Fe( s) + O 2 → Fe 2O 3 ( s) ∆H ° = – 821. Bond energies in kJ/mol. ∆H °Sublimation C(gr) = 717 kJ/ mol. Which bonds would you expect to be longer-terminal or bridged one? . Determine enthalpy of neutralization of HF against a strong base. PROBLEM 169 Determine S—S bond energy. If the heat capacity of calorimeter content is 1316.) + H 2 ( g ) ∆H ° = – 87. C—C = 348. PROBLEM 170 Given the following standard molar enthalpies: of ∆H ° f of CH 3CN( g ) = 88 kJ/ mol. Determine C—C and C ≡≡N bond energies.4 N HCl is neutralized with excess of NH 4OH in a bomb calorimeter which results in a temperature rise of 2. Determine mean B H bond enthalpies in each case. C==O = 728.) 2 2 1 H 2 ( g ) + O 2 ( g ) → H 2O( l) 2 Calculate ∆H ° for the reaction : ∆H ° = 0 ∆H ° = – 285 kJ FeO( s) + 2H + ( aq ) → H 2O( l) + Fe 2+ ( aq ) PROBLEM 168 A 150 cc portion of 0.E. Determine enthalpy of the following isomerization reaction: C 2 H 5OH( l) → CH 3OCH 3 ( g ) PROBLEM 173 The standard enthalpies of formation of BH 3 (g ) and B2 H 6 (g ) are 100 kJ and 36 kJ per mol respectively and the enthalpies of formation of B( g ) and H( g ) are 563 kJ mol –1 and 218 kJ mol –1 respectively. C—H = 410.7 J/°C.8 kJ 1 H ( g ) → H + ( aq. ∆H ° f of water is – 68 kcal/mol and ∆H ° f of CO 2 ( g ) = – 94 kcal/ mol. C—O = 352. PROBLEM 171 Determine standard state enthalpy of the following reaction: CH 3COOH( l) → CH 4 ( g ) + CO 2 ( g ) Given ∆H °Combustion CH 4 = – 860 kJ/ mol. estimate enthalpies of the three centre B H B bonds in B2 H 6 .4 kJ 2 1 2FeO( s) + O 2 → Fe 2O 3 ( s) ∆H ° = – 284 kJ/ mol 2 Fe( s) + 2H + ( aq. 0 atm pressure. Bond dissociation energies of O 2 ( g ) and C==O( g ) are 498 kJ mol –1 and 743 kJ mol –1 respectively.4 kJ mol –1 . explain the difference in calculate and observed value of enthalpies. for the various solid modification of CaCl 2 in the indicated quantities of water are shown below: . while that of CuSO 4 ⋅ 5H 2O is –11. C P of water is 418 . Now pressure was applied on the gaseous mixture which results in conversion of 0. Also. determine the enthalpy of combustion of CO( g ) and compare it with actual value. Assume air to be 21. ∆H f° of CO 2 ( g ) and H 2O( l) are −394 kJ mol –1 and –286 kJ mol –1 respectively. PROBLEM 177 With the following informations. PROBLEM 181 At 25°C. CO 2 and H 2O are: −104 kJ mol –1 . –3920 and –289 kJ/mol respectively. Also. Density of ethanol is 0. the heat of solution of anhydrous CuSO 4 in a large volume of water is −66.495 kJ. ∆H f° of propane. PROBLEM 175 Assuming that mileage of an automobile gets is directly proportional to the heat of combustion of fuel.6 kJ N 2 ( g ) + 12 O 2 ( g ) → NO( g ) 2 NO( g ) + 12 O 2 ( g ) → NO 2 ( g ) ∆G° = − 34. calculate how many times farther an automobile could be expected to go on one litre gasoline than on 1. ∆H f° of ethanol and octane are −278 kJ mol –1 and –208. 1 …(i) ∆G° = 86.7025 gmL–1 ). Assume gasoline to be pure n-octane (ρ = 0. determine standard state Gibb’s free energy of formation of N 2O 4 ( g ). Determine heat of reaction: CuSO 4 ( s) + 5H 2O → CuSO 4 ⋅ 5H 2O( s) PROBLEM 182 The integral heats of solution at 25°C. The gases are then cooled rapidly back to 25°C.1 mole of N 2 into NH 3 .77 kJ …(iii) Standard state enthalpy of formations of CO( g ) and CO 2 ( g ) are −111 kJ mol –1 and –394 kJ mol –1 respectively. Jg –1 K –1 . – 394 kJ mol –1 and –286 kJ mol –1 respectively. Determine the net heat change in this process given the following bond enthalpies: N 2 ( g ) = 944 kJ mol –1 .7893 gmL–1 .82 kJ …(ii) 2NO 2 ( g ) → N 2O 4 ( g ) ∆G° = − 5.7 J/ ° C. PROBLEM 176 10 g of propane was burnt in air at 30°C and 1. calculate heat of neutralization.0 mole of H 2 (g ) taken in a flask at 25°C and heated to 450°C. If the heat capacity of Dewar and its contents after the reaction is 1316. determine volume of air required for combustion process.36°C. Supposing that there is a double bond in CO as two double bond in CO 2 . H 2 = 436 kJ mol –1 and average N H bond energy = 388 kJ mol –1 . determine resonance energy of benzene( l).0 litre ethanol. C 6 H12 (l) (cyclohexane) H 2 (g ) are –3268. PROBLEM 180 A 150 cc portion of 0. determine final temperature of water. If enthalpy of hydrogenation of cyclohexane is –120 kJ/mol.4 NHCl is neutralized with an excess of NH 4OH in a Dewar vessel with a resulting rise in temperature of 2.24 Problems in Chemistry PROBLEM 174 Enthalpy of combustion of C 6 H 6 (l).00 kg of water at 30°C.00% O 2 . PROBLEM 178 PROBLEM 179 One mole of N 2 (g ) and 3.044 kJ mol –1 . If all the heat produced from combustion of 10 g of propane was transferred to 8. predict the most likely structure.06 kJ …(iv) Determine enthalpies of the following hydration reactions: (a) CaCl 2 (s) + 2H 2O → CaCl 2 ⋅ 2H 2O (b) CaCl 2 ⋅ 2H 2O + 2H 2O → CaCl 2 ⋅ 4H 2O (c) CaCl 2 ( s) + 6H 2O → CaCl 2 ⋅ 6H 2O PROBLEM 183 The enthalpy of following reactions at 25°C are: (i) Na( s) + 12 Cl 2 ( g ) → NaCl( s) ∆H ° = − 410. N N = 163 kJ mol –1 and N == N = 409 kJ mol –1 . N 2 = 944 kJ mol –1 . If its standard enthalpy of formation is 1072 kJ mol –1 .E.925 kJ …(i) …(ii) CaCl 2 ⋅ 4H 2O + 396 H 2O → CaCl 2 (400 H 2O) ∆H 3° = − 7.21 kJ From the above thermal data.5 kJ (iv) 1 2 H 2 ( g ) + 12 Cl 2 ( g ) → HCl( g ) ∆H ° = − 92.3 kJ CaCl 2 ⋅ 2H 2O + 398 H 2O( l) → CaCl 2 (400 H 2O) ∆H 2° = − 41.6 kJ (ii) H 2 ( g ) + S( s) + 2O 2 ( g ) → H 2SO 4 ( l) ∆H ° = − 810.0 hour. What (i) + H2 ∆H° = – 38 kJ (ii) + 2H2 ∆H° = – 170 kJ minimum hours would he need to jog if he wished to lose 0.25 Problems CaCl 2 ( s) + 400 H 2O( l) → CaCl 2 (400 H 2O) ∆H1° = − 4.56 kJ (iii) 1 2 H 2 ( g ) + 12 Cl 2 ( g ) → HCl( g ) (iv) H 2 ( g ) + 12 O 2 ( g ) → H 2O( l) ∆H ° = − 92. Given: B. PROBLEM 186 A male burns 2000 kJ of energy while jogging for 1.4 kJ 1 (ii) 2Ag( s) + 2 O 2 ( g ) → Ag 2O( s) ∆H ° = − 30.65 kJ …(iii) CaCl 2 ⋅ 6H 2O + 394 H 2O → CaCl 2 (400 H 2O) ∆H 4° = +19. calculate the standard molar heat of formation of AgCl.21 kJ ∆H ° = − 394 kJ PROBLEM 185 Draw Lewis structures of hypothetical molecule N 6 (g ) consisting of a six membered ring of nitrogen atom.5 g fat? . PROBLEM 184 Given the following standard state enthalpies of reaction.54 kJ (iii) 2Na( s) + S( s) + 2O 2 ( g ) → Na 2SO 4 ( s) ∆H ° = −1381. If the standard heat of combustion of a typical fat is 38 kJ g –1 and only 70% energy is available for muscular activity. (i) Ag 2O ( s) + 2HCl( g ) → 2AgCl( g ) + H 2O( l) ∆H ° = − 324. determine enthalpy of the following reaction: 2NaCl( s) + H 2SO 4 ( l) → Na 2SO 4 ( s) + 2HCl( g ). PROBLEM 194 10 g of ice at 0°C are added to 20 g water at 90°C in a thermally insulated flask of negligible heat capacity. is placed in sunlight for 10 minutes. not to increase temperature. If CV = 20. What would be the work done if the reaction took place in a sealed vessel? PROBLEM 197 A balloon is 0. PROBLEM 188 From the following enthalpies values. PROBLEM 193 Calculate entropy change when 0.8 JK –1 mol –1 . how much work is done on the system at 27°C.6 JK –1 mol –1 ) at 300 K and one atmosphere is allowed to expand to double its volume and simultaneously heated to 373 K. piston fitted cylinder at 300 K is heated to 800 K as well as allowed to expand to a volume of 8 L simultaneously.5 mol of the gas is reversibly compressed from an initial volume of 2 dm 3 to a final volume of 0.26 Problems in Chemistry PROBLEM 187 Strong sunshine bombards the Earth with about 1 kJ m –2s –1 . PROBLEM 190 One mole of a monoatomic. determine surface area of beaker.6 kJ mol –1 . If 0. calculate ∆S System . If a beaker containing ethanol. 3.02 L mol –1 . PROBLEM 195 One mole of a supercooled liquid water at – 10°C and one atmosphere turns into ice at – 10°C. Calculate the work done by the liberated hydrogen gas assuming it to behave ideally. It is then filled with air isothermally and reversibly until the pressure reaches to 5 bar. determine resonance energy of C 6 H 6 (l) “Benzene”. Assume that pressure is proportional to the diameter of the balloon. THERMODYNAMICS PROBLEM 189 Suppose that a gas obeys the modified van der Waals’ equation P × (Vm – b) = RT and b = 0. What is the final temperature. Also.2 JK –1 mol –1 respectively. Assuming that all the heat is used for vaporization. Calculate change in enthalpy of the system. 100 g of zinc are caused to react with dilute sulphuric acid.5 dm 3 . The heat of fusion of ice is 6 kJ/mol. PROBLEM 191 One mole of a monoatomic ideal gas confined in a 5 L.3-cyclohexadiene is 70 kJ mol –1 . Calculate entropy change for the system. ∆S System ? C p = 75.24 g of liquid was vaporized. .5 m in diameter and contains air at 25°C and 1 bar pressure. PROBLEM 196 In an open beaker at 27°C and one atm pressure.42 and 37.42 JK –1 mol –1 . given the resonance energy of 1. ideal gas confined in a 5 L piston fitted cylinder at 300 K is heated such that its temperature increased to 400 K but at the same time gas also expanded to a volume of 8 L. The pressure is suddenly released to 10 atmosphere and gas is allowed to expand adiabatically. calculate (a) final diameter and (b) work done in the process. Calculate change in enthalpy of the system. PROBLEM 192 100 g of nitrogen gas at 300 K are held by a piston under 30 atmosphere.5 L of an ideal gas (CV =12. C p for liquid water and ice are 75. Enthalpy of vaporization is 42. ∆U and ∆H if 2. It is allowed to expand until P2 = 1 atm and V2 = 10 L. assume C vm = 2. PROBLEM 205 For a perfect gas. W. Calculate the work done on the system if the equation state is: a P + 2 Vm = RT Vm where a = 0.5 atm.0 atm. PROBLEM 199 With the temperature maintained at 0°C. 40 L to 0. the temperature of this gas falls to 250 K. calculate ∆E m and ∆H m . 40 L.00 bar to a final pressure of 2 bar. .0 moles of this gas undergoes following change of state: (a) A reversible isobaric expansion from 1.0 atm. 40 L (c) A reversible isothermal compression from 0. Calculate C p at 300 K. C v = 2. (a) How much energy is transferred to the surrounding during the expansion? (b) What is the change in internal energy and enthalpy of the gas? (c) How much heat the gas has absorbed? PROBLEM 200 A gas behaving ideally was allowed to expand reversibly and adiabatically to twice its volume. pressure increasing from 1. Construct a reversible path connecting this initial and final state as a combination of reversible isothermal expansion followed by reversible adiabatic expansion so that the final state is attained and calculate work done by the system in attaining the final state.384 m 6 Pa mol –1 PROBLEM 203 Find q. 2. PROBLEM 206 A sample of an ideal gas underwent an adiabatic expansion from 298 K.0 g of He undergoes a reversible isobaric expansion from 20 to 40 L at 0.5 R . liquids and solids are rather incompressible. 2 mole of an ideal gas are allowed to expand against a piston that supports 2.52 + 8. What are ∆U and ∆H for this process? Could the process be carried out adiabatically. A sample of this gas is initially at T1 = 300 K.0 atm.5 R? PROBLEM 207 A gas behaves ideally and its C v is given by: C v = 21. Since. 20 L to 1.2 dm 3 mol –1 .5 atm. 40 L to 1. The initial pressure of the gas is 10 bar and the final pressure 2 bar.W.8 atm pressure followed by reversible isochoric heating till pressure reaches to 1. What is the final temperature of the system and work done by the system. During this process.2 × 10 –3 T (all parameters in SI unit).42 JK –1 mol –1 .0 atm.03 dm 3 mol –3 . Its initial temperature was 25°C and C vm = (5 / 2) R .27 Problems PROBLEM 198 One mole of an ideal gas initially at 10 bar and 300 K is allowed to expand against a constant external pressure of 2. C vm = 3/ 2 R . PROBLEM 202 One mole of a gas at 100 K is compressed isothermally from an initial volume of 20 dm 3 to a final volume of 5 dm 3 . 15 bar to 2.0 bar. ∆U and ∆H.0 atm. ∆U and ∆H for the process. Calculate q.0 atm to 10.0 bar pressure.5 bar against a constant external pressure of 1. Calculate work done on the system if the equation of state of the gas is (Vm – b) P = RT with b = 0. PROBLEM 204 One mole of liquid water at 30°C is adiabatically compressed. (b) A reversible isochoric change from 1. Sketch each process on the P-V diagram and calculate : q. 20 L.0 atm. C p of H 2O( l) = 75. Depict the change of state on a P-V diagram. P1 = 10 bar and V1 = 1 L. it is a fairly approximastion to take V constant. PROBLEM 201 One mole of a gas at 300 K is compressed isothermally and reversibly from an initial volume of 10 dm 3 to a final volume of 0. 36 + 20. The gas is then expanded isothermally and reversibly to a new state C.79 ln T Calculate change in Gibb’s free energy of one mole of argon gas if it is heated at constant pressure from 25°C to 50°C. C v =1. where V is volume of V gas at each stage of expansion. 5. C v =1. 1.0 atm. Further during expansion from volume 10 L to 100 L. Depicting on a P-V diagram. γ = .0 atm until equilibrium is established. What is the change in internal energy of the system? 10 atm.5 R . and ∆S.28 Problems in Chemistry PROBLEM 208 The entropy change of argon is given to a good approximation by the expression: Sm / JK –1 mol –1 = 36. PROBLEM 210 An ideal gas expand against a constant external pressure of 2. 5. . determine the net work done in the above cyclic process.76 × 10 –2 T Calculate ∆U . determine the net work done in the cyclic process. Depicting on a P-V diagram. The gas is then cooled at constant pressure to another new state D (200 K) and finally compressed adiabatically and reversibly to A. Assume the gas to be ideal with: C p = 28. 500 K) → B Isochoric cooling Reversible Adiabatic compression B → C (300 K) → A Depicting the above mentioned change on a P-V diagram.0 bar) is expanded isothermally and reversibly to a new state B and then cooled at constant pressure to C (250 K) and finally compressed adiabatically and reversibly to A.0 bar) is heated at constant pressure to double its volume (B). If C v is expressed as: C v = 30 + 14 × 10 –3 T JK –1 mol –1 . determine W. ∆E and q. 3 PROBLEM 214 One mole of an ideal gas is subjected the following change of state: Reversible Isothermal expansion A(5. determine the net work done in the cyclic process.5 R .0 atmosphere from 20 L to 50 L and absorb 20 kJ of energy from surrounding. ∆H. PROBLEM 213 One mole of an ideal gas at state A (500 K. C v =1. the gas undergoes a change in internal energy of 420 J.0 mole of an ideal gas is allowed to expand adiabatically against a constant pressure of 4.0 atm) is cooled at constant volume to B (300 K) and then expanded isothermally and reversibly to C and finally compressed adiabatically to A. PROBLEM 209 Initially at 300 K and 10 atm pressure. 5 Sketch the change on a P-V diagram and determine the net work done in this cyclic process.5 R . How much heat is absorbed by the gas during expansion? PROBLEM 211 A gas expands against a variable pressure given by P = PROBLEM 212 Three moles of an ideal gas is heated at constant pressure of one atmosphere from 27°C to 127°C.58 + 1. PROBLEM 215 One mole of an ideal gas initially at A (300 K and 5. PROBLEM 216 One mole of an ideal gas at A (500 K. PROBLEM 226 Two moles of an ideal gas is expanded isothermally and irreversibly at 27°C from volume V1 to 2.0 atmosphere is heated to 500 K and expanded simultaneously to 36 litre. PROBLEM 223 A gaseous reactant A forms two different product in a parallel reaction B and C as follows: A → B . Determine ∆H assuming heat capacity to be independent of temperature and C v =1. PROBLEM 218 One mole of an ideal gas at 500 K and 10 bar is allowed to expand till the final pressure falls to 1. PROBLEM 222 One mole of an ideal gas is taken in a one litre sealed flask at 300 K and heated till the pressure becomes equal to 40 atmosphere.17 kJ heat is absorbed from surroundines. ∆H ° = – 3. PROBLEM 225 Two moles of NO 2 is heated at constant volume from 27°C to 127°C and C p (JK –1 mol –1 ) = 28 + 31 × 10 –3 T Determine ∆S. Determine ∆S if C v = 2.0 bar is heated from 27°C to 127°C.5 V1 and 4.5 R . ∆S ° = 10 JK –1 Discuss the relative stability of B and C on the basis of Gibb’s free energy change at 27°C.0 atmosphere.0 bar followed by reversible expansion so that final state is reached and determine final pressure of the gas.5 + 3 × 10 –3 T [JK –1 mol –1 ] and C v =1. PROBLEM 224 One mole of an ideal gas contained in a sealed flask at 1. PROBLEM 220 One mole of a gas initially at 300 K is heated to 500 K.0 atmosphere is heated as well as expanded simultaneously to 500 K and 2. ∆S surr and ∆S univ .5 R . ∆S ° = 20 JK –1 A → C . If C v = 12 + 28 × 10 –3 T (in SI unit). (b) Determine the work by reversing the order of combination in (a) and compare the two work done. Determine ∆G if: S (JK –1 ) = 10 +12 × 10 –3 T . C v =1. Determine the Gibb’s free energy change. Construct a combination of reversible path of: (a) initial adiabatic expansion followed by isothermal expansion so that final state is reached and determine the total work done. PROBLEM 219 One mole of an ideal gas at 300 K and 1.29 Problems PROBLEM 217 One mole of an ideal gas at 500 K and 10 bar. ∆H ° = – 3 kJ. Determine ∆S sys . defined by state A is allowed to expand isothermally and does a work equal to 4200 J. .5 R .0 atmosphere and final temperature falls to 250 K. PROBLEM 221 One mole of an ideal gas at 300 K and 1.6 kJ.5 R . determine ∆S. ∆G if S = 1. Construct a combination of initial irreversible expansion upto 2. PROBLEM 231 One mole of an ideal gas is subjected to the following change of state: Reversible Isothermal expansion Isochoric cooling A(500 K. 40 L) Isobaric heating Isochoric cooling Reversible Isothermal compression B → C (0.0 bar ) → B → C (250K. If 2.5 bar. C v =1.. C v =1.0 bar . The gas is then expanded isothermally and reversibly to a new state D (1.0 bar) and finally compressed adibatically to A.5 R and it is independent of temperature. (b) Determine the entropy change of surroundings when 100 g benzene vaporizes at its normal boiling point. 40L) → A Representing the above change of states on a P-V diagram.0 bar). PROBLEM 229 An ideal gas has C vm = a + bT –1 –1 –2 where a = 25 JK mol and b = 0.0 bar). determine the net work done. determine the net work done.0 moles of this gas is subjected to a thermodynamic change of state from A (300 K. If 3. PROBLEM 230 One mole of an ideal gas defined by state A (400 K. PROBLEM 232 The entropy of vaporization of benzene is 85 JK –1 mol –1 . PROBLEM 233 The entropy of vaporization of acetone is 85 JK –1 mol –1 . 20 L ) → B (1. (a) Estimate enthalpy of vaporization of acetone at its normal boiling point 56°C. 5. ∆E.0 bar) to B (500 K.03 JK mol –1 . 3. W. PROBLEM 234 With the help of following reduction reactions: TiO 2 ( s) + 2C( s) → Ti( s) + 2CO( g ) …(i) TiO 2 ( s) + C( s) → Ti( s) + CO 2 ( g ) …(ii) .5 R Adiabatic compression Depicting the above change on a P-V diagram.0 bar) is heated at constant pressure to B (500 K) and then cooled at constant volume to C. determine the net work done in this cyclic process. 5. ∆H and ∆S.0 bar) Reversible C → D (3.0 bar. (b) Determine entropy change of surrounding if 100 g of acetone condenses at its boiling point. 1.30 Problems in Chemistry PROBLEM 227 One mole of He(g) is mixed isothermally and reversibly with 2. determine q. Determine ∆S. 2. PROBLEM 228 C vm for an ideal gas is 2. (a) Estimate the enthalpy of vaporization of benzene at its normal boiling point of 80°C.0 mole of Ne(g).0 moles of this gas is subjected to the following change of state : Reversible A (1.5 R . Depicting on a P-V diagram. PROBLEM 239 Consider the thermal decomposition of solid CaCO 3 as: . mole percentage of trans-2-butene at new equilibrium was 18.7. Also. Also. determine which will be the predominant mode of reduction of TiO 2 ( s) at 1000 K. determine standard state entropy change ( ∆S ° ) for the decarboxylation reaction. PROBLEM 236 follows: The thermodynamic informations for isomerization of alkene (C 4 H 8 ) at 300 K are as trans-2-butene cis-2-butene H 3C CH 3 H 3C 1 C==C H H C==C H H ∆G ° = 66 kJ mol –1 f ∆H ° = − 7 kJ mol –1 f CH 3 ∆G ° = 63 kJ mol –1 f ° ∆H = −11. Determine ∆H ° and ∆S ° for the isomerization reactions below: cis-2-butene 2-methylpropene trans-2-butene 2-methylpropene PROBLEM 237 At a temperature above 65 K. given ∆Gf° (CO) = − 200 kJ mol –1 .66 and PCO = 1.e. PROBLEM 235 The reaction for the production of synthetic fuel ‘water gas’ from coal is: C( gr ) + H 2O( g ) → CO( g ) + H 2 ( g ) 2 3 Standard molar entropies of C( gr ). 190 and 131 JK –1 mol –1 respectively. decarboxylation of acetic acid. Determine the standard reaction free energy of reaction at 27°C.31 Problems at 1000 K.. If ∆H f° of CH 3COOH. − 394 and − 74. 70. H 2O( g ). ∆Gf° (CO 2 ) = − 396 kJ mol –1 and ∆G f° TiO 2 ( s) = − 762 kJ mol –1 . PCO2 = 0.2 kJ mol –1 f H CH 3 C==C H CH 3 2-methylpropene ∆G °f = + 58 kJ mol If the temperature of the above system is increased to 400 K and equilibrium was allowed to re-establish. standard enthalpy of formations of H 2O and CO are –242 and –111 kJ mol –1 respectively. What is the driving force for getting this reaction to proceed? PROBLEM 238 For the reaction: H 2 ( g ) + CO 2 ( g ) H 2O( g ) + CO( g ) ∆G at 2000 K is 2540 J.8 kJ/mol respectively. where partial pressures of the species are PH 2 = 0. PH 2O( g ) = 0.78. (i. loss of CO 2 ) becomes spontaneous. Determine equilibrium composition of the gaseous mixture. predict about the spontaneity and effect of temperature on direction of reaction.5. CO( g ) and H 2 ( g ) are 5.25.2 atm respectively. CO 2 ( g ) and CH 4 are −484. In the final state.8 + 0. at 1000 K. calculate the maximum height to which the car can be driven on 2. PROBLEM 247 For chloroform gas C PM is expressed as: C PM = 24.00 atm.32 Problems in Chemistry CaCO 3 ( s) CaO( s) + CO 2 ( g ). initially at 5. .75 L to 3. If C P for each gas is (5 / 2) R. The equilibrium vapour pressure of CO 2 at 700°C and 950°C are 22.00 Lit. is adiabatically expanded against a constant pressure of 5. PROBLEM 240 A certain reaction is spontaneous at 72°C.0 atm pressure is mixed adiabatically with one mole of a different gas at 100°C and 1. (c) The change in volume involves a free expansion. For the gas C v =1. what is the minimum value of ∆S for the reaction? PROBLEM 241 The internal engine of a 1200 kg car is designed to run on octane whose enthalpy of combustion is 5510 kJ/mol.0133 mole of an ideal gas.5 atm and V = 730 mL. Assume the cylinder temperature is 2200°C and the exit temperature is 760°C and ignore all form of friction.3 ln T Determine Gibb’s free energy change ∆G of one mole of nitrogen if it is heated from 298 K to 348 K at 2. PROBLEM 243 A 550 ml sample of an ideal gas at 300 K exerts 3 atm. ∆G and ∆H. PROBLEM 245 One mole of an ideal gas originally at a volume of 8. The mass of 1. at 700 K. determine ∆E . determine ∆S (mixing). P = 3. Calculate ∆S . PROBLEM 246 One mole of an ideal gas at 0°C and 1. expands isothermally and reversibly from 3. C vm = (5 / 2) R .00 L to 10 L. Calculate ∆S .1 + 29.021T JK –1 mol –1 . ∆H and ∆S .0 atm pressure.00 atm. ∆H and ∆E.0 mole of gas from volume 100 L at 500 K to a volume of 70 Lit.8 × 10 −2 T − 9 × 10 −5 T 2 JK –1 mol –1 . W . (b) The expansion takes place against a constant pressure of 3. Calculate values of ∆S for the process when: (a) The expansion takes place reversibly. Calculate ∆H ° and ∆S ° for the reaction. If CV = 18.9 + 14. entropy function as a function of temperature is expressed as: S = 25. determine entropy change involved in heating 2.1 kg. If the car is moving up a slope. Calculate ∆S and ∆E and ∆H.0 atm until equilibrium is attained.0 gallon of the fuel.0 atm to yield a mixture. The thermodynamic state of the system changes in a process.0 L at 298 K. is allowed to expand adiabatically until final volume is 16.5 R .00 Lit.0 gallon of fuel is 3. PROBLEM 244 A sample of 0. PROBLEM 249 One mole of an ideal gas initially at 400 K and 10 atm. PROBLEM 242 One gram sample of oxygen undergoes free expansion from 0.6 and 1830 mm of Hg. PROBLEM 248 For N 2 ( g ). If the enthalpy change for the reaction is 19 kJ. Assuming this gas to be ideal. q. Assuming the volume to be constant. If iron boils at 3133 K and enthalpy of vaporization is 349 JK –1 mol –1 .00 atm and 298 K was connected to a flask containing 1. . determine ∆S system . If the initial pressure was 1.0 atm to 100 atm.Problems 33 PROBLEM 250 Molar volume of C 6 H 6 (l) is 89 c.00 moles of liquid benzene from 1. determine ∆G for compression of 5. PROBLEM 253 One mole of solid iron was vaporized in an oven at 3500 K. at 27°C and 1.c.00 bar and 298 K. Determine the entropy change for the system. PROBLEM 251 One mole of an ideal gas at 25°C is subjected to a reversible isoentropic expansion until final temperature reached to 75°C.0 atm pressure. determine final pressure CV = (3 / 2) R .00 mol of N 2 gas at 2. PROBLEM 252 A flask containing 1.00 mol of N 2 at 4.0 atm. The gases were allowed to mix isothermally. ∆S surroundings and ∆S universe .