Pathi* CHEMISTRY - STOICHIOMETRY - ASSIGNMENT PASSAGES I. 31-08-06 Following experiment is designed to determine calcium content in the blood. Read the experiment and answer the questions at the end of it. Calcium oxalate (CaC2O4) is insoluble in water. For this reason it can be used to determine the amount of Ca2+ ions in fluids such as blood. The calcium oxalate isolated from blood is dissolved in acid and titrated against a standardized KMnO4 solution. In one test it is found that the calcium oxalate isolated from a 10.0 mL sample of blood requires 25 mL of 1 x 10-3 M KMnO4 for titration. Calculate the number of milligrams of calcium per mL of blood. 1) 0.50 2) 10.0 3) 0.25 4) 5.0 Milliequivalents of KMnO4 used were: 1) 0.125 2) 0.025 3) 0.250 4) 0.050 Calcium content expressed in ppm is : 1) 250 2) 200 3) 150 4) 100 Above titration takes place in acidic medium. Acid chosen is : 1) H2SO4 2) HCl 3) CH3COOH 4) HCOOH Indicator in the above titration is : 1) phenolphthalein 2) methylene blue 3) methyl orange 4) KMnO4 (self-indicator) Following titration method is given to determine total content of the species with variable oxidation states. Answer the questions given at the end of it. A quantity of 25.0 mL of solution containing both Fe2+ and Fe3+ ions is titrated with 25.0 mL of 0.0200 M KMnO4 (in dilute H2SO4). As a result, all of the Fe2+ ions are oxidized to Fe3+ ions. Next 25 mL of the original solution is treated with Zn metal. Finally, the solution requires 40.0 mL of the same KMnO4 solution for oxidation to Fe3+. MnO4- + 5Fe2+ + 8H+ ® Mn2+ + 5Fe3+ + 4H2O Molar concentration of Fe2+ in the original solution is : 1) 0.01 M 2) 0.02 M 3) 0.10 M 4) 0.20 M Molar concentration of Fe3+ in the original solution is : 1) 0.06 M 2) 0.16 M 3) 0.032 M 4) 0.012 M Zinc added in the second titration will 1) oxidize Fe2+ to Fe3+ 2) reduce Fe3+ to Fe2+ 3) reduce Fe3+ to Fe 4) reduce Fe2+ to Fe If 0.02 M K2Cr2O7 is used instead of 0.02 M KMnO4, its volume required in these titrations are respectively: 1) 25 mL, 40 mL 2) 25 mL, 15 mL 3) 20.8 mL, 33.3 mL 4) 10.4 mL, 16.7 mL Read the following experimental facts and answer the questions at the end of it. “KMnO4 and K2Cr2O7 are widely used volumetric reagents for analytical estimation of iron, hydrogen peroxide, iodide, ozone, sulphite, nitrite, etc. Reaction is carried out in acidic medium.” Equivalents of MnO4- and Cr2O72- per mol of the ion in acidic medium are in the ratio of : 1) 1 : 1 2) 1 : 5 3) 6 : 1 4) 5 : 6 1 mol of ferrous oxalate will require x mol of KMnO4 in acidic medium. x is : 1) 0.6 2) 0.8 3) 9.0 4) 1.2 1 mol of Cr2O72- will oxidize y mol of ferric oxalate. y is ….. 1) 1 2) 2 3) 3 4) 4 1 mol of ferrous sulphate is oxidized by x mol of MnO4- and y mol of Cr2O72- . x and y are in the ratio of : 1. 2. 3. 4. 5. II. 1. 2. 3. 4. III. 1. 2. 3. 4. Pathi * IV. 31-08-06 1) 5 : 6 2) 6 : 5 3) 3 : 2 4) 2 : 3 Questions given below are based on the following stoichiometric equation. Cisplatin, an anticancer agent used for the treatment of solid tumors, is prepared by the reaction of ammonia with potassium tetra-chloroplatinate: K2PtCl4 + 2NH3 ® [Pt(NH3)2]Cl2 + 2KCl Potassium cisplatin Tetrachloroplatinate Assume that 10.0 g of K2PtCl4 and 10 g of NH3 are allowed to react. (K = 39, Pt = 195, Cl = 35.5) Which reactant is limiting an which is in excess? Limiting Excess (1) K2PtCl4 NH3 (2) NH3 K2PtCl4 (3) exact molar ratio (4) would be decided by the quantity of the product formed Number of mol of K2PtCl4 consumed is : 1) 0.48 2) 0.024 3) 0.012 Number of mol of NH3 consumed is: 1) 0.048 2) 0.024 3) 0.096 Number of mol of cisplatin formed is : 1) 0.012 2) 0.024 3) 0.048 Number of mol of excess reactant which remains unreacted is : 1) 0.024 2) 0.34 mol 3) 0.54 mol 1. 2. 3. 4. 5. 4) 0.096 4) 0.192 4) 0.192 4) 0.56 mol V. Questions given below are based on following sequence of the reactions: Phosphoric acid, H3PO4, is widely used to make fertilizers, and can be prepared in a two-step process. Step I : P4 + 5O2 ® P4O10 Step II : P4O10 + 6H2O ® 4H3PO4 We allow 310 grams of phosphorus to react with excess oxygen, which forms tetraphosphorus decoxide, P4O10, in 50% yield. In the step II reaction, 25% yield of H3PO4 is obtained. (P = 31, H = 1, O = 16) Assume 100% yield then number of mol of H3PO4 would be obtained : 1) 1.25 mol 2) 10.0 mol 3) 5.0 mol 4) 2.5 mol Actual number of mol of H3PO4 obtained based on experimental conditions is: 1) 5.0 mol 2) 2.5 mol 3) 1.25 mol 4) 0.3125 mol H3PO4 thus formed is converted into calcium phosphate by treating with 1 mol of calcium hydroxide. Calcium phosphate obtained is : 1) 2.5 mol 2) 0.33 mol 3) 0.1563 mol 4) 1.25 mol Following short write-up describes synthesis of I2 from natural source chile salt peter. Answer the questions at the end of it. Chile salt peter is a natural source of NaNO3 which also contains NaIO3. The NaIO3 can be used as a source of iodine produced in the following reactions. IO3- + 3HSO3- ® I- + 3H+ + 3SO425I- + IO3- + 6H+ ® 3I2(s) + 3H2O 1.0 L of the starting solution which contains 5.80 g NaIO3/L, is treated with stoichiometric quantity of 1. 2. 3. VI. 1. 2. 3. 4. 31-08-06 NaHSO3. Then a further quantity of the starting solution is added to the reaction mixture to bring about the second reaction. [I = 127, Na = 23, S = 32] How many grams of NaHSO3 are required in step (i) ? 1) 5.80 g 2) 17.4 g 3) 9.14 g 4) 3.0 g What additional volume of the starting solution must be added in step (ii)? 1) 0.2 L 2) 0.4 L 3) 0.8 L 4) 1.0 L How many equivalents of IO3 are present in one mole of NaIO3 in step (i) 1) 2 2) 4 3) 6 4) 8 How many equivalents of IO3- are used in step (ii) 1) 6 2) 0.029 3) 0.06 4) 0.035 Following experiment is given to determine the oxidation state of vanadium at different stages. When ammonium vanadate is heated with oxalic acid solution, a compound Z is formed. A sample of Z was titrated with KMnO4 solution is hot acidic solution. The resulting liquid was reduced with SO2, the excess SO2 is boiled off and the liquid again titrated in the KMnO4. The ratio of the volumes of KMnO4 used in them two titrations was 5 : 1. KMnO4 oxidises all oxidation state of vanadium to vanadium (+V) and SO2 reduces vanadium (+V) to vanadium (+IV). Read the above experiment and answer the following questions. What is the oxidation state of vanadium in the compound Z 1) +2 2) +1 3) 0 4) -1 If vanadium exists as VO43-, reduced species by SO2 would be : 1) VO422) VO323) VO224) VO2Consider following redox reaction: VO32- + MnO4- ® Mn2+ + VO431 mol of VO32- is oxidized by x mol of MnO4- . Thus, x is : 1) 0.2 2) 0.4 3) 0.8 4) 1.0 Number of mol of MnO4- required to titrate 1 mol of Z in hot acidic solution is : 1) 0.2 2) 0.4 3) 0.8 4) 1.0 Thus compound Z is : 1) VO432) VO323) V (vanadium) 4) VO22+ Pathi * VII. 1. 2. 3. 4. 5. VIII . Following experiment is being used to remove chromium metal from polluted water. The chromate ion may be present in waste water from a chrome plating plant. It is reduced to insoluble chromium hydroxide, Cr(OH)3 by dithionite ion, S2O42- in basic solution. 3S2O42- + 2CrO42- + 2H2O + 2OH- ® 6SO32- + 2Cr(OH)3 100 L of water require 387 g of Na2S2O4. (Cr = 52, S = 32, O = 16) Read the above technique and answer the following questions. 1. 2. 3. Presence of CrO42- in waste water is detected by : 1) Pb2+ 2) Ba2+ 3) both 4) none If waste water is also found to contain some Cr2O72- then its conversion to CrO42- can be done: 1) by passing CO2 2) by adding Na2CO3 3) by heating 4) by adding Fe2+ 2If CO2 is passed into waste water containing CrO4 (yellow) then: 1) solution turns green due to formation of Cr3+ 2) solution turns blue due to formation of CrO5 3) solution turns orange due to formation of Cr2O724) no effect takes place 4. 5. 6. 7. 8. Number of mol of CrO4 present in 100 L waste water is 1) 2.224 mol 2) 1.483 mol 3) 1.112 mol 4) 4.448 mol Molarity of CrO42- solution is 1) 0.02224 M 2) 0.01483 M 3) 0.01112 M 4) 0.0448 M Concentration in ppm of Na2CrO4 is 1) 2.4 x 103 ppm 2) 1.2 x 103 ppm 3) 4.8 x 103 ppm 4) 1.0 x 103 ppm 2Number of equivalents of S2O4 required for the above treatment is 1) 2.224 2) 1.483 3) 4.448 4) 2.966 Completion stage is indicated by 1) formation of green precipitate of Cr(OH)3 2) BaCl2 which gives no precipitate at the end 3) both (a) and (b) 4) none of these Read the following analytical report and answer the questions at the end of it. Calcium lactate is used in the food and beverage industries. It has also been used medicinally for treatment of various allergies, for treatment of muscular leg cramps, and as an antidote for a variety of poisons, including lead, arsenicals and carbon tetrachloride. A 0.8274 g sample of anhydrous calcium lactate is found by analysis to contain 0.2732 g of C, 0.0382 g H, 0.1520 g Ca and 0.3640 g O. Each mol of calcium lactate is found to contain one mole of calcium ions. Calcium lactate can be crystallized from water as pentahydrate salt. Simplest formula of the calcium lactate is 1) CaO6C6H10 2) CaO3C3H5 3) CaO2C3H3 4) CaO2C3H5 Formula weight of calcium lactate is : 1) 129 g mol-1 2) 111 g mol-1 3) 218 g mol-1 4) 113 g mol-1 How many grams of calcium lactate pentahydrate would be recovered from 1 g of anhydrous salt? 1) 1.41 g 2) 1.00 g 3) 1.27 g 4) 1.51 g Select correct statement(s) about lactic acid: P, Br2 Ag 2 O/H 2 O 1) it has a stereocentre 2) it can be synthesized from propanoic acid ¾¾¾ ® ¾¾¾¾ ® 3) it is stronger than propanoic acid 4) all of the above statements are correct Following passage is for the drunken drivers on roads which are becoming fatal by their wrong driving. Every year in our country about 25,000 people are killed and 500, 000 more are injured as a result of drunk driving. In spite of efforts to educate the public about the dangers of driving while intoxicated and stiffer penalties for drunk driving offenses, law enforcement agencies still have to devote a great deal of work to remove drunk drivers from roads. The police often use a device called a breath analyzer to test drivers suspected to being drunk. The chemical basis of this device is a redox reaction. A sample of the driver’s breath is drawn into the breath analyzer, where it is treated with an acidic solution of potassium dichromate. 3CH3CH2OH + 2K2Cr2O7 + 8H2SO4 ® 3CH3COOH + 2Cr2(SO4)3 + 2K2SO4 + 11H2O The driver’s blood alcohol level can be determined readily by measuring the degree of this colour change (read from a calibrated meter on the instrument.) The current legal limit of blood alcohol content is 0.1 percent by mass. Anything higher constitutes intoxication. Read the passage and answer the questions given below: 2- Pathi * 31-08-06 IX 1. 2. 3. 4. X. 1. 2. Above test is based on : 1) smell of ethanol and ethanoic acid 3) change of colour orange to green Equivalent mass of K2Cr2O7 is 2) change of colour yellow to blue 4) change of colour orange to colourles Pathi * 1) 3. 31-08-06 4. molar mass molar mass molar mass molar mass 2) 3) 4) 6 3 2 1 Equivalent mass of CH3CH2OH is : molar mass molar mass molar mass molar mass 1) 2) 3) 4) 1 2 3 4 The alcohol content in a 10.0 g sample of blood from a driver required 4.23 mL of 0.07654 M K2Cr2O7 for titration. Should the police prosecute the individual for drunken driving? 1) yes 2) no 3) nothing can be predicted PART – B 1. 2.68 gm of a mixture of CaCO3, MgCO3 and NaHCO3 suffered a loss of 1.19 gm of heating. The residue on treatment with excess of hydrochloric acid gave 0.112 lit of CO2 as measured at S.T.P. Calculate the weight of each component. [Ans : CaCO3 = 1g, MgCO3 = 0.84 g] A 1.00g sample of KClO3 was heated under such conditions that a part of it decomposed according to the equation (i) 2KClO3 ® 2KCl + 3O2 and the remaining underwent change according to the chemical reaction 4KClO3 ® 3KClO4 + KCl. If the amount of oxygen evolved was 146.8 ml at S.T.P. Calculate the percentage by weight of KClO4 in the residue. [O = 16, Cl = 35.5, K = 39.1] [Ans : 49.83% Steam is passed over hot magnesium to generate hydrogen. Calculate the Wt. of magnesium required to produce just sufficient hydrogen to combine with all the oxygen obtained by complete decomposition of 98g of KClO3 of 50% purity. 50ml of CO at NTP were mixed with 300ml of air (21% of O2 by volume) at 270C and 760mm pressure and the mixture is exploded. Calculate the volume of the residual gases at 270C and 700mm pressure. [Ans: 355.5ml] A flash bulb used for taking photograph in poor light contains 30ml of oxygen at a pressure of 780mm at 270C. Supposing that the metal wiere flashed is pure aluminium which is oxidized to aluminium oxide in the process of flashing. Calculate the minimum weight of aluminium wire that is to be used for maximum efficiency. [O=16, Al=27] [Ans: 0.045] 10ml of a solution of hydrogen peroxide labeled, 10 volume, just decolorizes 100ml of potassium permanganate solution acidified with dilute sulphuric acid. Calculate the amount of KMnO4 in the given solution. [Ans: 0.5648g] In the analysis of a 0.600g sample of feldspar, a mixture of the chlorides of sodium and potassium is obtained, which is 0.1180g. Subsequent treatment of the mixed chloride with silver nitrate gives 0.2451g of silver chloride. What is the percentage of sodium oxide and potassium oxide in feldspar? [O=16, Na=23, Cl=35, K=39.1, Ag=108] [Ans: Na2O=3.58%, K2O=10.63%] 2. 3. 4. 5. 6. 7. 8. Dichromate ion in acid solution oxidizes stannous ion as 3Sn +2 +14H + +Cr2 O 7 -2 ® 3Sn +4 +2Cr +3 +7H 2 O (a) If SnCl2 is the source of Sn+2, how many g of SnCl2 would be contained in 2 litre of 0.1 N solution? Pathi * (b) 31-08-06 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. [Ans: 18.97g] If K2Cr2O7 is the source of Cr2O7-2, what is the normality of solution containing 4.9g K2Cr2O7 in 0.1 litre of solution. [Ans: 1 N] Metallic tin in the presence of HCl is oxidized by K2Cr2O7 to stannic chloride. What volume of decinormal dichromate solution would be reduced by 1g of tin? [Ans: V=336.98ml] The equivalent weight of an element is 13.16. It forms an acidic oxide which with KOH forms a salt, isomorphous with K2SO4. Deduce at wt. of element. [Ans: 78.96] 1g of H2O2 solution containing X% H2O2 by weight requires X ml of KMnO4 for complete oxidation in acid medium. Calculate normality of KMnO4 solution. [Ans:0.588] 1.2g of commercial sample of oxalic acid was dissolved in 200ml of water. 10ml of this sample required 8.5ml of N/10 KMnO4. Calculate % of purity of sample. [Ans: 89.25%] 0.56g of lime stone was treated with oxalic acid to give CaC2O4. The precipitate decolorized 45ml of 0.2N KMnO4 in acid medium. Calculate % of CaO in lime stone. [Ans: 45%] 5.7g of bleaching powder was suspened into 500ml of water. 25ml of this suspension on treatment with KI and HCl liberated iodine which reacted with 24.35ml of N/10 Na2S2O3. Calculate % of available Cl2 in bleaching powder. [Ans: 30.33%] Mixture contains NaCl and an unknown chloride MCl 1gm of this is dissolved in water. Excess of acidified AgNO3 solution is added to it 2.567gm of a white precipitate is 1gm of the original mixture is heated to 3000C. Some vapours comes out which are absorbed in acidified AgNO3 solution. 1.341gm of a white precipitate is obtained. Find the molecular weight of unknown chloride. A solution of 0.2g of a compound containing Cu+2 and C2O4-2 ions of titration with 0.02M KMnO4 in presence of H2SO4 consumes 22.6ml oxidation. The resulting solution is neutralized by Na2CO3, acidified with dilute CH3COOH and titrated with excess of KI. The liberated I2 required 11.3ml of 0.05M Na2S2O3 for complete reduction. Find out mole ratio of Cu+2 and C2O4-2 in compound. [Ans: 1/2 ] 2.6g sample of pyrolusite was boiled with 65ml of N oxalic acid and excess of dil. H2SO4. The liquid was then filtered and the residue washed. The filtrate and washing were mixed and made upto 500ml. 100ml of this solution required 50ml of N/10 KMnO4. Calculate % of MnO2 in sample. [Ans: 66.92%] Calculate the weight of MnO2 and the volume of HCl of specific gravity 1.2g ml-1 and 4% nature by weight, needed to produce 1.78 litre of Cl2 at STP by the reaction MnO2+4HCl→MnCl2+2H2O+Cl2 [Ans: 6.9134g] A mixture of H2C2O4 (Oxalic acid) and NaHC2O4 weighing 2.02g was dissolved in water and the solution made up to one litre. Ten milli litres of the solution required 3.0ml of 0.1N sodium hydroxide solution for complete neutralization. In another experiment 10.0ml of the same solution, in hot dilute sulphuric acid medium, required 4.0ml of 0.1N KMnO4 solution. For complete reaction. Calculate the masses of H2C2O4 and NaHC2O4 in the mixture. [Ans: 0.9g, 1.12g] A 1.0g sample of Fe2O3 solid of 55.2% purity is dissolved in acid and reduced by heating the solution with zinc dust. The resultant solution is cooled and made up to 100.0ml. An aliquot of 25.0ml of this solution requires 17.0ml of 0.0167M solution of an oxidant for titration. Calculate the number of electrons taken up by the oxidant in the reaction of the above titration. Pathi * 21. 31-08-06 22. 23. 24. 25. [Ans: 6] A 8.0g sample contained Fe3O4, Fe2O3 and inert materials. It was treated with an excess of aqueous KI solution in acidic medium, which reduced all the iron to Fe2+ ions. The resulting solution was diluted to 50.0 cm3 and a 10.0 cm3 of it was taken. The liberated iodine in this solution required 7.2 cm3 of 1.0M Na2S2O3 for reduction to iodide. The iodine from another 25.0 cm3 sample was extracted, after which the Fe2+ ions was titrated against 1.0M KMnO4 in acidic medium. The volume of KMnO4 solution used was found to be 4.2cm3. Calculate the mass percentages of Fe3O4 and of Fe2O3 in the original mixture. (Given, molar mass of Fe=56g mol-1) [Ans: 17.4, 24.0] What are the masses of P4O6 and P4O10 that will be produced by the combustion of 2.0g of P4 in 2.0g of oxygen leaving no P4 and O2. [Ans: 1.996g, 2.004g] A precipitate of Ag Brand AgCNS weighing 1.002g was dissolved in 60.0 cm3 of 0.25M KCN solution. The excess cyanide required 1.7cm3 of 0.1M AgNO3 for titration to the turbid end point. Calculate the percentage of AgCNS in the original precipitate [Ans: 70.2%] 1.5g pyrolusite ore was treated with 10g of Mohr’s salt and dilute sulphuric acid resulting into the following equation MnO2+2Fe2++4H+→Mn2++2Fe3++2H2O. After the reaction is over, the solution was made up to 250ml. When 50ml of this solution was titrated against N/10 K2Cr2O7 solution. The volume of the latter consumed was found to be 10ml. Calculate the percentage of MnO2 in the given pyrolusite sample. [Ans: 59.4] 0.5g sample of iron containing mineral mainly in the form of CuFeS2 was reduced suitably to convert all the ferric ions into ferrous ions ( Fe+3 ® Fe +2 ) and was obtained as solution. In the absence of any interfering radical, the solution required 42ml of 0.01M K2Cr2O7 for titration. Calculate % of CuFeS2 in sample. [Ans: 92.48%] A sample of ferrous sulphate and ferrous oxalate was dissolved in dil.H2SO4. The complete oxidation of reaction mixture required 40ml of N/15 KMnO4. After the oxidation the reaction mixture was reduced by Zn and H2SO4. On again oxidation by same KMnO4, 25ml were required. Calculate the ratio of Fe in ferrous sulphate and oxalate. [Ans: 2.3] Hydroxylamine reduces iron III according to the equation 4Fe+32NH2OH→N2O+H2O+4Fe+2+4H+. Iron II thus produced is estimated by titration with standard KMnO4 solution. The reaction is MnO 4- +5Fe+2+8H+→Mn+2+5Fe+3+4H2O. A 10ml of hydroxylamine solution was diluted to one litre. 50ml of this diluted solution was boiled with an excess of Fe+3 solution. The resulting solution required 12ml of 0.02M KMnO4 solution for complete oxidation of Fe+2. Calculate the weight of NH2OH in one litre of original solution. [Ans: 39.6 g/litre] A polyvalent metal weighing 0.1g and having atomic weight 51.0 reacted with dil.H2SO4 to give 43.9ml of H2 at STP. The solution containing the metal in the lower oxidation state was found to require 58.8ml of 0.1N KMnO4 for complete oxidation. What are valencies of metal? [Ans: 2 and 5] 26. 27. 28. 29. The calcium contained in a solution of 1.048g of a substance being analysed was precipitated with 25ml H2C2O4. The excess of C 2 O -2 4 in one fourth of filtrate was back titrated with 5ml of 0.1025N KMnO4. To determine the conc. of H2C2O4 solution, it was diluted four folds and titration of 25ml of dilute solution used up 24.1ml of same KMnO4 solution. Calculate % of Ca in substance. Pathi * 30. 31-08-06 31. 32. [Ans: 14.95%] (a) CuSO4 reacts with KI in acidic medium ti liberate I2. 2CuSO4+4KI→Cu2I22K2SO4+I2 (b) Mercuric per iodate Hg5(IO6)2 reacts with a mixture of KI and HCl following the equation. Hg5(IO6)2+34KI+24HCl → 5K2HgI4+8I2+24KCl+12H2O (c) The liberated iodine is titrated against Na2S2O3 solution one ml of which is equivalent to 0.0499g of CuSO4.5H2O. What volume in ml of Na2S2O3 solution will be required to react with I2 liberated from 0.7245g of Hg5(IO6)2. M.Wt. of Hg5(IO6)2 = 1448.5 and M.Wt. of CuSO4.5H2O = 249.5. [Ans: 40 ml] A sample weighing 2.180g containing a mixture of AO and A2O3 takes 0.015 mole of K2Cr2O7 to oxidize the sample completely to form AO 4- and Cr+3. If 0.0187 mole of AO 4- is formed. What is at.wt. of A? [Ans: 99] -2 Calculate the amount of SeO3 in solution on the basis of following data. 20ml of M/60 solution of -2 KBrO3 was added to a definite volume of SeO3 solution. The bromine evolved was removed by boiling and excess of KBrO3 was back titrated with 5.1ml of M/25 solution of NaAsO2. The reactions are given below -2 + (1) SeO3 (2) BrO3- +AsO 2- +H 2 O ® Br - +AsO-3 +BrO3 +H + ® SeO-2 4 +Br2 +H 2 O 4 +H A mixture containing As2O3 and As2O5 required 20.10ml of 0.05N iodine for titration. The resulting solution is then acidified and excess of KI was added. The liberated iodine required 1.1113g hypo (Na2S2O3 5H2O) for complete reaction. Calculate mass of mixture. The reactions are (1) As 2O3 +2I2 +2H 2O ® As 2O5 + 4H + + 4I - (2) As 2O5 +4H + + 4I - ® As 2O3 + 2I 2 + 2H 2 O [Ans: 0.2497g] 1.5g of brass containing Cu and Zn reacts with 3M HNO3 solution the following reactions take place. +2 Cu+HNO3 → Cu+2+NO2(g)+H2O Zn+H++ NO3- → NH + 4 +Zn +H2O The liberated NO2(g) was found to be 1.04 litre at 250C and one atm. (a) Calculate the percentage composition of brass. (b) How many ml of 3M HNO3 will be required for completely reacting 1g of brass. [Ans: 0.15g, 90%, 10%, 9.558ml] A mixture weighing 4.08g of BaO and unknown carbonate XCO3 was heated strongly. The residue weighed 3.64g. This was dissolved in 100ml of 1N HCl. The excess acid required 16ml of 2.5N NaOH solution for complete neutralization. Identify the metal M. [Ans: Ca] (a) What is the mass of sodium bromate and molarity of solution necessary to prepare 85.5ml of 0.672N solution when the half-cell reaction is BrO3- +6H++6e-→Br -+3H2O. [Ans: 1.446 g] (b) What would be the mass as well as molarity if the half cell reaction is 2BrO3- +12H++10e-→Br2+6H2O [Ans: 1.735g] 33. 34. 35. 36. 37. Only gaseous remain after 15gm carbon (Red hot) is treated with air originally occupying 25.8 lit at 270C and 5 atm pressure. The gaseous mixture is evolved cooled and then passed through 2 lit. of 1M NaOH. The resulting solution was titrated with 1.5M HCl solution using phenopthalein as indicator. 38. 31-08-06 Calculate the volume of HCl solution needed to arrive at the equivalence point. Air contains 79% N2, 20% O2 and 1% CO2 by volume. One gm of a metal ion MX+ (AW=100) was treated with 3.34gm hydrazine mono hydrate N2H4.H2O (90% pure) and CO2 gas was passed through the mixture when entire metal got precipitated as a complex of formula (N2H5)m é ë M ( N 2 H 3COO )n ù û . One tenth of the volume of the titrate after filtering of the precipitate, required 20ml of 0.1M KIO3 solution in 6M HCl. For the following reaction. IO3- + N 2 H 4 + 2H + + 2Cl - ® ICl+3H 2O+N 2 The solid complex was heated to affect complete decarboxylation and mixture of gaseous evolved was passed through KOH solution when up on its weight increased by 1.32gm. Find m, n, x. [Ans: m+n=4] Pure Na2C2O4 and KHC2O4. H2C2O4 are mixed in such a proportion that each gram of the mixture reacts separately with equal volumes of 0.1M KMnO4 and 0.1M NaOH. What is the proportion? [Ans: 3.38/1] Pathi * 39. 40. 41. 42. 43. 44. 45. 46. 47. A mixture of FeO and Fe3O4 when heated in air to a constant mass gains 5 percent in its mass. Find the composition of the initial mixture. [Ans: 20.12 mass of % FeO and 79.88 mass % Fe3O4] A sample containing amino acid alanine, CH3CH(NH2)COOH plus inert matter is analyzed by the Kjeldahl method. A 2.00g sample is digested, the NH3 is distilled and collected in 50.0ml of 0.150M H2SO4, and a volume of 9.0ml of 0.100M NaOh is required for back titration. Calculate the percent alanine in the sample. [Ans: 62.8] The elemental Se, dispersed in a 5.0ml sample of detergent for dandruff control, was determined by suspending the sample in a warm, ammonical solution that contained 45.0ml of 0.020M AgNO3, 6Ag++3Se(s)+6NH3+3H2O→2Ag2Se(s)+Ag2SeO3(s)+ 6NH + The mixture was next treated with 4 . excess nitric acid which dissolved the Ag2SeO3 and the excess AgNO3 consumed 16.74ml of 0.0137 N KSCN in a Volhard titration. How many milligrams of Se were contained per milliliter of sample? [Ans: 7.94 mg/ml] A precipitate of AgCl and AgBr weighs 0.4066g. On heating in a current of chloring, the AgBr is converted to AgCl and the mixture loses 0.0725g in weight. Find the % of Cl - in original mixture. [Ans: 6.13%] A sample of clay was partially dried and then contained 50% silica and 7% water. The original clay contained 12% water. Find the % of silica in original sample. [Ans: a=47.31] A solution contains Na2CO3 and NaHCO3. 10ml of this requires 2.0ml of 0.1M H2SO4 for neutralization using phenolphthalein as indicator. Methyl orange is then added when a further 2.5ml of 0.2M H2SO4 was required. Calculate the strength of Na2CO3 and NaHCO3 in solution. [Ans: Strength of Na2CO3 = 4.24g litre-1, NaHCO3 = 5.04g litre-1] Hydrogen peroxide solution (20ml) reacts quantitatively with a solution of KMnO4 (20 ml) acidified with dilute H2SO4. The same volume of KMnO4 solution is just decolourised by 10ml of MnSO4 in neutral medium simultaneously forming a dark brown precipitate of hydrated MnO2. The braun precipitate is dissolved in 10ml of 0.2M sodium oxalate under boiling condition in the presence of dilute H2SO4. Calculate molarities of H2O2. [Ans: 0.1 M] A fused mixture of rubidium fluoride and uranium (IV) fluoride can be oxidized with fluorine to produce a uranium compound in which the uranium is mainly but not entirely in the +5 oxidation states. The product is found to contact 54.93% uranium. A 1.0357gm sample of the product immersed in 100ml of 10.07 centimolar acidified potassium iodide solution reaction accordingly as following Pathi * - 31-08-06 48. 49. 50. 51. 52. 53. equation. 2l +2UF6 ¾¾ ® 2UF4 + I 2 + 4F . The iodine produced was titrated with 14.80ml of 14.94 centimolar sodium thiosulphate solution. What % of the original mixture oxidized to +5 oxidation state? [Ans: 93.3%] A sample of Magnesium was burnt in air to give a mixture of MgO and Mg3N2. The ash was dissolved in 60 meq of HCl and the resulting solution back titrated with NaOH. 12 meq. Of NaOH were required to react the end point. An excess of NaOH was then added and the solution distilled. The ammonia released was then trapped in 10 meq of second acid solution. Back titration of this solution required 6 meq. Of the base. Calculate the percentage of magnesium burnt to the nitride. [Ans: 27.27%] 1.143g of ferrous oxalate was dissolved in dil.H2SO4 and made up to 100ml. 20 ml of the solution required 38% of N/10 KMnO4 for complete oxidation. On reducing the resulting solution with SO2 and boiling off the excess of SO2. 12.7ml of N/10 were required for re-oxidation. Deduce the formula of the ferrous oxalate in the form Fex(C2O4)yZH2O. [Ans: 180, FeC2O4, 2H2O] The H2S and SO2 concentrations of a gas were determined by passage through three absorber solutions connected in series. The first contained an ammoniacal solution of Cd2+ to trap the sulphide as CdS. The second contained 10.0ml of 0.0396N l2 to oxidize SO2 to SO42 -. The third contained 10.0ml 0.0345 N thiosulphate solution to retain any l2 carried over from the second absorber. A 25.0 litre gas sample was passed through the apparatus followed by an additional amount of pure N2 to sweep the last traces of SO2 from the first and second absorber. The solution from the first absorber was mae acidic and 20.0ml of the 0.0396 N l2 were added. The excess l2 was back titrated with 7.45ml of the thiosulphate solution. The solutions in the second and third absorbers were combined and the resultant iodine was titrated with 1.44ml of the thiosulphate solution. Calculate the concentrations of SO2 and H2S in mg/L of the sample [Ans: 1.689×10-3 mg/lit] 2g of a chromite ore sample was mixed with enough potassium carbonate and potassium chlorate and fused. The reaction that occurred was: 6FeCr2O4+12K2CO3+7KClO3→Fe2O3+12K2CrO4+7KCl+12CO2 The fused mass was cooled and extracted with 2N sulphuric acid. This was filtered and thoroughly washed. The filtrate and washings were collected in a 500ml volumetric flask. When all the soluble portion of the fused mass was extracted, 100ml of 1M solution of ferrous ammonium sulphate were added and the solution made to 500ml. An aliquot of 25ml was titrated with potassium dichromate solution, prepared by dissolving 0.98g of dried potassium dichromate in distilled water in a 250ml volumetric flask. The titration required 32.5ml of this solution. Calculate the percentage of chromium in the sample of the ore. [Ans: 41.6%] A 1.65g sample of FeS2 was oxidized by excess oxygen and the products were SO2 and Fe2+. The SO2 gas produced was passed through an acidified solution of 40ml Barium permanganate produced SO 2 4 and Mn2+. The excess of barium permanganate was diluted to 100ml and 10ml of its was treated with 2excess Kl and the iodine produced required 0.05M, 5ml Na2S2O3 solution producing S4 O 6 . In a separate titration the 25ml same solution of Barium permanganate under alkaline conditions when 2treated with Kl produced l2 that required 20ml of 0.05M Na2S2O3 solution producing S4O6 and Mn6+. Calculate the % of FeS2 in the sample. [Ans: 10%] A 2.5g sample containing As2O5, Na2HAsO3 and inert substance is dissolved in water and the pH is adjusted to neutral with excess NaHCO3. The solution is titrated with 0.15M l2 solution, requiring 11.3ml to just reach the end point, then the solution is acidified with HCl, Kl is added and the liberated l2 requires 41.2ml, 0.015M Na2S2O3 under basic conditions where it converts to SO42 -. Calculate % composition of the mixture. Pathi * [Ans: 3.57%] 31-08-06 PART – C 1. 4.50g of magnesium carbonate were added to double its weight of dilute sulphuric acid. After the reaction was over, it was found that 0.30 gram of magnesium carbonate remained. Calculate the percentage strength of sulphuric acid and volume of carbon dioxide formed at 270C and 760mm pressure. [Mg=24, C=12, O=16, S=32, H=1] [Ans: 1230.7ml] A mixture of aluminium and zinc weighing 1.67gm was completely dissolved in acid and the evolved 1.69 litres of hydrogen gas was measured at 273K and one atmospheric pressure. What was the weight of a aluminium in the original mixture? [Ans: 1.229g] A gas mixture of 3.0 litres of propane and butane on complete combustion at 250C produced 10 litres of CO2. Find out the composition of the gas mixture. [Ans: 33.33%] A gaseous compound of carbon and nitrogen containing 53.8% by weight of nitrogen was found to have a vapour density of 25.8. What is the molecular formula of the compound. (At. Wt. C=12, N=14) [Ans: C2N2] What weight of pyrolusite containing 89.21% of MnO2 will oxidize the same amount of oxalic acid as 37.12ml of permanganate solution of which 1.00ml will liberate 0.0175g of I2 from KI? [Ans: 0.2497g] 20ml of 0.2M MnSO4 are completely oxidized by 16ml of KMnO4 of unknown normality, each forming Mn+4 oxidation state. Find out the normality and molarity of KMnO4 solution. [Ans: 0.167] 0.5g sample containing MnO2 is treated with HCl, liberating Cl2. The Cl2 is passed into a solution of KI and 30.0cm3 of 0.1M Na2S2O3 are required to titrate the liberated iodine, calculate the percentage of MnO2 in sample. [At. Wt. of Mn=55] [Ans: 26.1%] Find out the % of oxalate ion in given sample of oxalate salt of which 0.3g dissolved in 100ml of water required 90ml of N/20. KMnO4 for complete oxidation. [Ans: 66%] 25g of a sample of FeSO4 was dissolved in water containing dil.H2SO4 and the volume made upto 1 litre. 25ml of this solution required 20ml of N/10 KMnO4 for complete oxidation. Calculate % of FeSO4. 7H2O in given sample. [Ans: 88.96%] -2 A solution of 0.1M KMnO4 is used for the reaction S2 O3 +2MnO 4- + H 2 O ® MnO2 + SO-2 4 + OH . What volume of solution in ml will be required to react with 0.158g of Na2S2O3. [Ans: 26.67 ml] 1.6g of pyrolusite ore was treated with 50cm3 of 1.0N oxalic acid and some sulphuric acid. The oxalic acid left undercomposed was raised to 250cm3 in a flask. 25cm3 of this solution when titrated with 0.1N KMnO4 required 32cm3 of the solution. Find out the percentage of pure MnO2 in the sample and also the percentage of available oxygen. [Ans: 48.88%, 18] 25ml of a solution containing Fe+2 and Fe+3 sulphate acidified with H2SO4 is reduced by 3g of metallic zinc. The solution required 34.25ml of N/10 solution of K2Cr2O7 for oxidation. Before reduction with Zinc, 25 ml of the same solution required 22.45 ml of same K2Cr2O7 solution. Calculate the strength of FeSO4 and Fe2(SO4)3 in solution. [Ans : 13.64 g/litre, 9.45 g/litre] 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 31-08-06 A granulated sample of aircraft alloy (Al, Mg, Cu) weighing 8.72 gm was first treated with alkali and then with very dil. HCl leaking a residue. The residue after alkali boiling weighed 2.10 gm and the acid insoluble residue weighed 0.69 gm what is the composition of the alloy. [Ans : Al = 75.9 %, Mg = 16.2 %, Cu = 7.9%] A 50.0 cm3 portion of a mixture of H2SO4 and H2C2O4 required 48.9 cm3 of 0.15 M NaOH solution for titration. Another 50 cm3 required 38.9 cm3 of 0.10 N KMnO4 solution for titration. Calculate the masses of H2SO4 and H2C2O4 present per dm3 of the solution. [Ans : 3.376 g, 3.501 g] One gram of a moist sample of a mixture of KClO3 and KCl was dissolved in water and made up to 250 ml, 25 ml of this solution was treated with SO2 to reduce chlorate into chloride and the excess SO2 was boiled off. When the total chloride was precipitated, 0.1435 g of AgCl was obtained. In another experiment 25 ml of the original solution was heated with 30 ml of 0.2 N solution of FeSO4 and unreacted FeSO4 required 37.5 ml of 0.08 N solution of an oxidizing agent for complete oxidation. Calculate the molar ratio of chlorate and chloride in the given mixture. Fe2+ reacts with ClO3- according to the equation ClO3- + 6Fe2+ + 6H+ ® Cl- + 6Fe3+ + 3H2O. Also calculated the mass percent of moisture present in the moist sample. [Ans : 1.5] 0.2828g of iron wire was dissolved in excess dilute H2SO4 and the solution was made up to 100 ml. 20 ml of this solution required 30 ml of N/30 K2Cr2O7 solution for exact oxidation. Calculate % purity of Fe in wire. [Ans : 99.0%] The reaction Cl2(g) + S2O3-2 ® SO4-2 + Cl- is to be carried out in basic medium. Starting with 0.15 mole of Cl2, 0.010 mole S2O3-2 and 0.30 mole of OH-, how many mole of OH- will be left in solution after the reaction is complete. Assume no other reaction occurs. [Ans : 0.2 mole] Calculate the % of Cr in a sample of dichromate ore if 0.5g of the sample after fusion in regular way is treated with 50 ml of 0.12 N ferrous ammonium sulphate and the excess of Fe+2 requires 15.05 ml of K2Cr2O7. (1ml of K2Cr2O7 = 0.006 g Fe] Also find % of Cr2O3 in sample. [Ans : 15.20%, 22.23%] 0.804g sample of iron ore was dissolved in acid. Iron was reduced to +2 state and it required 47.2 ml of 0.112 N KMnO4 solution for titration. Calculate % of Fe and Fe3O4 in ore [Ans : 36.82%, 50.84 %] A solution is containing 2.52 g litre-1 of a reductant. 25 ml of this solution required 20 ml of 0.01 M KMnO4 in acid medium for oxidation. Find the mol.wt. of reductant. Given that each of the two atoms which undergo oxidation per molecule of reductant, suffer an increase in oxidation state by one unit. [Ans : 126] In a quality control analysis for sulphur impurity 5.6 g steel sample was burnt in a stream of oxygen and sulphur was converted into SO2 gas. The SO2 was then oxidized to sulphate by using H2O2 solution to which had been added 30 ml of 0.04 M NaOH. The equation for reaction is SO2(g) + H2O2(aq) + 2OH-(aq) ® SO-2 4(aq) + 2H2O(l). 22.48 ml of 0.024 M HCl required to neutralize the base remaining after oxidation reaction. Calculate % of sulphur in given sample [Ans : 0.1887%] 0.108 g of finely divided copper was treated with an excess of ferric sulphate solution until copper was completely dissolved. The solution after the addition of excess dilute sulphuric acid required 33.7ml of 0.1N KMnO4 for complete oxidation. Find the equation which represents the reaction between metallic copper and ferric sulphate solution. At. Wt. Of Cu=63.6, Fe=56. [Ans: Cu+Fe2(SO4)3 ® CuSO4+2FeSO4} A solid mixture (5.0g) consisting of lead nitrate and sodium nitrate was heated below 6000C until the mass of the residue was constant. If the loss in mass is 28.0%, find the masses of lead nitrate and sodium nitrate in the mixture. [Ans: 1.68g] Pathi * 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 31-08-06 Upon mixing 45.0ml of 0.25M lead nitrate solution with 25.0ml of 0.10M chromic sulphate solution, precipitation of lead sulphate taken place. What amount of lead sulphate is formed? Also, calculate the molar concentrations of the species left behind in the final solution. Assume that lead sulphate is completely insoluble. [Ans: 7.5´10-3 mol] Ten grams of a sample of bleaching powder were extracted with water and the solution made upto one litre. 25ml of this solution was added to 50ml of N/14 Mohr’s salt solution containing enough sulphuric acid. After the reaction was completed, the whole solution required 22ml of KMnO4 solution containing 2.2571g of KMnO4 per litre for complete oxidation. Calculate the percentage of available chlorine in the sample of bleaching powder. One gram of a mixture of anhydrous Na2CO3 and K2CO3 was dissolved in water and volume of the solution was made upto 250ml. 25ml of this solution required 26.25ml of HCl of unknown concentration for complete neutralization. The neutral solution so obtained required 16.25ml of 0.1M AgNO3 for complete precipitation. Calculate (a) the percentage of K2CO3 in the mixture and (b) the concentration of HCl in grams per litre. [Ans: 59.84, 2.26g] A mixture containing only FeCl3 and AlCl3 weights 5.95g. The chlorides are converted into the hydrous oxides and ignited to Fe2O3 and Al2O3. The oxide mixture weighs 2.62g. Calculate the percent Fe and Al in the original mixture. [Ans: 18.24, 9.50] 2.8g of an ammonium salt when heated with excess of NaOH solution and the gas evolved was passed into 150 cm3 of 0.25M H2SO4. The residual acid required 63.0 cm3 of 0.5M NaOH for complete neutralization. Calculate the percentage of ammonia in the ammonium salt. 1.64g of a mixture of CaCO3 and MgCO3 was dissolved in 50ml of 0.8M HCl. The excess of acid required 16ml of 0.25M NaOH for neutralization. Calculate the percentage of CaCO3 and MgCO3 in the sample. [Ans: 52.02 mass % MgCO3 and 47.98 mass % CaCO3] A solution contains a mixture of sulphuric acid and oxalic acid, 25ml of the solution requires 35.5ml of 0.1M NaOH for neutralization and 23.45ml of 0.02M KMnO4 for oxidation. Calculate the molarity of solution with respect to sulphuric acid and oxalic acid. [Ans: 0.0241M H2SO4 and 0.0469M oxalic acid] A 0.527g sample of a mixture containing Na2CO3, NaHCO3 and inert impurities is titrated with 0.109M HCl, requiring 15.7ml to reach the phenolphthalein aend point and a total of 43.8ml to reach the modified methyl orange and point. What is the percent each of Na2CO3 and NaHCO3 in the mixture? [Ans: 34.42% Na2CO3 and 21.54% NaHCO3] A 0.224g sample that contained only BaCl2 and KBr required 19.7ml of 0.100M AgNO3 to reach the end point. Calculate the percent of each compound present in the sample? [Ans: 32.4% BaCl2 and 67.7% KBr] A 0.510g sample of a pesticide was decomposed by fusion with sodium carbonate and bleaching the residue with hot water. The fluoride present in the sample was then precipitated s PbCIF by addition of HCl and Pb(NO3)2. The precipitate was filtered, washed, and dissolved in 5% HNO3. The Cl – was precipitated by addition of 50.0ml of 0.20M AgNO3. After coating the AgCl with nitrobenzene, the excess Ag+ was back-titrated with 7.42ml of 0.176M NH4SCN. Calculate the percent F - and the percent Na2SeF6 in the sample. [Ans: 32.4% F - and 67.9% Na2SeF3] A 0.517g sample containing Ba(SCN)2 was dissolved in a bicarbonate solution. 50.0ml of 0.107N iodine was added, and the mixture was allowed to stand for 5 min. The solution was then acidified, and the excess I2 was titrated with 16.3ml of 0.0965M sodium thiosulphate. Write a balanced equation for the oxidation of SCN - by I2, given that the product obtained from SCN - are SO 2 and HCN. 4 Calculate the percent Ba(SCN)2 in the sample. Pathi * 35. 36. 37. 38. 39. 40. 41. 42. é Ans: SCN + 3I2 + 4H 2O ‡ˆˆ ˆˆ † SO + HCN+7H + 6I 15.4% ù ë û A 1.850g sample of a mixture of CuCl2 and CuBr2 was dissolved in water and mixed thoroughly with a 1.80g portion of AgCl. After the reaction the solid, which now considered a mixture of AgCl and AgBr, was filtered, washed, and dried. Its mass was found to be 2.052g. What percent by mass of the original mixture was CuBr2? [Ans: 34.2] A mixture of two monoprotic acids, lactic acid (HC3H5O3) and caporic acid (HC6H11O2), was titrated with 0.05M NaOH. A 0.10g sample of the mixture required 20.4ml of the base. What was the mass of each acid in the sample? [Ans: 0.064g lactic acid and 0.036g caporic acid] A mixture of CaCl2 and NaCl weighing 2.385g was dissolved in water and treated with a solution of sodium oxalate which produced a precipitate of calcium oxalate. The precipitate was filtered from the mixture and then dissolved in HCl to give oxalic acid which when titrated against 0.2M KMnO4 consumed 19.64ml of the latter. What was percentage by mass of CaCl2 in the original sample? [Ans: 45.70% CaCl2] How many ml of 0.1N HCl are required to react completely with 1g mixture of Na2CO3 and NaHCO3 containing equimolar amounts of two? [Ans: V=157.8 ml] A certain solution consists of Na2CO3 and NaHCO3, 30ml of this required 12ml of 0.1N H2SO4 using phenolphthalein as indicator. In presence of methyl orange, 30ml of same solution required 40ml of 0.1N H2SO4. Calculate the amount of Na2CO3 and NaHCO3 per litre in mixture. [Ans: Strength of Na2CO3 = 4.24g litre-1, NaHCO3 = 4.48g litre-1] 50ml of a solution, containing 1g each of Na2CO3, NaHCO3 and NaOH was titrated with N HCl. What will be the titre readings if (a) only phenolphthalein is used as indicator? (b) only methyl orange is used as indicator from the very beginning? (c) methyl orange is added after the first end point with phenolphthaelein? [Ans: V1= 34.4ml, V2=55.8ml, V3=21.3ml] Zinc can be determined volumetrically by the precipitation reactions. 3Zn+2+.2 K4 [ Fe(CN)6 ] ® K 2 Zn 3 [ Fe(CN)6 ]2 + 6K + A sample of zinc ore weighing 1.5432g was prepared for reaction and required 34.68ml of 0.1043M K4Fe(CN)6 for titration. What is the % of zinc in ore? [Ans: % purity of Zn+22.85%] From the following data, calculate the for make of the hydrated potassium acid oxalate A, whose composition can be represented by the formula. xH2C2O4.yK2C2O4.zH2O. 10gms of A dissolved in water and made upto 1 litre 20 c.c of this solution required in separate experiments and under the usual laboratory conditions. N N (1) 29.5 c.c of NaOH (2) 39.4 c.c of KMnO4 10 10 [Ans: 5.31 gms, K2C2O4 3H2C2O4.2H2O] 24 + - Pathi * 31-08-06 43. 31-08-06 (i) A piece of plumber’s solder weighing 5g was dissolved in dilute nitric acid, then treated with dilute H2SO4. This precipitated the lead as PbSO4, which after washing and drying weighed 2.93g. The solution was then neutralized to precipitate the stannic acid, which was decomposed by heating, yielding 1.27g SnO2. What is the analysis of the solder as % Pb and % Sn? (ii) An acid solution of a KReO4 sample containing 26.83mg of combined rhenium was reduced by passage through a column of granulated zinc. The effluent solution, including the washings from the column, was then titrated with 0.1N KMnO4. 11.45mL of the standard permanganate was required for the reoxidation of all the rhenium to the perrhenate ion, ReO4-. Assuming that rhenium was the only element reduced. What is the oxidation state to which rhenium was reduced by the zinc column? [Ans: -1] 1.249g of a sample of pure BaCO3 and impure CaCO3 containing some CaO was treated with dil.HCl and it evolved 168ml of CO2 at NTP. From this solution, BaCrO4 was precipitatnd washed. The precipitate was dissolved in dilute sulphuric acid and diluted to 100ml. 10ml of this solution, when treated with Kl solution, liberated iodine which required exactly 20ml of 0.05N Na2S2O3. Calculate the percentage of CaO in the sample. [Ans: 14.09] A 2.0g sample of a mixture containing sodium carbonate, sodium bicarbonate and sodium sulphate is heated till the evolution of CO2 ceases. The volume CO2 at 750mm Hg pressure and at 298K is measured to be 123.9 ml. A 1.5g of the sample requires 150ml of M/10 HCl for complete neutralization. Calculate the percentage composition of the components of the mixture [Ans: 31.5] Pathi * 44. 45.
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