STPM Chemistry (Semester 2) STPM CHEMISTRY SEMESTER 2 PRE-EXAM PRACTICE Section A: Structured Questions Answer all questions. 1 (a) Chrome yellow has been used for a long time as a yellow pigment in oil paintings. SO42-(aq) + 4H+(aq) + 2e ⇌ 2H2O(l) + SO2(g) Eo = +0.17 V CrO42-(aq) + 8H+(aq) + 3e ⇌ 4H2O(l) + Cr3+(aq) Eo = +1.33 V (i) By using the standard electrode potentials above, explain why the yellow colour of the painting exposed to an atmosphere contains sulphur dioxide. [2 marks] (ii) Explain why this colour change takes a long time. [2 marks] .......................................................................................................................................... .......................................................................................................................................... (iii) What colour change takes place? [1 mark] .......................................................................................................................................... Li+(g) + Cl(g) (b) +121 1 Li+(g) + 2Cl2(g) −364 Li+(g) + Cl-(g) +520 1 Li(g) + 2Cl2(g) +159 1 Li(s) + 2Cl2(g) −409 Li+Cl-(s) -1- H6 STPM Chemistry (Semester 2) (i) By using this cycle, calculate the lattice energy of lithium chloride. [2 marks] (ii) Hence, calculate the enthalpy change of solution of lithium chloride. [2 marks] (iii) Comment on the solubility of lithium chloride in water. [1 mark] .......................................................................................................................................... Trg 2010 -2- STPM Chemistry (Semester 2) 2 (a) A Group 14 element forms a divalent ion that decolourises aqueous acidified potassium manganite(VII). (i) Name the element. [1 mark] .......................................................................................................................................... (ii) Write the equation for the reaction between the ion and acidified manganate(VII) ion. [1 mark] .......................................................................................................................................... (b) Nitrogen exists in the atmosphere as N2 molecules. Nitrogen is inert. (i) Explain the inertness of nitrogen. [1 mark] .......................................................................................................................................... (ii) Give two examples (other than the Haber process) of reactions involving atmospheric nitrogen. [2 marks] .......................................................................................................................................... .......................................................................................................................................... (c) In the laboratory, nitrogen is prepared by heating a mixture of ammonium chloride and sodium nitrate(III). (i) Write a balanced equation to represent the action of heat on the mixture. [1 mark] .......................................................................................................................................... (ii) State the changes in oxidation states of nitrogen in the reaction. [1 mark] .......................................................................................................................................... (iii) Nitrogen is also prepared by heating solid ammonium nitrate(III). Explain why these method is considered dangerous. [1 mark] .......................................................................................................................................... (d) Why is the presence of nitrogen dioxide in air polluting? [1 mark] .......................................................................................................................................... (e) Describe how oxides of nitrogen is eliminated from the exhaust gas by the use of a catalytic converter. [1 mark] .......................................................................................................................................... Trg 2010 -3- STPM Chemistry (Semester 2) 3 (a) When ammonium nitrate is heated, it liberates a colourless gas. The gas can be used as anaesthetic. (i) Name the gas. [1 mark] .......................................................................................................................................... (ii) Write the equation for the above reaction. [1 mark] .......................................................................................................................................... (iii) On the axes below, sketch the general trend in melting points for the Period 3 elements. Explain the trend. [4 marks] Melting point (oC) Na Mg Al Si P S Elements .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... (b) Chromium is a d-block element. Chromium compounds are used widely in the laboratory. (i) Write the electronic configuration of Cr3+ ion. [1 mark] .......................................................................................................................................... (ii) Briefly explain why the Cr3+(aq) ion is coloured. [3 marks] .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... Trg 2009 -4- .....f).............................. Draw a fully labelled diagram to show the cell that you will set up............588 V (i) Identify the strongest oxidising agent and the strongest reducing agent................................ (ii) You wish to build an electrochemical cell that will produce the highest possible electromotive force (e..88 V MnO4.776 V H2O2 + 2e ⇌ 2OH- Eored = 0.... Calculate the e........................................... Strongest reducing agent : ............ H2O2 + 2H+ + 2e ⇌ 2H2O Eored = 1.. -5- [4 marks] ..........m..........................+ 8H+ + 5e ⇌ Mn2+ + 4H2O Eored = 1..........STPM Chemistry (Semester 2) 4 (a) Refer to the data given below for questions 4(a)(i) – (ii).................f of this cell.... [3 marks] Strongest oxidising agent : ..........+ 2H2O + 3e ⇌ MnO2 + 4OH- Eored = 0..........................m.... Write an equation for the reaction between the two of them...... Equation : ......491 V MnO4...................... ............................. .......................... [2 marks] .............................................. Compound Decomposition BeCO3 MgCO3 CaCO3 BaCO3 T 540 900 1360 temperature (oC) (i) Predict T.......................................................................... SMJKST -6- .......................................................................................................................................................................................................................STPM Chemistry (Semester 2) (b) The table below shows the data about the carbonates of Group 2 elements.............. (ii) Explain the trend in decomposition by heat of Group 2 carbonates...... [1 mark] ........ ....................... examples CCl4........................... (ii) Write a balanced equation for the hydrolysis of SiCl4............................................................................................................................. SiCl4................... (i) State the molecular shape of all the Group 14 tetrachlorides............................ All the tetrachlorides..................................................................................... Aqueous ammonia is added to aqueous aluminium sulphate until in excess......................................... .................................................................................... with exception of CCl4................... (iii) Explain why CCl4 does not undergo hydrolysis......... (b) Aqueous aluminium sulphate contains [Al(H2O)6]3+.... (iv) What chemical nature of the aluminium ion is shown in (b)(iii)? [1 mark] ................... [1 mark] ..................................................................................................................... [2 marks] ........... GeCl4........ [1 mark] ....................................................STPM Chemistry (Semester 2) 5 (a) The tetrachlorides of Group 14 elements.. ....................................................................................................................... [1 mark] .............................................................................................. [3 marks] ......................................................................................................................................... (iii) What happens when excess aqueous ammonia is added to the solution? Write an equation for the reaction involved................................................................. SMI -7- ......... (ii) What chemical nature of the aluminium ion is shown in (b)(i)? [1 mark] ............................................................................................................................... SnCl4 and PbCl4 are liquids at room temperature.................................................................................. ........................................... The reaction that occurs in limited aqueous ammonia is as follow: [Al(H2O)6]3+(aq) + 3OH-(aq) Al(H2O)3(OH)3(s) + 3H2O(l) (i) Describe one observation in the above reaction............................... are hydrolysed in aqueous solution to form acidic solutions................ STPM Chemistry (Semester 2) 6 (a) (i) Write the electronic configuration of the scandium atom and scandium(III) ion............... (b) Chlorine is a greenish-yellow poisonous gas which is slightly soluble in water............ Pahang 2011 -8- ..... (i) Write a balanced equation for the reaction that occurs when chlorine gas is passed into water................................................................................................................................ Sc [2 marks] : .............................................................................................. Sc3+ : ............................................................................................................................................................................... [1 mark] .............................................................................................. (ii) State the colour of scandium(III) ion............. (ii) What would you observe when an excess of potassium iodide is added to the solution obtained from the reaction and write the equation for the reaction................. [2 marks] ................................................... (i) Name the halide ion in the sodium salt.................................. (c) A sodium halide reacts with cold concentrated sulphuric acid to give colourless fumes...................................... Sc3+ and explain why the colour is such................... the mixture produces brown fumes............................................................... (ii) Write two balanced equations to explain the observations above........................................................................................... ............................................................................................................................................................................................................................. Sc3+............................ [2 marks] ........................................................................ [2 marks] ..................... When heated....................................... .............................................................................................................. [1 mark] ..................... ........ ...................................................................... [2 marks] ...........................................................................027 0.............................................. ..................................................................................................... Sr2+ ion : ................................................................................. (b) The carbonates of the Group 2 elements decompose on heating...136 (i) Write the electronic configuration of Mg2+ ion and Sr2+ ion.......................072 0.......................................................099 0...............113 0....................................................................................................... carbonate does not decompose [2 marks] ...... (ii) How would you expect the ionic radius of Al3+ ion to be compared to that of Mg2+ ion? Explain your answer........................................................... Ion Be2+ Mg2+ Ca2+ Sr2+ Ba2+ Ionic radius (nm) 0............................. (iii) The hydrated Be2+ ion has the formula [Be(H2O)4]2+............................... (ii) Explain why magnesium spontaneously................... [1 mark] ........................... (i) Write the chemical equation for the decomposition of magnesium carbonate............................................................................................................. .................................................................................................................................................................................................................................... Suggest an explanation for the effect of the size of the cation on the thermal stabilities of the carbonates................................................STPM Chemistry (Semester 2) 7 (a) The ionic radius of the Group 2 elements is given in the table below.................................................................... .............. [2 marks] ................................................................... [1 mark] ..... (iii) The thermal stability of the carbonates increases with the proton number of the element.................. Pahang 10 -9- ............. [2 marks] Mg2+ ion : ....................... State one property shown by beryllium salts in water.................. ................. [Be(H2O)4]2+................................................................................................................................................................................................................................................................................................................... (c) Explain briefly why beryllium ion forms covalent compounds compared to other elements in the same group...................................................................................................................10 - ......................................................... (d) Nitric(V) acid is manufactured from ammonia in the Ostwald Process................................................... ............... [1 mark] ................................................... ....................................................................................................................................................................... [1 mark] ..................... [2 marks] ............................................................................................................................................... from beryllium to barium................. ............................................................................................................................................................................................................. .......................................................... (b) (i) Write a balanced equation for the reaction of hydrated beryllium ion............................ [1 mark] ......................................................................... in water............................................ (iii) Predict qualitatively the conditions of temperature and pressure that will give a maximum yield of nitrogen monoxide at equilibrium............................................ (ii) What is the property exhibited by the hydrated beryllium ion in the reaction above? [1 mark] ..................................................... (i) Name the catalyst used in this reaction........................................................................................................................................... [2 marks] .................................................. (ii) Write equation to show the formation of nitrogen monoxide in the Ostwald Process................................. ..... Pahang 2009 .........................STPM Chemistry (Semester 2) 8 (a) Explain why the reactivity of Group 2 elements in the Periodic Table increases when descending the group................................................ [2 marks] .............. .......................... .................. (c) How does the solubilities of the Group 2 sulphates change when moving down the group? Explain your answer............ ....... (ii) The elements in Period 3.............................................................................................................. (i) Write the equation for the decomposition of magnesium nitrate.................................................. [3 marks] ......................STPM Chemistry (Semester 2) 9 (a) The table below shows the structures of the elements in Period 3 in the Periodic Table from Na to Cl............................................................................................................................11 - ............... Element Structure Na Mg Al Si Giant metallic structure P S Cl Simple molecular (i) What is the structure of silicon? [1 mark] .............................................................................................................................................................. (iii) Draw the Lewis diagram for SO2............................................................................................. State the acid-base property of these oxides............................................... NS 11 ............ [3 marks] . ................................................................................................................................................ ............................................................... ......... [1 mark] ..................................................................................................................................... .......................................................... ........................................................................................................................................... from Na to S burn in oxygen when heated to form their respective oxides....................................................................................................................... (b) [1 mark] The nitrates of Group 2 elements decompose on heating................................................................ (ii) What is observed when magnesium nitrate is heated strongly? [1 mark] .................................................................................................................................. .............................. [2 marks] ....................... ..........STPM Chemistry (Semester 2) 10 (a) Carbon dioxide and nitrogen dioxide are gaseous combustion products of liquid hydrocyanic acid.... nitrogen dioxide and water are − 393 kJ mol-1.......................................... ................................................. − 89 kJ mol-1 and − 286 kJ mol-1 respectively............................................. (i) Define the standard enthalpy change of combustion of hydrocyanic acid.. Water is also formed in the combustion...................................................................................................................t...............p when the current used is 1.................................................................................... Calculate the standard enthalpy change of formation of hydrocyanic acid.................... HCN at 298 K and 1 atm.............. The standard enthalpy changes of formation of carbon dioxide...100 mol dm-3 sulphuric acid is electrolysed in an electrolytic cell using graphite electrodes................. ....... [2 marks] ..... Write a thermochemical equation for this enthalpy change.......................12 - ................................................. Calculate the time of electrolysis required to produce 140 cm3 of gas at the anode at s.........25 A.......................................... (b) An aqueous solution of 0................................................ [3 marks] (iii) Name the shapes of carbon dioxide and nitrogen dioxide................................ [3 marks] NS 2010 .... (ii) The standard enthalpy change of combustion of hydrocyanic acid is − 1628 kJ mol-1................. ..................................................................................................................................... .................................... NS 2010 .............................................................................................................................................13 - .............................................. [2 marks] (ii) State two properties of iron that enable it to form complex ions.......................................................................................................................................... ..............................................................................STPM Chemistry (Semester 2) 11 (a) Aqueous ammonia is added to aqueous aluminium sulphate slowly until in excess.................................................................................. [2 marks] ....................................................................... Complex Colour [Fe(CN)6]2- Yellowish-green [Fe(SCN)(H2O)5]2+ Red Name (i) Write the names of the iron complexes in the above table.................................... (ii) Write an equation for your observation above........... (iii) What will be observed at the end of the reaction after excess ammonia is added? Write the formula of the aluminium species at the end of the reaction...................................................................... ................................. ........ ................................................................................................................................................................................................................. [1 mark] ............................................................................................................................................. (iii) Why are transition metal complex ions coloured? [2 marks] ........................................... ..................... (i) What will be observed when aqueous ammonia is added slowly? [1 mark] ................................................... [2 marks] ...................................................................................................................................................................... (b) The table below shows two iron complexes............ ........................................................................................... Sr is an element in Group 2 of the Periodic Table.............. (d) Arrange the solubilities of Group 2 sulphates in descending order...................... Give only one formula for each element.............................................. [2 marks] ............................................. NS 09 ..............................14 - ............STPM Chemistry (Semester 2) 12 (a) Write the formula of the oxides of Period 3 elements of the Periodic Table in the table below........................................................... (ii) Aqueous hydrochloric acid............................................................................................................................................................ (i) Write a balanced equation for the action of heat on strontium nitrate................................................. ............................... [1 mark] .................... [1 mark] ............................................................................................................................... Element Na Mg Al Si [3 marks] S Cl Formula of oxide (b) Write equations for the reactions of aluminium oxide with the following reagents.................................................... (ii) Both magnesium nitrate and strontium nitrate will decompose on heating......................................................................................................................................................................... (i) Aqueous sodium hydroxide........ (iii) Explain your answer in (c)(ii)...................................................................... [1 mark] .................... (c) Strontium......................................... Which of the two will decomposes at a lower temperature? [1 mark] .... [1 mark] ................................. .................. .......................... [1 mark] ................................................STPM Chemistry (Semester 2) 13 (a) The yellow gas...... (b) The standard electrode potentials of the following systems are given below............. [4 marks] Comment: ............ .............................. [1 mark] ............................ predict whether chlorine dioxide in an acidic solution reacts with aqueous hydrogen sulphide.........15 - . System Eo / V ClO2(aq) + 4H+(aq) + 5e ⇌ Cl-(aq) + 2H2O(l) +1.... Calculate and comment on the value of the standard enthalpy of formation of chlorine dioxide................................................... chlorine dioxide..... 2AgClO3(s) + Cl2(g) 2AgCl(s) + 2ClO2(g) + O2(g) H = 0 kJ (i) Give the oxidation state of Cl in ClO2........................................................................................ Write a balanced equation to illustrate the reaction that occurs.............. [4 marks] Melaka 2009 . ClO2...........14 By using the standard electrode potentials given above......................................................50 S(s) + 2H+(aq) + 2e ⇌ H2S(aq) +0...................... (ii) Chlorine dioxide disproportionates to form a mixture of chlorate(III) and chlorate(V) ions in alkaline solution............ Give your reason.................................................. It can be made in the laboratory by the following reaction.............................................. (iii) Given that the standard enthalpies of formation of AgClO3 and AgCl are −25 kJ mol-1 and −127 kJ mol-1 respectively........... has been used for many years as flour-improving agent in bread making........... ..............54 (i) Draw a labelled diagram to show how the cell potential of an electrochemical cell consisting copper and silver half-cells can be measured....... show the direction of electron flow in the circuit...... (v) Calculate the standard cell potential..... [1 mark] .............................80 I2 + e ⇌ I- +0.............. [1 mark] (iii) Write the cell diagram for the above set-up...............34 Fe3+ + e ⇌ Fe2+ +0.................................................................................................STPM Chemistry (Semester 2) 14 Several standard electrode potentials are shown below.................... Eo / V Half-cell Ag+ + e ⇌ Ag 1 Cl2 + e ⇌ Cl- +1......... [2 marks] (ii) On the diagram..... [1 mark] (vi) Calculate the cell potential if the solution containing silver ions is replaced with 0.. [1 mark] ..........77 2 1 2 (a) +0............ (iv) Write the overall cell reaction.36 Cu2+ + 2e ⇌ Cu +0....16 - .............................10 mol dm-3 aqueous silver nitrate while other factors remain unchanged.... [2 marks] ......... ................ Explain why by using the electrode potentials data................................................................................................ ............................................................... Kelantan 12 ........................................................................................ [2 marks] .................................... ...........................STPM Chemistry (Semester 2) (b) Chlorine will oxidises Fe2+ to Fe3+ but iodine does not..............................................17 - .............................................. ............................................................................................................................................................................................................................................................... copper(II) sulphate solution.................. …............... (iii) Explain why transition element complex are often coloured.......................... …........... Aqueous ammonia is added to copper(II) The blue precipitate dissolves and sulphate solution until in excess............STPM Chemistry (Semester 2) 15 (a) (i) Explain the term complex ion............ [3 marks] …...................................... [2 marks] …........................................................................................................................................................... [2 marks] …............................................................................................................................................................. The table below shows the observations obtained................................................................................................... [1 mark] …........................................................ …...... …..................... (b) A series of experiments were carried out on an aqueous solution of copper(II) sulphate....................................................................... [2 marks] …..................................................................................................2-ethenediamine is a chelating ligand............................... …. Kelantan 12 ........................................ Explain your answer...... …........................................................ Explain the term chelating ligand...............................................................................................18 - ..................................................................................... …........................................... whereas compounds of other elements are usually white................................................... (ii) 1......... (i) Write down the formulae of all the complex ions in the experiments................................................................................................................. …........................................................ a dark blue solution is obtained.......................................... (ii) Arrange the ligands in order of increasing strength with respect to copper(II) ions............. Experiment Observation Aqueous sodium hydroxide is added to A blue precipitate is formed................................................................................. ......................................................... (b) Give a difference in terms of bonding and structure between glass and ionic crystal........ SiO2....................................................................................................................... (i) In the following table.........................................................................STPM Chemistry (Semester 2) 16 An important use of silicon compounds is to make glass................................................................................................................... (ii) give a coloured product............................................ ............................ (a) Name a substance which can be added to soda glass in order to (i) increase its melting point.............................................................................................................. [1 mark] ........................ Kelantan 2009 ........ [2 marks] ......................................................................................................... [4 marks] Action of water Equation of reaction CCl4 SiCl4 PbCl4 (ii) Explain the differences of the reaction between the three tetrachlorides above with water............... ..................... ................ [2 marks] .......................................................................... The simplest form of glass is soda glass which is produced by melting silica................ sodium carbonate and calcium carbonate at about 1800 K............................................................................................................. give the name of the process (if any) and the equation for the reaction which occurs.......................................................... [1 mark] ....... .................................. (c) Group 14 elements can react with chlorine to form tetrachlorides.....................................19 - ....................................... ....... [1 mark] .......................... .......... (ii) State one use of optical fibre.....................................60 Sn4+(aq) + 2e ⇌ Sn2+(aq) +0....................................20 - .. ............................................................................................................. ................................. ....................................................................... ........................................................................... A laser beam can travel along an optical fibre which is as thin as human hair............. at 298 K............................................................ State two advantages of optical fibres over copper wire........................................................................................................................................... (ii) Which ion is the strongest reducing agent? [1 mark] ........................... [1 mark] ........................ optical fibres have many advantages over copper wire.................................................................................................................................. [2 marks] ...................................................................................................................... ......... (i) State the main component of glass................... (iii) In certain applications.. (iii) Which ion is more stable in aqueous solutions....................... (b) An important application of glass is to make optical fibres.........................................................STPM Chemistry (Semester 2) 17 (a) The standard electrode potentials.................................................. .......................................................... Sn4+ and Pb4+ ions in order of decreasing stability in aqueous solutions........................................15 Pb4+(aq) + 2e ⇌ Pb2+(aq) +1........... (iv) State the difference in the structure between glass and diamond................................................................................. [1 mark] ............................................................... [2 marks] ....................................... [2 marks] ............................... Pb2+ or Pb4+? Explain your answer.............................80 (i) Arrange the Ge4+......................................................................................................................................................................................................... of some half-cells are given below..................... Eo / V Half-cells Ge4+(aq) + 2e ⇌ Ge2+(aq) −1................................................................................................................................................................... .................................................................................................................................... [1 mark] .. 4....... [3 marks] (b) Write the observation when sodium hydroxide solution is added to an aqueous solution of aluminium sulphate until in excess...................... Calculate the percentage yield of the product............................................. [1 mark] ................................................................................ [1 mark] .............................................. Al2Cl6 is formed when aluminium reacts with chlorine gas........................................... [1 mark] ............................................................ (iii) If 2........................... (ii) aluminium is not easily corroded as iron............................ (ii) hot aqueous sodium hydroxide.......... [1 mark] ............................................................................. [1 mark] .......................................STPM Chemistry (Semester 2) 18 (a) Aluminium chloride....................................................................................................................................................... Kedah 2009 ................................ [1 mark] .............................60 g of aluminium chloride would be produced....................00 g of aluminium was added in the reaction............................................................21 - .. (d) Write the chemical equations for the reaction of chlorine with (i) cold aqueous sodium hydroxide........... (c) Explain why (i) an aluminium pot should not be used to boil strongly alkaline soup. (i) Write a balanced chemical equation for the above reaction................................ (ii) State one important use of aluminium chloride.......................... ............. ...................................................................................... [2 marks] .......................................................f.......................... (iii) Write a cell diagram for the above reaction...........54 When an aqueous solution of potassium peroxodisulphate.................................22 - ............................. (i) Name the colourless gas..... Half-cell reaction Eo / V S2O82.. [1 mark] .....01 [Fe(CN)6]3.................................................................................................................................................. [2 marks] ...........36 Fe3+ + e Fe2+ +0................................................................................. A colourless and very reactive gas is given off.................................................................................................. (ii) Write the equation for the reaction between copper and nitric acid... ................................................... a reddish-brown solution is obtained.. [1 mark] ...... K2S2O8 is added to an aqueous solution of potassium iodide... KI........... The gas then reacts with oxygen in air to form a brown gas......... (iv) Calculate the standard cell e........................STPM Chemistry (Semester 2) 19 (a) (i) Give the definition of standard electrode potential................. [1 mark] (c) Strips of copper are dropped into a conical flask containing 50% hot nitric acid solution........+ 2e 2SO42- +2........................................+ e [Fe(CN6)]2- +0........................................... (ii) Write a balanced ionic equation for the above reaction........................... [1 mark] ........... Write equation for its formation..... [2 marks] ............................. Eocell for the reaction in (b)(iii)..................................................................77 I2 + 2e 2I- +0..................................... (iii) Identify the brown gas..............................................................................................m........ The standard reduction electrode potentials for several half-cell reactions at 298 K are given in the table below............................ ........ .................................. ..................... (c) The first electron affinity for oxygen atom is −141 kJ mol-1 whereas the second electron affinity is +798 kJ mol-1..............................................STPM Chemistry (Semester 2) 20 (a) Define the following............................................................................................................................... (ii) Give a brief account for the trend of temperature of decomposition of Group 2 nitrates................... (i) First electron affinity.................................................................................................................. [2 marks] ........................................ [1 mark] .......................................................................... ...... [3 marks] ....... Explain why the first electron affinity is exothermic while the second electron affinity is endothermic....................................................................................... [1 mark] .................................................. ......................................................................... [2 marks] First electron affinity : ...................................................23 - ........................................................ [1 mark] ............................................... (ii) Second electron affinity...................................................................... (b) Write equations to represent the first and second electron affinities for an oxygen atom.............................................................................................................................................................. ................................................................................................................... (d) The decomposition temperatures of nitrates of Group 2 elements is shown below........................................................................................................................................................................................................................................... Johor 10 ..................... Second electron affinity : ...................................................................................... ............................................................................................................ ...................................................................................................................... Nitrate Be(NO3)2 Mg(NO3)2 Ca(NO3)2 Sr(NO3)2 Ba(NO3)2 Temperature (K) 320 390 460 670 820 (i) Write a balanced equation for the decomposition of one of the nitrate.................................................... .............................. ................... ............. .............................. calculate the standard enthalpy of formation of calcium chloride........................ Ca2+(g) + 2Cl-(g) ....... .. ........ Ca(s) + Cl2(g) CaCl2(s) Standard enthalpy change Value / kJ mol-1 Enthalpy of atomisation of Cl +121 Enthalpy of atomisation of Ca +178 First ionization energy of Ca +590 Second ionization energy of Ca +1145 Electron affinity of Cl −364 Lattice energy of CaCl2 −2237 (a) Complete the Born-Haber cycle above............ (b) Using the cycle and the values given in the table..........................STPM Chemistry (Semester 2) 21 Consider the incomplete Born-Haber cycle and the table of data below............24 - [3 marks] [2 marks] ..................... Calculate the temperature change and the final temperature of the solution. (d) [2 marks] The standard enthalpy of solution of ammonium chloride.2 J K-1 g-1. Both substances are initially at 20oC.ions are −1650 kJ mol-1 and −364 kJ mol-1 respectively. Assume that the specific heat capacity of the solution is 4. [3 marks] . A 2. NH4Cl is +15 kJ mol-1.STPM Chemistry (Semester 2) (c) The standard enthalpies of hydration of the Ca2+ and Cl. Use this information and data from the table to calculate the enthalpy of solution of calcium chloride.0 g sample of ammonium chloride is dissolved in 50 g of water.25 - . ............................................................ (ii) Use your understanding of acids and bases to explain the role of aluminium chloride in the reaction above.................... (iii) State one property which enables aluminium to be used in overhead electric cables..... ......................................................................... [2 marks] .................... [1 mark] .... is formed............................................. Q........................................ [1 mark] ..................................... (ii) Give the formula of ion Q................................. (i) Describe what you would observe when aqueous sodium carbonate is added to aqueous aluminium chloride...................... The precipitate dissolves in excess sodium hydroxide........... (ii) Write an ionic equation for the reaction above................................................................. (b) When aqueous sodium hydroxide is added to an aqueous solution of aluminium chloride............. Johor 2009 ........................................................................................... .................................................... forming an ion............................................... [1 mark] ............................................................. (d) Aluminium chloride can be used as catalyst in Friedal Craft alkylation of benzene..............................................STPM Chemistry (Semester 2) 22 Aluminium is the first element of Group 13 in the Periodic Table..................................... (a) State the valence electronic configuration of aluminium.......................................... a white precipitate................................................................................................................................. [1 mark] ....................... P.......... [2 marks] .................................... (c) An aqueous solution of aluminium salt is acidic............................ [1 mark] ...................................................... ................................................. CH3Cl.................................... (i) Write an equation for the reaction between aluminium chloride and chloromethane........ [1 mark] ...................................................................................... .............................................26 - .................................................................................................................................................................................................................................................................................. to form an electrophile........................................ (i) Name the precipitate P.................................... ......................................................27 - .. (ii) Calculate the concentration of a saturated solution of ammonia.................................................................... (ii) Write a balanced equation to show how ammonium chloride can be used to prepare ammonia in the laboratory.................................................................................. ................... [2 marks] (iii) Describe and explain what happens when a saturated solution of ammonia is shaken with silver bromide.............................................. At room temperature........................................... .................................. .......................STPM Chemistry (Semester 2) 23 (a) Nitrogen can be produced by warming a mixture of ammonium chloride and sodium nitrite.................... [1 mark] ........................................................................................................................................................................................................................................................................................... ....................................................... (i) Suggest why ammonia is so soluble in water...............0 g of ammonia........ Write a balanced equation for the reaction....................... (i) Suggest an identity for the solid................ [2 marks] .................................................................................................................................................................................................................... Steam is also produced and a solid is left........................................................................................................ [2 marks] ....................................................................................... (b) Ammonia is very soluble in water........................... NaNO2. [2 marks] ........................................................... .................................................................................. 100 cm3 of its saturated solution contains 33................................ (iii) Explain why nitric acid is usually kept in dark bottles..... ........................................................................................................ [1 mark] .......... ......... in mol dm-3............ (b) [5 marks] Write a balanced reaction for the reaction in the cell below. Eo. 100 g of water was heated from 15oC to 65oC.28 - . (i) Bromine is added to cold.5 kJ mol-1 Enthalpy change of combustion of H = −285. Write a balanced equation for this reaction and explain how ammonia is behaving both as reducing agent and as a base. Fe2+(aq) | Pt(s) and calculate the standard electrode potential. (iii) When 1. (ii) Write a balanced equation for the complete combustion of ethanol. (ii) Concentrated sulphuric acid is added to solid potassium bromide and the mixture is heated. aqueous sodium hydroxide.STPM Chemistry (Semester 2) Section B (Essay Questions) Answer all questions. [3 marks] Johor 08 .00 g of ethanol was burned under a container of water. Calculate the enthalpy change of combustion per mole of ethanol. (c) [2 marks] (i) Explain the term standard enthalpy change of combustion. Cu(s) | Cu2+(aq) || Fe3+(aq) . explain how to determine the standard electrode potential for copper. (c) [3 marks] Suggest an explanation for the decreasing solubilities of the Group 2 sulphates as the proton number of cations increases. (b) [9 marks] Ammonia and chlorine react in the gas phase to give gaseous nitrogen and solid ammonium chloride.8 kJ mol-1 [9 marks] Johor 08 2 (a) Describe and explain what happens in each of the following experiments. calculate the enthalpy change of formation of ethanol from its elements. (iii) Aqueous silver nitrate is added to aqueous sodium chloride and aqueous ammonia is then added to the resulting mixture. 1 (a) With the help of a labelled diagram. Enthalpy change of combustion of C = −393. (iv) Using the value you have calculated in (iii) and the following data. Write balanced equations for the reactions that occur. The process was known to be only 70% efficient. of this cell. State the observations and the type of reaction. [1 mark] (ii) State what you would observe when chlorine water reacts with solution of potassium iodide. (i) Write an expression for the Ksp of magnesium hydroxide. Write an equation for the reaction. State what would be observed in each case. [5 marks] Johor 09 4 (a) An aqueous solution of magnesium nitrate and barium nitrate can be differentiated by the addition of dilute sulphuric acid. State what you would observe when the above reaction is carried out. State how each chloride behaves and explain the difference. [6 marks] (b) Carbon tetrachloride and silicon tetrachloride behave in different ways when added into water. State the role of chlorine in the reaction.1 mol dm-3 MgSO4(aq) than in water. Ksp. (iii) Explain whether magnesium hydroxide would be more soluble or less soluble in 0. stating its unit. Write an equation for one of the reactions. for the solid sulphates formed in (a). (ii) Use the value of Ksp given to calculate the concentration of Mg(OH)2 in a saturated solution. [5 marks] Johor 09 .29 - .STPM Chemistry (Semester 2) 3 (a) (i) State the trend in the reducing ability of the halide ions from fluoride to iodide. [3 marks] (iii) Name a reagent which can be used to distinguish between separate solutions of potassium bromide and potassium iodide. of magnesium hydroxide has a numerical value of 2.0 × 10-11. State what would be observed when this reagent is added to each of the solutions. (b) [3 marks] Compare and explain the solubility in water. (c) [7 marks] The solubility product. Identify a reagent which could be added to the mixtures from the first test to confirm the identities of the halide ions. what happens in each of the experiments below.30 - . state the cell diagrams and the standard electrode potential values for the following reactions. with equations. [4 marks] Fe(s) + Pb2+(aq) Fe2+(aq) + Pb(s) 2H+(aq) + Zn(s) Zn2+(aq) + H2(g) (b) Predict the product that would be obtained from the electrolysis of the following aqueous solutions using platinum electrodes. [7 marks] (b) Give two uses of aluminium and relate the uses to its properties. (i) Copper(II) chloride (ii) Hydrochloric acid (iii) Potassium hydroxide (c) [6 marks] An industrially important source of hydrogen is the reaction below. [1 mark] (ii) Using the Data Booklet. Substance Enthalpy change of combustion. [4 marks] (c) Explain why an aqueous solution of ammonia does not contain NH4OH molecule. CH4(g) + 2H2O(g) ⇌ CO2(g) + 4H2(g) Use the enthalpy changes of combustion given below to construct an energy cycle and use it to calculate the enthalpy change of this reaction. (d) [2 marks] Write an equation to show the role of ammonia as (i) base (ii) complexing agent [2 marks] Johor 10 . Hc / kJ mol-1 CH4 −890 H2 −242 CO2 −283 [4 marks] Johor 10 6 (a) Discuss. (i) Aluminium chloride is added to water containing a few drops of methyl orange indicator. (ii) A strong alkali is boiled vigorously in an aluminium pot.STPM Chemistry (Semester 2) 5 (a) (i) Define the term standard electrode potential. [2 marks] Kedah 09 .m. calculate the enthalpy change of the following reaction. identify the strongest oxidising agent and the strongest reducing agent. [2 marks] (ii) Using the data given below.31 - . 3MnO2(s) + 4Al(s) 2Al2O3(s) + 3Mn(s) Enthalpy change of formation of Al2O3 = -1670 kJ mol-1 Enthalpy change of formation of MnO2 = -520 kJ mol-1 [2 marks] (iii) Explain why this reaction is used to extract manganese from its ore.34 Zn2+(aq) + 2e.m. ?? / V Electrode Al3+(aq) + 3e.⇌ Al(s) -1. MnO2.f of the electrochemical cell in (a)(iii) when the concentration of Cu2+ ions in the copper half-cell increases? (b) [1 mark] (i) Explain standard enthalpy change of formation of MnO2. [2 marks] (ii) Describe what you would observe when zinc powder is added to aqueous bromine solution.8 mol dm-3) // Cu2+(aq.⇌ Fe(s) -0.76 (i) By using the data above. [2 marks] (iii) Calculate the e.04 Cu2+(aq) + 2e.⇌ 2Br-(aq) +1.66 Br2(l) + 2e. 0.⇌ Zn(s) -0. ? ? for a number of electrodes are given in the table below.f of the following electrochemical cell at 25oC.4 mol dm-3) / Cu(s) [4 marks] (iv) What is the effect on the e. 0.⇌ Cu(s) +0.STPM Chemistry (Semester 2) 7 (a) The standard electrode potentials.07 Fe3+(aq) + 3e. Al(s) / Al3+(aq. (i) Name this complex ion. SiO2 and P4O6 are 2040oC. Explain the differences in their melting points in terms of structure and bonding. [Molar gas volume = 24400 cm3] (b) (i) Write a balanced equation for the reaction. (c) [4 marks] [CrCl2(C2O4)2]3. [2 marks] Kedah 09 . [1 mark] (ii) Draw all the structural formulae of the isomers of this complex ion. 1610oC and 24oC respectively.is a complex ion. [1 mark] Arrange the acids HCl. [3 marks] (iii) Name the dimer of this oxide of nitrogen.STPM Chemistry (Semester 2) 8 (a) Oxides of the Period 3 elements include the following: Al2O3. [2 marks] (iii) Explain how these cracks appear when the wet clay dries out. P4O6 (i) The melting points of Al2O3. The reaction produced 1000 cm3 of nitrogen gas and the mass of copper is found to have increased by 2. (b) [4 marks] Montmorillonite is a type of silicate clay which cracks during dry season.71 g. (i) Draw the basic three dimensional structure of a silicate ion. reacted with pre-heated copper powder. [3 marks] (iii) State the types of isomerism exhibited by the isomers. SiO2. [2 marks] Kedah 09 9 (a) 2000 cm3 of a gaseous oxide of nitrogen. HBr and HI in increasing order of acid strength. NxOy. Explain your answer. [1 mark] (ii) Determine the formula of NxOy.32 - . All volume of gases are measured at room temperature and pressure. [1 mark] (ii) Draw a simple diagram to show the layered structure of montmorillonite. [6 marks] (ii) Describe the solubilities of the oxides in water and write balanced equations for the reaction of the oxides (if any) with water. 8 mol dm-3) // Cu2+(aq. 1 Cl2(g) + water + e. H2 = -364 kJ mol-1 Enthalpy change of hydration.m.f of the following electrochemical cell. (i) Using standard electrode potentials from the data booklet and the information given above.STPM Chemistry (Semester 2) 10 (a) The e.059 [?]? [?]? log ? [?]? [?]? with Ecell as the standard cell potential and n as the number of moles of electrons transferred in the reaction. [2 marks] Zn(s) / Zn2+(aq. Enthalpy change of atomisation. [5 marks] Zn(s) + Cu2+(aq) ⇌ Cu(s) + Zn2+(aq) (ii) Calculate the e. 0. calculate the enthalpy change for the reaction below. Use the following data to calculate the enthalpy change of this reaction.4 mol dm-3) / Cu(s) (b) One method of preparing sulphur dioxide in the laboratory is by mixing excess acid with an aqueous solution of sodium sulphite. [5 marks] Kedah 10 . Cl-(aq) 2 Deduce the strength of chlorine as an oxidising agent based on the value of H4 obtained.33 - . [3 marks] H / kJ mol-1 3 H2(g) + S(s) + 2O2(g) 2H+(aq) + SO32-(aq) -623 S(s) + O2(g) SO2(g) -296 1 H2(g) + O2(g) H2O(l) -286 2 (c) The following data are about chlorine. Kc for the following reaction. H1 = +121 kJ mol-1 Electron affinity. H3 = -381 kJ mol-1 By drawing an energy cycle.f of an electrochemical cell that involves the reaction aA + bB ⇌ cC + dD is given by the equation below ????? = ? ? ???? − 0.m. H4. 0. calculate the equilibrium constant. 00% Cl = 42.53% (i) Given the relative molecular mass of Q is 250.STPM Chemistry (Semester 2) 11 (a) Group 2 elements form carbonates. Co = 23.34 - . A catalytic converter removes this gas from the exhaust. [3 marks] (b) No visible change is recorded when a heated glass rod is placed in a gas jar containing hydrogen chloride vapour. a purple vapour formed when it is placed in another gas jar containing hydrogen iodide vapour. Al2O3. (i) Describe the extraction of aluminium from pure bauxite. [4 marks] Kedah 10 . By using suitable chemical equations. [3 marks] (c) A neutral. Determine the structural formula of Q. The percentage by mass of each element in the complex is as follow. Determine the molecular formula of Q. [5 marks] Kedah 10 12 (a) Nitrogen monoxide is found in exhaust gases of motorised vehicles. a colourless gas that turns lime water chalky is evolved. coloured compound. [4 marks] (ii) State one reason why aluminium metal is widely used in aerospace industry. (b) [5 marks] Aluminium is one widely used metal in industry. Q.52% N = 28. [1 mark] (c) When some sodium carbonate is added into aqueous aluminium sulphate. Aluminium is extracted mainly from pure bauxite. Explain the above observation and write all the equations involved. Explain these observations. MCO3. has the empirical formula Co(Cl)x(NH3)y.4. Explain the thermal stability of the carbonates descending the group. [4 marks] (ii) It is found that one mole of Q reacts with two moles of silver nitrate. explain the formation of nitrogen monoxide in the engine and how the gas is removed. [1 mark] (iii) Explain why Q is coloured. However. a solution of [Cu(H2O)6]2+ complex ion is blue but a solution of [CuCl2]. Enthalpy of atomisation of M = +284.complex ion is colourless. Explain these observations in terms of electronic configurations. (i) draw a Born-Haber cycle for the formation of MF.0 kJ mol-1 Electron affinity of F = -322. [2 marks] (iii) if the enthalpy of formation of MF2 is +342. [4 marks] Ktan 09 .6 kJ mol-1 First ionisation energy of M = +731. [1 mark] (b) Transition element complexes are often coloured whereas compounds of other metals are usually white.0 kJ mol-1 Lattice formation energy of MF = -969. For example. germanium. (b) [4 marks] The possible fluorides formed by an element M are MF and MF2. Describe the variation in acid-base character of their oxides. which compound will most probably be formed when M reacts with F. (c) [5 marks] (i) Carbon. the reaction that takes place is as follows: 2Mn2+ + 4H+ + 5PbO2 2MnO4.0 kJ mol-1 Second ionisation energy of M = +2073 kJ mol-1 Enthalpy of atomisation of F = +79. tin and lead are elements in Group 14 of the Periodic Table. Explain.35 - . [3 marks] Kelantan 09 14 (a) Explain the term transition element.6 kJ mol-1.+ 5Pb2+ + 2H2O Explain how lead(IV) oxide reacts.0 kJ mol-1 Lattice formation energy of MF2 = -2260 kJ mol-1 Using the data provided above.STPM Chemistry (Semester 2) 13 (a) Define the standard formation and lattice energy of sodium chloride crystalline. When lead(IV) oxide is heated with an aqueous solution of a manganese(II) salt in the presence of excess nitric(V) acid. [5 marks] (ii) Lead(IV) oxide is a dark-brown solid. [6 marks] (ii) calculate the enthalpy of formation of MF. and state the observations. silicon. 0 J K-1 g-1] (i) Define the heat of neutralisation.0 g) of aqueous hydrogen chloride (slightly in excess) contained in a polystyrene cup. [4 marks] (c) A complex compound. [Specific heat capacity of the solution = 4. [1 mark] (ii) Write a balanced equation for the combustion of octane in excess oxygen. [2 marks] (ii) Write a balanced equation for the above reaction.STPM Chemistry (Semester 2) 15 (a) 1. (iii) Explain what happens when an aqueous solution of silver nitrate is added to an aqueous solution of triaminetrichlorocobalt(III). [8 marks] Melaka 09 .0 cm3 (50. (v) (b) [1 mark] Why should the solution be stirred during the reaction? [1 mark] Octane. [3 marks] Hf of CO2 = −394 kJ mol-1 Hf of H2O = −286 kJ mol-1 Hf of C8H18 = −250 kJ mol-1 (iv) How is the knowledge of standard enthalpy of combustion useful to a chemist other than that as a fuel? [2 marks] Ktan 12 16 (a) Why does cobalt shows variable oxidation states? [3 marks] (b) Explain the term complex ion.36 - .00 g of solid potassium hydroxide was dropped into 50.0oC to 40. [1 mark] (iii) From the data provided. calculate the H for the reaction. (i) What is the chemical formula of triaminetrichlorocobalt(III)? (ii) Draw the structures of the two isomers and name them.0oC was recorded. A temperature change from 30. State the type of isomerism shown. [1 mark] (iii) Calculate the standard enthalpy of combustion of octane by using the following information. C8H18 is used as a fuel. [3 marks] (iv) Give one important reason why it is preferable to use a polystyrene cup over a glass beaker. triaminetrichlorocobalt(III) exists as two isomers. (i) Define the heat of combustion with respect to octane. [8 marks] NS 09 .6 cm3. [3 marks] Melaka 09 18 (a) 0. Identify each of these substances and explain the chemistry of the reactions involved. It reacts with water to form an acidic solution. [5 marks] Some properties of two substances X and Y are given below. Draw a displayed formula to show the types of bonding in the molecules of the vapour. (i) X is a colourless aqueous solution that leaves no residue on evaporation. [4 marks] (ii) Y is a compound of Group 14 elements. one of which reacts with water and the other does not.STPM Chemistry (Semester 2) 17 (a) Explain how the following changes down Group 2 (beryllium to barium) of the Periodic Table. (b) [4 marks] Explain with the help of equations why an aqueous solution of aluminium sulphate has a pH of 4.500 g of solid aluminium chloride was heated to 200oC at a pressure of 1. Silicon(IV) oxide is a solid that is insoluble and unreactive towards water. It is stable to heat even at high temperature. [3 marks] (ii) Thermal stability of the nitrates. (b) (i) Reactivity towards water. which exists as a colourless liquid at room temperature. Carbon dioxide is a gas that dissolves in and reacts with water. Write balanced equations for all reactions that occur.00 × 105 Pa. Explain the differences in physical and chemical properties of these four compounds described by these statements. The volume of vapour formed at this temperature and pressure was found to be 73. (c) [3 marks] Carbon and silicon are the first two elements in Group 14 of the Periodic Table.8. Write equations for the reactions involved. The tetrachlorides of carbon and silicon are both liquids.37 - . Calculate the relative molecular mass of the vapour at this temperature and pressure. and upon excess turns into a deep blue solution. It forms a blue solid with an aqueous solution of copper(II) ions. [7 marks] (b) The table below gives the standard reduction potentials. (c) [3 marks] Describe and explain what happens when an aqueous solution containing Cu2+ ions is added gradually with dilute aqueous ammonia followed by an aqueous solution of [EDTA]4-. (ii) Name one tetrachloride of Group 14 that reacts with water and write an equation for the reaction. [4 marks] NS 2010 21 (a) (i) What do you understand by anodizing of aluminium? (ii) Describe the method used to carry out this process. Explain the chemistry involved with the aid of balanced equations. followed by aqueous ammonia. [4 marks] .85 −2. (c) [4 marks] State and explain the thermal stability of the nitrates when descending Group 2 of the Periodic Table.87 −2. In each case. suggest the products of the reaction and write equations where appropriate.38 −2. (b) State and explain the thermal stability of Group 14 tetrachlorides from carbon to lead. Element Eo / V Be Mg Ca Sr Ba −1. Eo for Group 2 elements. amphoteric and acidic. (c) [7 marks] [4 marks] (i) Name one tetrachloride of Group 14 that does not react with water and explain why. (ii) concentrated sulphuric acid. bromide and iodide ions differ in their reactions with (i) silver nitrate solution. Describe the reactions of Period 3 elements with oxygen to form the above types of oxide.90 Explain the reactivity of Group 2 elements towards water by referring to the above standard reduction potential values. (b) [9 marks] What do you understand by the term transition element? State two properties of iron or its compounds that typify it as a transition element.38 - .STPM Chemistry (Semester 2) 19 (a) How do chloride.89 −2. [3 marks] NS 09 20 (a) Oxides of Period 3 elements are classified as basic. Mn2+ and Zn2+. The melting points of the elements are given below. (i) Write the electronic configurations for the ions Sc3+. [8 marks] Pahang 09 . (iii) Another complex of chromium has the formula [CrCl2(NH3)4]+. (c) [5 marks] A typical property of transition elements is their ability to form complexes. (b) [4 marks] The elements scandium. [6 marks] nS11 23 (a) The ore of aluminium is bauxite. (b) [7 marks] Aluminium. Draw the structural formulae for the two isomers of this complex.39 - . manganese and zinc are first row d-block elements in the Periodic Table. Explain. phosphorus and sulphur are Period 3 elements in the Periodic Table. Element Melting point (oC) Aluminium 660 Silicon 1410 Phosphorus 44 Sulphur 119 Explain the melting points of the elements in terms of structure and bonding.STPM Chemistry (Semester 2) 22 (a) Explain why the reaction between sodium halides with concentrated sulphuric acid can be used to prepare bromine but not chlorine. (ii) Explain the use of aluminium in aircraft construction. (i) Explain how the [Cr(NH3)6]3+ ion can be prepared from aqueous chromium(III) chloride. A complex of chromium has the formula [Cr(NH3)6]3+. (ii) Explain why Cr3+ ions have a great tendency to form such complexes. silicon. (ii) Which of the above ion(s) is / are colourless. (i) Briefly describe the extraction of aluminium from pure bauxite. Write balanced equations for any reactions that occur. (b) [4 marks] Explain why iodine is more soluble in potassium iodide solution than in water. [3 marks] Phg 10 + Johor 08 .STPM Chemistry (Semester 2) 24 (a) Explain why chlorine is used in the large scale preparation of bromine from sea water which contains bromide ions. (i) Draw all isomers with the formula [Co(H2NCH2CH2NH2)2Cl2]+. with the same formula as Y. Z. (c) [5 marks] Magnesium carbonate undergoes thermal decomposition at a much lower temperature (353oC) than barium carbonate (1430oC).25 mol dm-3. If the volume of hydrochloric acid needed to complete the titration is 15.00 mol dm-3 is electrolysed for 25 minutes using graphite electrodes. (ii) Which of the isomers could be the structure of Y and Z? Give your reason. (d) [4 marks] Explain what happens when solid potassium iodide is heated with concentrated sulphuric acid. The resulting solution is then treated with hydrochloric acid of concentration 0. Write balanced equations for the reactions that occur. calculate the magnitude of the current used during the electrolysis. Evaporation of an aqueous solution of Y at 90oC produces a red complex cation. H2N(CH2)CH2NH2 and HCl produces a green complex cation.50 cm3. whereas Z has. Explain in terms of structure and bonding. Y has no dipole moment. (b) Passing air through an [7 marks] aqueous solution containing CoCl2. with formula [Co(H2NCH2CH2NH2)2Cl2]+. [3 marks] Phg 09 25 (a) A solution of sodium chloride of concentration 2. Y.40 - . (c) [4 marks] How does sodium chloride reacts with concentrated sulphuric acid? State the conditions for which the reaction can occur. [1 mark] (ii) Draw a simple diagram to show the layered structure of montmorillonite. [4 marks] Phg 10 27 (a) State the changes in acid-base properties of oxides of Period 3 elements. Explain the differences in their melting points in terms of structure and bonding. (c) [4 marks] Draw the possible structures of isomers of the following complexes. SiO2 and P4O6 are 2040oC.41 - . [6 marks] (ii) Describe the solubilities of the oxides in water and write balanced equations for the reaction of the oxides (if any) with water. 1610oC and 24oC respectively.STPM Chemistry (Semester 2) 26 (a) By referring to the physical and chemical properties of aluminium. SiO2. [2 marks] (iii) Explain how these cracks appear when the wet clay dries out. (b) [4 marks] Montmorillonite is a type of silicate clay which cracks during dry season. P4O6 (i) The melting points of Al2O3. [4 marks] (iii) Aluminium chloride is a white solid which fumes in moist air and sublimes at 180oC. describe the property of an aqueous solution of aluminium salt. explain (i) the reaction of anhydrous aluminium chloride with water. which is the stronger acid in aqueous solution? Explain your answer. from sodium to chlorine in the Periodic Table. [2 marks] . Write an equation to represent each typical property of the oxides. State the name of each isomer. (i) Draw the basic three dimensional structure of a silicate ion. (b) [6 marks] Between hydrogen chloride and hydrogen sulphide. [2 marks] (ii) why aluminium carbonate cannot be prepared from a solution containing Al3+ ions. (b) [5 marks] By writing equations for the reactions involved. (i) [Cr(NH3)4Cl2]+ (ii) [Cr(C2O4)3]3- [5 marks] Phg 11 28 (a) Oxides of the Period 3 elements include the following: Al2O3. (c) [4 marks] Suggest a use of each element or compound below. from carbon to lead. H has the empirical formula Co(Cl)x(NH3)y. Na3AlF6 by electrolysis.53 g of silver chloride is precipitated. 14. [2 marks] (iii) Both these complexes exhibit geometrical isomerism.52 g of H is reacted with excess AgNO3 solution. (b) [4 marks] How and why do CCl4 and SiCl4 differ in their reactions with water? Include in your answer any reactions that occur. The percentage by mass of cobalt. Suggest factors that have to be taken into consideration when choosing a site for an aluminium factory. (i) Silicon (ii) Silicon(IV) oxide (iii) Carbon dioxide (d) [3 marks] Aluminium is extracted from a mixture of molten aluminium oxide and cryolite. (b) [2 marks] A neutral compound. Cl = 42. (i) Explain what is meant by complex ion. Deduce the structural formula of the complex.42 - .00% .52% . Draw the transisomer for both of them. nitrogen and chlorine is as follow: Co = 23. N = 28.STPM Chemistry (Semester 2) 29 (a) Platinum(II) forms square planar complexes such as [Pt(NH3)2Cl2] while platinum(IV) forms octahedral complexes such as [Pt(NH3)4ClBr]2+. and explain how each of the uses is related to physical or chemical properties and structure. State one adverse effect on the environment as a result of the extraction process of aluminium. Explain if you expect H to be coloured. [4 marks] Trg -09 .53% When an aqueous solution containing 12. [9 marks] Phg 12 30 (a) Describe and explain the variation in boiling point of the tetrachlorides of Group 14 elements. [2 marks] (ii) Give the IUPAC name of [Pt(NH3)2Cl2] and [Pt(NH3)4ClBr]2+. Explain the observations.43 - . [7 marks] Sam tet 32 (a) State two different substances in everyday or industrial use that contain chlorine. [6 marks] (b) Explain the stability trend of the +2 and +3 oxidation states for the transition elements. construct the cycle and determine the lattice enthalpy of rubidium chloride.STPM Chemistry (Semester 2) 31 (a) White precipitate is formed when aqueous ammonia is added to aqueous magnesium chloride. RbCl can be determined indirectly using Born-Haber cycle. [6 marks] Trg 10 END OF QUESTIONS . (c) [4 marks] The lattice enthalpy of rubidium chloride. The white precipitate dissolves when excess ammonium chloride is added to the mixture. [3 marks] (c) What do you understand by the term transition element and explain why scandium and zinc are not transition elements. Given the data below. C8H18(l) and determine its value. (b) [4 marks] Given the following standard enthalpies of combustion: Hc of C(s) = −393 kJ mol-1 Hc of H2(g) = −285. Enthalpy change of formation of RbCl = −435 kJ mol-1 Enthalpy change of atomisation of Rb = +81 kJ mol-1 Enthalpy change of atomisation of Cl = +122 kJ mol-1 First ionization energy of Rb = +403 kJ mol-1 First electron affinity of Cl = −349 kJ mol-1 Explain why the lattice enthalpy of lithium chloride is more exothermic than that of rubidium chloride. For each of these substances. state its use and explain briefly how the use is related to the property of the substance.6 kJ mol-1 Hc of C8H18(l) = −5512 kJ mol-1 Define standard enthalpy of formation of octane. STPM Chemistry (Semester 2) .44 - .