Edexcel Chemistry: Model Test Paper-10. Index Number

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1 Edexcel Chemistry: Model Test Paper-10 Chemistry: Unit 4 Index Number Name Advance Level Subject code: 6244 Time: 1 hour 30 min. Instruction to the candidates In the box above write your name and index number. Answer ALL the questions in the spaces provided in this question paper. Question number Leave blank Information for the candidates The total mark for this paper is 70. The marks, for individual questions and parts of questions are shown in round bracket. e.g. there are 1 pages in this question paper. All blank pages are indicated. Calculators may be used. Advice to the candidate You are reminded of the importance of clear and careful presentation in English in your answer. You are also reminded that you should take all usual safety precautions when working in a chemistry laboratory. Total 1. (a) When silver carbonate is heated, it decomposes into silver oxide and carbon dioxide. Ag 2 CO 3 (s) Ag 2 O(s) + CO 2 (g) At 227 C, the value of the equilibrium constant, K p, is 1.48 atm. (i) Write the expression for the equilibrium constant, K p. Edexcel-modelpaper-unit4-paper10 Jaydip.Chaudhuri 1

2 What is the pressure of carbon dioxide gas when silver carbonate is heated to a temperature of 227 C in a closed vessel? (b) When nitrosyl chloride, NOCl, is heated, it dissociates reversibly into nitric oxide, NO, and chlorine, Cl 2, according to the equation 2NOCl(g) 2NO(g) + Cl 2 (g) H = kj mol 1 (i) Write the expression for the equilibrium constant, K p, for this reaction mol of nitrosyl chloride was placed in a sealed container and heated to 500 C. Equilibrium was reached when 22.0% of the nitrosyl chloride had dissociated. The pressure in the vessel was 5.00 atm. Calculate the value of K p at this temperature, stating its units. (iii) State the effect of an increase in temperature on the value of the equilibrium constant, K p. Justify your answer. (5) Edexcel-modelpaper-unit4-paper10 Jaydip.Chaudhuri 2

3 (iv) Hence suggest in which direction the position of equilibrium moves when the temperature is increased. Justify your answer. (Total 12 marks) 2. (a) Electron affinities of an element, such as iodine, can be calculated using a Born-Haber cycle. Value / kj mol 1 Enthalpy of atomisation of calcium, H a (calcium) st ionisation energy of calcium, IE nd ionisation energy of calcium, IE Enthalpy of atomisation of iodine, H a (iodine) +107 Lattice energy of calcium iodide, H latt 2074 Enthalpy of formation of calcium iodide, H f 534 (i) Define the term first electron affinity, EA 1. Write suitable symbols or values in the boxes to label the Born-Haber cycle below. Edexcel-modelpaper-unit4-paper10 Jaydip.Chaudhuri 3

4 (iii) Use the data to calculate the first electron affinity of iodine, EA 1. (b) The values of the lattice energies of potassium iodide and calcium iodide experimentally determined from Born-Haber cycles and theoretically calculated from an ionic model are shown below. Experimental lattice energy /kj mol 1 Theoretical lattice energy /kj mol 1 Potassium iodide, KI(s) Calcium iodide, CaI 2 (s) (i) Explain why the experimental lattice energy of potassium iodide is less exothermic than the experimental lattice energy of calcium iodide. Edexcel-modelpaper-unit4-paper10 Jaydip.Chaudhuri 4

5 Explain why the experimental and theoretical values of the lattice energy are almost the same for potassium iodide, but are significantly different for calcium iodide. (Total 13 marks) 3. (a) (i) State the type of bonding in: magnesium oxide, MgO... sulphur dioxide, SO 2... When water is added to magnesium oxide, a solution of ph 11 is formed. When sulphur dioxide is bubbled into water a solution of ph 2 is formed. Write the equation for each reaction and explain why each solution is not neutral. Magnesium oxide + water Edexcel-modelpaper-unit4-paper10 Jaydip.Chaudhuri 5

6 Sulphur dioxide + water (iii) Explain why silicon dioxide does not react with water. (4) (b) Hydrated aluminium chloride, which is ionic, and silicon tetrachloride, which is covalent, both form acidic solutions in water. (i) Write an ionic equation for the reaction of hydrated aluminium ions with water. Write an equation for the reaction of silicon tetrachloride with water. (c) (i) Tin(IV) chloride is stable to heat, but lead(iv) chloride decomposes at room temperature to lead(ii) chloride and chlorine. What trend in Group 4 does this illustrate? Suggest how, if at all, tin(ii) chloride and lead(ii) chloride would react with a solution containing Fe 3+ ions. Tin(II) chloride Edexcel-modelpaper-unit4-paper10 Jaydip.Chaudhuri 6

7 Lead (II) chloride (Total 15 marks) 4. This question concerns the equilibrium 2NO(g) N 2 (g) + O 2 (g) H = 180 kj mol 1 (a) Define the term partial pressure (b) (i) Write the expression for K p for the above reaction. At 1600 C and 1.5 atm pressure NO is 99 % dissociated at equilibrium. Calculate the value of K p under these conditions. (4) Edexcel-modelpaper-unit4-paper10 Jaydip.Chaudhuri 7

8 (c) State and explain the effect on K p and hence on the position of equilibrium of decreasing the temperature at constant pressure (d) The reaction Ni(s) + 4CO(g) Ni(CO) 4 (g) is used to purify nickel. (i) Write the expression for K p for this system. In order to achieve a high equilibrium yield of Ni(CO) 4 should a low or a high partial pressure of carbon monoxide be used? Explain your answer in terms of K p (Total 12 marks) 5. (a) (i) Define the term enthalpy of atomisation (iii)... Write the equation, with state symbols, which represents the change occurring when the enthalpy of atomisation of chlorine is measured.... Draw a Born-Haber cycle and use it to determine the lattice energy of strontium chloride, SrCl 2 (s), using the following data: Edexcel-modelpaper-unit4-paper10 Jaydip.Chaudhuri 8

9 Enthalpy change/ kj mol 1 enthalpy of formation of SrCI 2 (S) 829 enthalpy of atomisation of strontium +164 enthalpy of atomisation of chlorine st ionisation energy of strontium nd ionisation energy of strontium electron affinity of chlorine 349 (b) In fireworks, the thermal decomposition of strontium(ii) chloride, SrCI 2, gives the covalent molecule of strontium(i) chloride, SrCI(g), which is responsible for the red colour of the fireworks. SrCl 2 (s) SrCl(g) + Cl(g) H = +737 kj mol 1 (5) (i) Calculate the enthalpy of formation of SrCI(g) using the H. given above, the enthalpy of formation of SrCl 2 (s) ( 829 kj mol 1 ) and the enthalpy of atomisation of chlorine (+122 kj mol 1 ). Explain what would be the effect of a lowering in the temperature of the exploding firework on the value of the equilibrium constant and on the position of this equilibrium Edexcel-modelpaper-unit4-paper10 Jaydip.Chaudhuri 9

10 (iii)... Some solid SrCI 2 was heated at 1500 C and equilibrium was reached. The total pressure of the gases produced was found to be 4.2 atm. Write the expression for K p and calculate its value with units. (5) (Total 18 marks) Edexcel-modelpaper-unit4-paper10 Jaydip.Chaudhuri 10

11 Edexcel-modelpaper-unit4-paper10 Jaydip.Chaudhuri Li Na K Rb Cs Fr (223) (226) (227) (261) (262) (263) 55 (99) (231) (147) (237) 150 (242) 152 (243) 157 (247) 159 (245) 163 (251) 165 (254) 167 (253) 169 (256) 173 (254) 175 (257) (210) (210) (222) Lithium Sodium Potassium Rubidium Caesium Francium Berylium Magnesium Calcium Strontium Barium Radium Scandium Yttrium Lanthanum Actinium Titanium Zirconium Hafnium Unnilquadium Vanadium Niobium Tantalum Unnilpentium Chromium Molybdenum Tungsten Unnilhexium Manganese Technetium Rhenium Cerium Thorium Praseodymium Protactinium Neodimium Uranium Promethium Neptunium Samarium Plutonium Europium Americium Gadolinium Curium Terbium Berkelium Dysprosium Californium Holmium Einsteinium Erbium Fermium Thulium Mendelevium Ytterbium Nobelium Lutetium Lawrencium Iron Ruthenium Osmium Cobalt Rhodium Iridium Nickel Palladium Platinum Copper Silver Gold Zinc Cadmium Mercury Boron Aluminium Gallium Indium Thallium Carbon Silicon Germanium Tin Lead Nitrogen Phosphorus Arsenic Antimony Bismuth Oxygen Sulphur Selenium Tellurium Polonium Fluorine Chlorine Bromine Iodine Astatine Neon Argon Krypton Xenon Radon Helium Hydrogen H Be Mg Ca Sr Ba Ra Sc Y La Ac Ti Zr Hf Unq V Nb Ta Unp Cr Mo W Unh Mn Tc Re Ce Th Pr Pa Nd U Pm Np Sm Pu Eu Am Gd Cm Tb Bk Dy Cf Ho Es Er Fm Tm Md Yb No Lu Lr Fe Ru Os Co Rh Ir Ni Pd Pt Cu Ag Au Zn Cd Hg B Al Ga In Ti C Si Ge Sn Pb N P As Sb Bi O S Se Te Po F Cl Br I At Ne Ar Kr Xe Rn He Atomic Number Symbol Name Molar mass in g mol 1 Period Key Group THE PERIODIC TABLE Lanthanide elements Actinide elements