SAJC H1 CHEM Prelims Paper 1 Questions + Solutions

ST ANDREW'S JUNIOR COLLEGE JC2 Preliminary Examinations CHEMISTRY 8872/01 Higher 1 11 September 2008 Paper 1 50 minutes Additional materials: Data Booklet, Multiple Choice Answer Sheet INSTRUCTIONS TO CANDIDATES There are thirty questions on this paper. Answer all questions. For each question, there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate answer sheet. This question paper consists of 13 printed pages including this page 1

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Section A Answer all questions 1. Which statement about relative atomic mass is correct? A It is measured in grams. B It is a ratio of masses. C It is the number of atoms in a molecule. D It is the same as the mass of 1 mol of atoms. 2. 10 cm 3 of a hydrocarbon CxHy was exploded with an excess of oxygen. There was a contraction of 30 cm3. When the product was treated with a solution of potassium hydroxide, there was a further contraction of 40 cm3. What is the molecular formula of the hydrocarbon? [All gas volumes are measured at r.t.p.] A C 4H8 B C4H10 C C3H6 D C3H8 3. Nitrogen dioxide reacts with iodide ions under acidic conditions according to the following equation, NO 2 + 2I- + 2H+ Æ NO + I2 + H2O How many moles of electrons are gained by one mole of nitrogen dioxide? A 1 B 2 C 3 D 4 [Turn Over 3

4. Which species is formed when bromine molecule undergoes reduction? A HBrO B NaBrO3 C HBrO4 D BBr3 5. Which of the following particles, on gaining an electron have a half-filled set of p orbitals? A P B N ─ C O2+ D Si+ 6. L and M are elements with the following successive ionization energies in kJ mol-1. L 557 1921 2714 11410 13120 16723 19116 M 905 2245 3231 4803 7911 9300 18600 L and M are likely to form a compound of formula A L3M2 B L2M3 C LM4 D L4M 7. Which of the following molecules is not planar? A BeCl2 B XeF4 C SO2 D SiCl4 [Turn Over 4

8. NH 3 boils at -33.3 °C while PH3 boils at -87.8 °C. Which of the following best explains the difference in boiling points of NH3 and PH3? A PH3 is non-polar whereas NH3 is polar. B The strength of Van der Waals’ forces is weaker in PH3 than in NH3. C Van der Waals’ forces are present in PH3 whereas hydrogen bonding is present in NH3. D The P—H bond is weaker than the N—H bond. 9. Given the standard enthalpy change of formation of Fe 3O4 (s) and Al2O3 (s) is -1117.1 kJ mol-1 and -1669.8 kJ mol-1 respectively, what is the standard enthalpy change of reaction for the following reaction? 3 Fe3O4 (s) + 8 Al (s) Æ 9 Fe (s) + 4 Al2O3 (s) A +3327.9 kJ mol-1 B -3327.9 kJ mol-1 C -1109.3 kJ mol-1 D - 552.7 kJ mol-1 10. 5 x 10-4 mole of butane was burnt to heat up 100 g of water at room temperature and pressure. Assuming that there was negligible heat loss to the surroundings, calculate the final temperature of the water. Given: Standard enthalpy change of combustion of butane = – 2877.5 kJ mol-1 Specific heat capacity of water = 4.2 J K-1 cm-3 A 28.4 °C B 33.4 °C C 61.6 °C D 86.6 °C [Turn Over 5

11. Pepsin is a digestive enzyme found in gastric juice that aids in the digestion of proteins. The graph below shows how the rate of a reaction varies with the protein (reactant) concentration for pepsin enzyme. [protein] rate of reaction Which of the following can be deduced from the graph above? A The rate is first order at low protein concentration and zero order at high protein concentration. B Increasing the protein concentration will increase the rate of reaction. C The rate is second order at low protein concentration and zero order at high protein concentration. D The enzyme is unable to function at high protein concentrations. 12. The data in the table below refer to the reaction between acidified iodate (V) ions and iodide ions solution. IO3 - (aq) + 5I- (aq) + 6H+ (aq) 3I2 (aq) + 3H2O (l) Volume / cm3 Experiment IO3 - (aq) I- (aq) H+ (aq) Water Relative initial rate 1 10 50 60 80 1.0 2 20 50 60 70 2.0 3 10 25 60 105 0.5 4 10 50 120 20 4.0 What is the rate equation for the reaction? A rate = k [IO 3 -] [I-]5 [H+]6 B rate = k [IO3 -] [I-] C rate = k [IO3 -] [I-]2 [H+]2 D rate = k [IO3 -] [I-] [H+]2 [Turn Over 6

13. Which of the following is incorrect for the following imposed changes at equilibrium for this reaction? 2P (g) + Q (g) 3R (g) ΔH < 0 Imposed changes Position of equilibrium Forward rate at new equilibrium Backward rate at new equilibrium A Increase total pressure by compression No change Increase Increase B Increase temperature Shifts left Increase Increase C Adding catalyst No change Increase Increase D Adding more R Shifts left Increase Decrease 14. In the mixture containing 0.80 mol of CO and 1.30 mol of H2O, the reaction occurs according to the equation below. CO (g) + H 2O (g) CO 2 (g) + H2 (g) At equilibrium, 0.35 mol of CO2 was present. What is the equilibrium constant, Kc, at the temperature of this experiment? A 3.49 B 0.82 C 0.29 D 1.22 15. What is the final pH of a solution formed by mixing equal volumes of two separate solutions of pH 3.0 and pH 5.0? A 3.0 B 3.3 C 4.0 D 4.3 [Turn Over 7

16. Which of the following solutions can be used to give an effective buffer solution at pH > 7? A C6H5COOH and C6H5COOK B H3PO4 and Na3PO4 C KOH and KNO3 D CH3NH2 and CH3NH3Cl 17. Which of the following is unlikely to dissolve in dilute hydrochloric acid? A Na2O B MgO C Al2O3 D SiO2 18. Consider the sequence of chlorides NaCl, SiCl 4 and PCl3. Which of the following properties increases from NaCl to PCl3? A Melting point B Covalent character C pH of the resultant solution when mixed with water D electrical conductivity of the chloride in liquid state [Turn Over 8

19. A compound has the following properties: ƒ It reacts with phosphorus pentachloride, giving off white fumes of HC l. ƒ It reacts with aqueous bromine. ƒ It reacts with ethanol ƒ It reacts with sodium hydroxide to form an ionic compound. The compound is A CH3CH=CHCOOH B CH3CH=CHCH2OH C CH3CH=CHCHO D CH3CH2CH2COOH 20. How many isomers are possible for the unsaturated compound of molecular formula C 3H5F? A 3 B 4 C 5 D 6 21. Which of the following reagents will distinguish between compounds S and T? H3C O OH H3C O OH S T A Aqueous bromine B Alkaline aqueous iodine C Acidified potassium dichromate (VI) D 2,4 dinitrophenylhydrazine [Turn Over 9

22. Why does the reaction of CH3CH2CH2X + OH- Æ CH3CH2CH2OH + X- take place more readily when X is Br than when X is F? A The C-F bond is more polar than the C-Br bond B The C-F bond is stronger than the C-Br bond C The C-F bond is longer than the C-Br bond D The Br- ion is a stronger nucleophile than the F- ion. 23. The process of cracking produces useful substances from crude oil. Which of the following represents a possible reaction for cracking? A CH 3(CH2)10CH3 Æ CH3(CH2)3CH3 + CH3CH=CH2 B CH3(CH2)11CH3 Æ CH3(CH2)3CH3 + 2 CH3CH=CH2 C CH3(CH2)12CH3 Æ CH3(CH2)3CH3 + 3 CH3CH=CH2 D CH3(CH2)13CH3 Æ CH3(CH2)3CH3 + 4 CH3CH=CH2 24. Vitamin B5, also called pantothenic acid, is one of the eight water soluble B vitamins. Vitamin B5 is critical to the manufacture of red blood cells and sex related hormones produced in the adrenal glands. The structure of Vitamin B5 is as shown below. CHO C C H H