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 -