TJC H2 Chem 2013 Prelim P1 QP & Soln

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2   9647/01/TJC Prelim 2013 [Turn Over  Section A For each question there are four possible answers, A, B, C and D. Choose the one you consider to be correct. 1 In which pair do both atoms have the same number of unpaired electron in their ground states? A Ca, Ni B Na, Sc C N, Fe D Fe, Cr 2 Silicon, phosphorus and sulfur are in Period 3. Which of the following statements best explains why silicon   (1s 2 2s 2 2p 6 3s2 3p2) has a lower first ionisation energy than phosphorus (1s2 2s2 2p6 3s2 3p3)? A Silicon has fewer electrons than phosphorus. B The 3p electrons of phosphorus do not experience inter-electronic repulsion. C The 3p electrons of phosphorus are further away from the nucleus. D Phosphorus has more protons than silicon. 3 Comproportionation is a chemical reaction where two reactants, each containing the same element but with a different oxidation number, form a product in which the element involved reaches the same oxidation number in the product. 1 mol of potassium iodide undergoes comproportionation with compound X to form 0.6 mol of iodine. What could be the identity of compound X? A KIO2 B IO2 C KIO3 D KIO4 4 A pure hydrocarbon was completely isolated from a fractional distillation column in a refinery. When 10 cm3 of the hydrocarbon was burned in excess oxygen, the volume of the mixture decreased by 30 cm 3. On passing the resultant mixture through a solution of sodium hydroxide, the volume further decreased by 30 cm 3. All volumes were measured at room temperature and pressure. What is the formula of the hydrocarbon? A C2H6 B C3H6 C C3H8 D C4H10 1312

3   9647/01/TJC Prelim 2013