ACJC_H2_CHEM_P1_Questions Prelim

© ACJC 2015 9647/01/Prelim/15 [Turn over 2 Section A For each question there are four possible answers, A, B, C, and D. Choose the one you consider to be correct. 1 Pure silicon required for microchips can be manufactured by heating silicon tetrachloride with zinc. 1.27 g of pure silicon could be obtained by heating 8.50 g of impure silicon tetrachloride with an excess of zinc. What is the percentage of impurity by mass in the sample of silicon tetrachloride? A 9.56 % B 14.9 % C 85.1 % D 90.4 % 2 Two elements M and N have the following properties:  M and N form ionic compounds K2M and K2N respectively.  Element N forms NF6 molecules whereas M is not able to do so. Which pair of electronic configurations of M and N is correct? M N A [He]2s22p2 [Ne]3s23p2 B [He]2s22p2 [Ne]3s23p4 C [He]2s22p4 [Ne]3s23p2 D [He]2s22p4 [Ne]3s23p4 3 In which of the following pairs does the first species have a larger bond angle than the second? A SO2, PI3 B SO3 2-, SO4 2- C H2S, NH3 D H2O, H3O+

© ACJC 2015 9647/01/Prelim/15 [Turn over 3 4 Which of the following statements is correct? A BCl3 and BrCl3 have the same molecular shape. B Cyclohexene and propanone are non–polar liquids. C LiAlH4 and NaBF4 contain dative covalent bonds. D XeF4 and H2C=C=CH2 are planar molecules. 5 In which of the following pairs does the first substance have a higher melting point than the second? First substance Second substance A CH3CH2OCH3 CH3CH2NHCH3 B CH3(CH2)4CH3 (CH3)2CHCH(CH3)2 C RbCl KCl D C O OH OH C O OH OH 6 Which of the following correctly shows the arrangement of the ions in decreasing order of ionic radius? A F– > O2– > N3– B Ca2+ > K+ > Cl- C S2– > Mg2+ > Na+ D Se2- > Br- > Ga3+

© ACJC 2015 9647/01/Prelim/15 [Turn over 4 7 Which graph correctly describes the behaviour of fixed masses of the ideal gases L and M where the number of moles of L is greater than number of moles of M? A B C D 8 A student dissolved 10.5 g of sodium fluoride in 250 g of water. The following data is obtained: Lattice energy of NaF −918 kJ mol-1 Enthalpy change of hydration of F- −457 kJ mol-1 Enthalpy change of hydration of Na+ −390 kJ mol-1 Given that the specific heat capacity of water is 4.2 J g-1 K-1, what would be the final temperature of the solution, if the initial temperature of water is 30 oC? A 6.5 °C B 13.1 oC C 16.9 oC D 46.9 oC

© ACJC 2015 9647/01/Prelim/15 [Turn over 5 9 Passing steam over hot coal produces combustible mixture of gases. H2O(g) + C(s) H2(g) + CO(g) ΔH = +131 kJ mol-1 In a certain mixture, the equilibrium partial pressures of steam and hydrogen gas are 90 kPa and 183 kPa respectively. What will be the new equilibrium partial pressure of hydrogen gas if the new equilibrium partial pressure of steam is increased to 150 kPa? A 100 kPa B 123 kPa C 236 kPa D