TPJC H2 Chem 2012 Prelim P1 QP

2 TPJC_2012_9647_P1 Section A For each question, there are four possible answers, A, B, C, and D. Choose the one you consider to be correct. 1. Which molecule has six bonding electrons? A C2H4 C H2S B CO2 D NCl3 2. Which of the following ions has the smallest ionic radius? A F − C Na + B Mg 2+ D Al 3+ 3. Consider the following half-equations. Fe 2+ → Fe 3+ + e C2O4 2– → 2CO2 + 2e What volume of 0.01 mol dm-3 K2Cr2O7 is required to oxidise 20 cm3 of an acidified solution of 0.01 mol dm-3 FeC2O4? A 10 cm3 C 30 cm3 B 20 cm3 D 40 cm3

3 TPJC_2012_9647_P1 4. Which one of the following graphs below shows the correct plot of pV against p for a fixed mass of ideal gas at two temperatures, T1 and T2, in which T1 > T2? 5. A student used the apparatus below to determine the enthalpy change of combustion of propan-1-ol. The following results were obtained: mass of propan-1-ol burnt = 0.60 g mass of water heated = 200 g initial temperature of water = 21.00C Given that the enthalpy change of combustion propan-1-ol is −2021 kJ mol−1 and the heat capacity of water is 4.17 J K−1 g−1, what would be the final temperature of the water? A 24.2 oC C 29.1 oC B 45.2 oC D 48.4 oC

4 TPJC_2012_9647_P1 6. The radius and charge of each of six ions are shown below: The ionic solids AX, BY and CZ are of the same lattice type. What is the correct order of their lattice energies placing the one with the highest numerical value first? A CZ > AX > BY C CZ > BY > AX B AX > CZ > BY D AX > BY > CZ 7. The table below shows the standard thermodynamic values for the synthesis of hydrogen chloride: H2 (g) + Cl2 (g) → 2HCl (g). ∆Hɵ -184.6 kJ mol-1 ∆Sɵ +0.02 kJ K-1 mol-1 From the data, what is the value of ∆Gɵ? A +178.6 kJ mol-1 C -185.1 kJ mol-1 B -178.6 kJ mol-1 D -190.6 kJ mol-1 8. How would the magnitude of the following vary down Group II? (i) the standard electrode potential of M 2+ (aq)/ M(s) electrode, Eo , (ii) the lattice energy of the oxide, ∆Ho latt, (iii) the standard enthalpy change of hydration of M 2+ (g), ∆Ho hyd.

5 TPJC_2012_9647_P1 9. The mechanism for a certain reaction is given below: 2A C (fast) C + B  D (slow) D + B  A2B2 (fast) What conclusion can be drawn from the above mechanism? A The rate equation is rate = k[C][B]. B The units of the rate constant, k, is mol-2 dm6 s-1. C The reaction is first order with respect to D. D The overall equation is 2A + 2B + C + D  A2B2. 10. The diagrams P, Q, R and S show how a change in conditions affects the Maxwell- Boltzmann distribution of molecular energies for gas G. In each case, the original distribution is shown by a solid line and the distribution after a change has been made is shown by a dashed line. Which one of the following statements is correct? A the change shown in diagram Q occurs