RI Prelim CHEM P1

-1- RAFFLES INSTITUTION (JUNIOR COLLEGE) PRELIMINARY EXAMINATION 2009 HIGHER 2 CHEMISTRY 9746/01 Paper 1 Multiple Choice 24 September 2009 1 hour Additional Materials: Multiple Choice Answer Sheet Data Booklet READ THESE INSTRUCTIONS FIRST Do not open this question booklet until you are told to do so. Write in soft pencil. Do not use staples, paper clips, highlighters, glue or correction fluid. Write your name, class and index number in the spaces provided on the Answer Sheet. There are forty 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 to be correct and record your choice with a soft pencil on the separate Answer Sheet. Read the instructions on the Answer Sheet very carefully. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. This document consists of 16 printed pages.

-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 The following reaction is used in the titration of iron( II ) solution with acidified potassium dichromate( VI ). 6Fe 2+ + Cr 2O7 2– + 14H + → 6Fe 3+ + 2Cr 3+ + 7H 2O If 50.0 cm 3 of an iron( II ) solution require 45.20 cm 3 of 0.100 mol dm – 3 potassium dichromate( VI ) for reaction, what is the mass of Fe 2+ ions in 1 dm 3 of the iron( II ) solution? A 12.6 g B 25.2 g C 30.3 g D 60.5 g 2 Of the following, which is the strongest oxidising agent? A O 2 + B O 2 C O 2 – D O2 2– 3 Which of the following equations represents the th ird ionisation energy of titanium? A Ti(s) → Ti 3+ (g) + 3e – B 3Ti(g) → 3Ti +(g) + 3e – C Ti 2+ (g) → Ti 3+ (g) + e – D 3Ti 2+ (g) → 3Ti 3+ (g) + 3e – 4 Which form of orbital hybridisation can form molec ules or ions that are square pyramidal in shape? A sp 2 B sp 3 C sp 3d D sp 3d2 [Turn over

-3- 5 Which one of the following pairs does not contain two species with the same molecular shape? A SC l 2 and SO 2 B BC l3 and BrC l3 C BeF 2 and BrF 2 – D C lF4 + and PF 4 – 6 The standard enthalpy changes for three reactions are given below. C(s) + 2H 2(g) → CH 4(g) ∆ H/ring2 = x C(s) + O 2(g) → CO 2(g) ∆ H/ring2 = y H 2(g) + ½O 2(g) → H 2O( l) ∆ H/ring2 = z What is the standard enthalpy change for the react ion CH 4(g) + 2O 2(g) → CO 2(g) + 2H 2O( l)? A x + y – z B z + y – 2x C 2z + y – x D 2z + y – 2x 7 Graphite and diamond are two allotropes of carbon. Although graphite is thermodynamically more stable than diamond at 25 °C and 1 atm, a piece of diamond will not transform into graphite, even over a period of one million years. Which of the following correctly explains this observation? A ∆ G for the reaction diamond → graphite is greater than zero. B ∆ H for the reaction diamond → graphite is greater than zero. C The reverse reaction graphite → diamond proceeds quickly. D The reaction diamond → graphite has a large activation energy. [Turn over

-4- 8 The rate of the reaction between substances A and B is found to follow the rate law rate = k [A] m [B] where k is the rate constant and has units of mol – 2 dm 6 s – 1. Two experiments to study the kinetics of this reac tion were carried out and the data obtained are tabulated below. Experiment Initial [A] / mol dm – 3 Initial [B] / mol dm – 3 Initial rate / mol dm – 3 s – 1 1 0.040 0.080 R 2 0.020 y ½ R What is the value of y in Experiment 2? A 0.020 B 0.040 C 0.160 D 0.320 9 The dissociation of dinitrogen tetroxide into nitr ogen dioxide is represented by the equation below. N 2O4(g) ⇋ 2NO 2(g); ∆ H = +52.7 kJ mol – 1 If the temperature of an equilibrium mixture of th ese gases is increased at constant pressure, the volume of the mixture will A decrease, because a shift in position of equilibri um towards the left would more than counteract any thermal expansion. B decrease, because a shift in position of equilibri um towards the left would also produce cooling and hence thermal contraction. C increase, but only because of a shift in position of equilibrium towards the right. D increase, both because of a shift in position of e quilibrium towards the right and because of thermal expansion. [Turn over

-5- 10 Two gases, X2 and Y, react as follows: X2(g) + 3 Y(g) ⇋ X2Y3(g) A mixture containing 0.50 mol of X 2 and 0.50 mol of Y was heated in a 0.50 dm 3 closed container. When the reaction reached equilibrium, 0.10 mol of X2Y3 was produced. What is the value of the equilibrium constant, Kc, for this reaction? A 0.98 B 1.25 C 3.91 D 31.2 11 The numerical values of the solubility products at 25 °C for AgC l and Ag I are 1.6 × 10 – 10 and 8.0 × 10 – 17 respectively. What is the equilibrium constant for the reaction below? AgC l(s) + I– (aq) ⇋ Ag I(s) + C l– (aq) A 1.3 × 10 – 26 B 5.0 × 10 – 7 C 2.0 × 10 6 D 1.3 × 10 16 12 The graph shows the change in pH when 0.10 mol dm – 3 acid is gradually added to V cm 3 of 0.10 mol dm – 3 alkali. Which one of the following combinations could have given these results? V Alkali Acid A 10 Ba(OH) 2 CH 3CO 2H B 20 Sr(OH) 2 HC l C 10 Ca(OH) 2 H 2SO 4 D 20 NaOH HO 2C− CO 2H [Turn over

-6- 13 Use of the Data Booklet is relevant to this question. A student connects a Cu 2+ /Cu half-cell to a Ag +/Ag half-cell. The salt bridge contains aqueous Na 2SO 4. The voltage measured across the electrodes is found to be +0.42 V. Which of the following could be a reason for the d iscrepancy between the calculated E o cell and the observed value of +0.42 V? A The piece of copper in the Cu 2+ /Cu half-cell was too small. B The piece of silver in the Ag +/Ag half-cell was too large. C The concentration of Cu 2+ was larger than 1 mol dm – 3. D The concentration of Ag + was larger than 1 mol dm – 3. 14 Consecutive elements A, B and C are in Period 3 of the Periodic Table. B has the highest first ionisation energy and the lowest melting point among the three elements. What could be the identities of A, B and C? A sodium, magnesium, aluminium B magnesium, aluminium, silicon C aluminium, silicon, phosphorus D silicon, phosphorus, sulfur 15 Two solutions were prepared by dissolving a chlori de and an oxide of the elements in the third period of the Periodic Table in separate portions of water. Both solutions prepared can be used to dissolve A l2O3 but only one can be used to dissolve SiO 2. Which of the following could be the chloride and t he oxide used? A NaC l and SO 3 B PC l5 and Na 2O C MgC l2 and MgO D SiC l4 and P 4O10 [Turn over

-7- 16 P, Q and R are Group II elements. They form compounds with the following properties: • P(NO 3)2 has a higher thermal decomposition temperature tha n R(NO 3)2. • RCO 3 has a more endothermic enthalpy change of decomposition th