VJC H2 Chem 2013 Prelim P1 QP & Soln

2  VJC 2013 9647/01/13 Section A For each question there are four possible answers, A, B, C, and D. Choose the one you consider to be correct. 1 25.0 cm 3 of a solution of hydrogen peroxide, H 2O2, was oxidised by excess potassium manganate(VII) solution under acidic condition. The volume of oxygen gas produced at room temperature and pressure was 26 cm3. What is the concentration of hydrogen peroxide in the solution? A 2.89 x 10 –2 mol dm–3 C 8.66 x 10–2 mol dm–3 B 4.33 x 10–2 mol dm–3 D 1.30 x 10–1 mol dm–3 2 The equations for three reactions are given below. Cl 2 + 2I–  2Cl– + I2 2Fe3+ + 2I–  2Fe2+ + I2 Cl2 + 2Fe2+  2Cl– + 2Fe3+ What is the correct order of strength of Cl –, Fe2+ and I– as reducing agents? weakest  strongest A Cl– I– Fe 2+ B Cl– Fe2+ I– C Fe2+ I– Cl– D I– Cl– Fe 2+ 3 In which one of the following pairs does the first species have a higher first ionisation energy than the second one? A Sb, Te B Kr, Ar C Mg +, Al+ D Se, Se+ 4 The use of the Data Booklet is relevant to this question. Consider the following chlorine–containing species: ICl 2 , ClF3, ClO3  Which one of the following statements is incorrect? A Not all atoms achieve stable octet configuration. B ICl2  is linear, ClF3 is T–shaped while ClO3  is trigonal pyramidal. C The bond angles increase in the order of ClF3, ClO3  , ICl2 . D The oxidising power decreases in the order of O2, F2, Cl2, I2. 1473

3  VJC 2013 9647/01/13 [Turn Over 5 Refer to the molecule below: Which one of the following shows the correct information with regard to the various labeled bond angles? smallest bond angle  largest bond angle A c d e B d a c C e b a D b e d 6 A graph of  / p versus p is obtained for a real gas Z at 273 K. [ = density of gas in g dm3, p = pressure of gas in Pa] What is the relative molecular mass of Z at 273 K? A 273RY B R 273Y C YR 273 D Y R 273 7 Which one of the following equations represents a reaction that is feasible at all temperatures? A W(s)  X(s) + Y(g) H > 0 B 2T(g) + 3U(g)  4V(g) H < 0 C R(g)  2Q(g) H < 0 D K(g) + L(g) → M(g) H > 0 p  / p 0 Y a b c e d 1474

4  VJC 2013 9647/01/13 8 The rate of the reaction 3D(g) + E(g)  G(g) is given by the rate equation, rate = k [D]2[E]. Two experiments using the same initial amounts of D and E were carried out at temperature, T. The data is shown below. experiment volume of reaction vessel initial rate of reaction 1 V R 1 2 2V R2 Which one of the following shows the correct relationship between R 1 and R2? A R2 = 8 1 R1 B R2 = 4 1R1 C R2 = R1 D R2 = 8R1 9 Gas A decomposes to two other gases, B and C, according to the following equation: 2A(g) 3 B(g) + C(g) The graph below shows the decomposition of 1.0 mol of pure gas A in the presence of a catalyst at various temperatures. Which one of the following statements about the above system is incorrect? A The decomposition of A is endothermic. B The Kp of the system decreases with increasing temperature. C The percentage decomposition of A is 60 % at 300 oC. D The system becomes more disordered when it reaches equilibrium state. 1.0 0.8 moles of A remaining time 300 oC 0.6 0.4 0.2 0.0 250 oC 200 oC 1475

5  VJC 2013 9647/01/13 [Turn Over 10 The equilibrium constant for the following reaction is less than 1. HPO4 2(aq) + H2BO3 (aq) H2PO4 (aq) + HBO3 2(aq) Which one the following gives the correct relative strengths of the acids and bases in the reaction? acids bases A H2PO4  > H 2BO3  and HBO 3 2 > HPO 4 2 B H2BO3  > H 2PO4  and HBO 3 2 > HPO 4 2 C H2PO4  > H 2BO3  and HPO 4 2 > HBO 3 2 D H2BO3  > H 2PO4  and HPO 4 2- > HBO 3 2 11 The solubility products of three calcium salts are shown below: calcium salt CaCO 3 CaF 2 Ca 3(PO4)2 Ksp 8.7 x 109 4.0 x 1011 1.2 x 1026 Calcium nitrate is gradually added to a 1 dm 3 solution containing carbonate, fluoride and phosphate ions, each with a concentration of 1.0 x 103 mol dm–3. What is the correct order at which these calcium salts precipitate out of solution? A Ca 3(PO4)2, CaF2, CaCO3 B Ca3(PO4)2, CaCO3, CaF2 C CaCO3, CaF2, Ca3(PO4)2 D CaF2, CaCO3, Ca3(PO4)2 12 Besides the standard hydrogen electrode, other standard electrodes such as the calomel electrode may be used to determine the standard reduction potential of half cells. The calomel electrode has a standard reduction potential of +0.24 V when connected to a standard hydrogen electrode. What is the voltmeter reading when a Cu 2+|Cu half cell is connected to a standard calomel electrode under standard conditions? A –0.48 V C +0.10 V B –0.10 V D +0.48 V 1476

6  VJC 2013 9647/01/13 13 X, Y and Z are elements in the same period of the Periodic Table. Given the following information:  The hydroxide of X gives an aqueous solution with pH less than 7.  The hydroxide of Y reacts with both strong acids and alkalis.  The hydroxide of Z gives an aqueous solution which is strongly alkaline. Which one of the following statements is correct? A The atomic radius decreases from X to Y to Z. B The electrical conductivity decreases from X to Y to Z. C The electronegativity decreases from X to Y to Z. D The first ionisation energy increases from X to Y to Z. 14 CaCO 3 decomposes at 900 C to produce CO2 and the metal oxide. CaSO4 decomposes at 1100 C to produce SO3 and the metal oxide. Which one of the following statements explains the greater thermal stability of CaSO4? A The CO2 molecule is smaller than SO3. B The CO3 2– ions are more easily polarized than SO4 2–. C The charge density of CO3 2– is greater than that of SO4 2–. D The lattice energy of CaCO3 is more exothermic than CaSO4. 15 Astatine, At is below iodine in Group VII of the Periodic Table. Which one of the following statements is most likely to be true for astatine? A At 2 is soluble in water. B AgAt is insoluble in dilute NH3 but dissolves in concentrated NH3. C HAt decomposes readily on heating to give hydrogen and astatine. D At2 reacts with aqueous NaCl to give an aqueous solution of NaAt and Cl2. 16 The use of the Data Booklet is relevant to this question. x mol of bromine gas is reacted completely with excess aqueous sodium hydroxide at 70 C. The resulting solution is acidified and aqueous silver nitrate added. What is the mass (in g) of silver bromide formed? A 113x C 313x B 188x D 376x 1477

7  VJC 2013 9647/01/13 [Turn Over 17 [CoP6]3+, [CoQ6]3+ and [CoR 6]3+ are three complexes of cobalt(III). Ligand P results in a smaller d–d splitting compared to ligand Q while [CoR6]3+ is blue in colour. Which one of the following diagrams shows the possible absorption spectra of the three cobalt(III) complexes? A B C D [CoP6]3+ [CoR6]3+ [CoQ6]3+ absorbance wavelength /nm 400 500 600 700 800300 [CoQ6]3+ [CoR6]3+ [CoP6]3+ absorbance wavelength /nm 400 500 600 700 800300 [CoR6]3+ [CoQ6]3+ [CoP6]3+ absorbance wavelength /nm 400 500 600 700 800300 [CoR6]3+ [CoP6]3+ [CoQ6]3+ absorbance wavelength /nm 400 500 600 700 800300