SAJC_H2_CHEM_P1_QNS Prelim

1 [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. A solid hydrocarbon was completely combusted in a closed vessel at 120 oC. The residual gas had a volume of 64 cm 3, which decreased by 24 cm 3 after bubbling through a dehydrating agent. After this, 40% of the final gas volume consisted of oxygen. What is the empirical formula of the hydrocarbon? A CH B CH2 C CH3 D C2H3 2. When cobalt metal is reacted with a solution containing cobalt( III) ions, cobalt( II) ions are formed. How many moles of Co and Co 3+(aq) would result in a mixture containing both cobalt(II) and cobalt(III) ions in the mole ratio of 3:1 after the reaction had taken place? Moles of Co Moles of Co3+ A 1 2 B 1 3 C 1 5 D 2 3 3. Which graph does not share the same general shape with the other three graphs according to the ideal gas law for a fixed mass of gas? A pV against p (at constant T) B V/T against T (at constant p) C p against V (at constant T) D pV against V (at constant T)

2 [Turn Over 4. Which element will possess an empty s orbital after forming a singly-charged cation? A Barium B Vanadium C Copper D Gallium 5. Which of the following reactions will form a product with the same shape as the reactant with respect to the underlined element? A 2AlCl3  Al2Cl6 B 2H2O2  2H2O + O2 C PCl3 + Cl2  PCl5 D CH3CH2CHO + [O]  CH3CH2COOH 6. Which of the following is arranged correctly in the order of decreasing melting points? A Sulfur > Chlorine > Argon B Carbon dioxide > Silicon dioxide > Germanium dioxide C Beryllium chloride > Magnesium chloride > Calcium chloride D Sodium > Magnesium > Aluminium

3 [Turn Over 7. A student dissolved 0.238 mol of sodium fluoride in 300 cm3 of water. Given the following data: 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 What would be the initial temperature of the water if the final temperature of the solution is 20.00 o C? Assume that the specific heat capacity of sodium fluoride solution is 4.18 J g −1 K −1 . A 6.52 o C B 13.48 o C C 20.00 o C D 33.48 o C 8. Ammonia gas and hydrogen chloride gas react to form ammonium chloride as shown in the equation below: NH3 (g) + HCl (g) → NH4Cl (s) ΔHo = −176 kJ mol−1 The standard entropy change of this reaction is −284 J K−1 mol−1. Which of the following statements is not correct? A At room temperature, ΔGo = +84.4 kJ mol−1. B The reactants are less stable than the product. C The reaction is spontaneous at low temperatures and non -spontaneous at high temperatures. D There is a decrease in