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 the degree of disorderliness.

4 [Turn Over 9. The following experimental results are obtained for a reaction with the general rate equation of: rate = k [M]x [N]y [L] Experiment [M] / mol dm-3 [N] / mol dm-3 [L] / mol dm-3 Relative rate 1 0.1 0.2 0.3 1 2 0.2 0.6 1.2 72 Which of the following are possible values of x and y? x y A 1 1 B 2 1 C 1 2 D 2 2 10. Which of the following will decrease the rate constant for a reaction? A Decrease in concentration B Decrease in temperature C Decrease in pressure D Addition of catalyst

5 [Turn Over 11. Phosphorus trichloride and chlorine react according to the following equation: PCl3(g) + Cl2(g) PCl5(g) A mixture of PCl3 and Cl2 was placed in a syringe and brought to equilibrium at time t and the following graph was obtained. Which of the following accounts for the drop in [PCl3] at time t? A PCl5 was added to the mixture B Argon gas was added to the mixture C The syringe was heated D The plunger of the syringe was withdrawn until the volume was twice the initial volume 12. Which of the following statements about phosphoric(V) acid is not correct? A HPO4 2- has a higher Kb value than H2PO4 -. B PO4 3- can react as a base. C H2PO4 - can react both as an acid and as a base. D H3PO4 has a higher pKa than HPO4 2-. 13. 95 cm3 of M2+ ions is mixed with an an equal volume of X - ions at 25 oC. Which of the following initial concentrations of M2+ and X- will result in the precipitation of MX2? (Ksp of MX2 = 7.67 x 10-13 mol3 dm-9) [M2+] / 10-4 mol dm-3 [X-] / 10-4 mol dm-3 A 1 1 B 1 2 C 2 1 D 2 2

6 [Turn Over 14. Use of the Data Booklet is relevant to this question. Glucose can be reacted with silver ions to form a silver mirror in the following reaction. C6H12O6 + 2Ag+ + H2O  2Ag + C6H12O7 + 2H+ E cell = +0.75 V Which of the following metal ions cannot be used for a possible reaction with glucose? A Mn3+ B V3+ C Fe3+ D Co3+ 15. Use of the Data Booklet is relevant to this question. The following reaction does not occur under standard conditions. 2NO3 ─ (aq) + 8H+ (aq) + 6Cl─ (aq) 2NO (g) + 4H2O (l) + 3Cl2 (g) Which of the following can result in the reaction occuring? A Decreasing the volume of the reaction vessel B Addition of nitrogen monoxide C Decreasing the pH D Addition of chlorine 16. The properties of the oxides of four Period 3 elements W, X, Y and Z are given below.  The oxide of W is insoluble in water and in dilute acid but soluble in concentrated sodium hydroxide.  The oxide of X is amphoteric.  The oxide of Y reacts with dilute potassium hydroxide at room temperature.  The oxide of Z dissolves in water to form a solution of pH = 13. Which of the following is correct in order of increasing atomic number? A Z, X, W, Y C Z, W, X, Y B W, X, Y, Z D Z, Y, W, X

7 [Turn Over 17. The following graphs show how two properties of the elements, Na to P, and their compounds, vary with proton number. proton number proton number Graph 1 Graph 2 What properties are shown by the two graphs? Graph 1 Graph 2 A Melting point of oxide Conductivity of element B Melting point of oxide Melting point of chloride C Melting point of chloride Melting point of oxide D Melting point of element Conductivity of element 11 12 13 14 15 11 12 13 14 15

8 [Turn Over 18. A student observed the reactions when sodium chloride was added separately to concentrated sulfuric acid and concentrated phosphoric acid. The experiment was repeated using sodium iodide. Reagent Observation with sodium chloride Observation with sodium iodide conc. H2SO4 white fumes evolved purple vapour evolved conc. H3PO4 white fumes evolved white fumes evolved Which deduction can be made from these observations? A The reducing power of HI is greater than that of HCl. B The bond length of HI is smaller than that of HCl. C Concentrated phosphoric acid is a stronger oxidising agent than concentrated sulfuric acid. D Basicity of concentrated phosphoric acid is greater than concentrated sulfuric acid. 19. The following data refer to cobalt as a typical transition element and calcium as an s-block element. Which of the following properties shows the correct data for both elements? Property Cobalt C