Set 11 Chemistry [Paper] 2

Page 1 | 5 SECTION A (60 Marks) Answer only three questions from this section . 1. Some of the elements in the Period 3 of the Periodic Table are sodium, aluminium, silicon, phosphorus and chlorine. a) Write the formulae of the oxide(s) of the each of the elements given above. (04 marks) b) Describe the reaction(s) of the oxides of sodi um, aluminium and phosphorus with wat er. In each case comment on the pH of the resultant solution. (05½ marks) c) Write equation : (i) For the reaction between the oxides of aluminium and silicon with aqueous sodium hydroxide. (02 marks) (ii) To show how the anhydrous chlorides of s ilicon and aluminium can be prepared. In each case state the condition(s). (04 marks) d) Aluminium chloride was dissolved in water and to the resultant solution was added concentrated potassium hydrogen carbon ate solution. State what was observe d and explain your answer. (04½ marks) 2. (a) Explain what is meant by the following terms : (i) Order of reaction (01 mark) (ii) Molecularity of a reaction (01 mark) (iii) Elementary reaction (01 mark) (b) The following data was obtained for the reaction below; Experiment [𝐴](𝑚𝑜𝑙𝐿−1) [𝐵](𝑚𝑜𝑙𝐿−1) Initial rate ( 𝑚𝑜𝑙𝐿−1𝑠−1) 1 0.03 0.03 0.3×10−4 2 0.06 0.06 1.2×10−4 3 0.06 0.09 2.7×10−4 (i) State the order of reaction with respect to 𝑨𝟐 and B. Give reasons for your answer (02marks) (ii) Write the rate equation for the reaction . (01 mark) (iii) Calculate the rate constant and its units . (02 marks) c) Draw a labeled energy diagram for the reacti on in (b) above (activation energy Ea =+250 kjmol-1, enthalpy change) (03 mark s) (ii) Calculate the activation energy for the backward reaction .(01 mark) 𝐴2(𝑔) + 2𝐵(𝑔) 2𝐴𝐵(𝑔) ∆𝐻= -50 kjmol-1 Page 2 of 5 …