Set 21 Chemistry [Paper] 2

1 SECTION A (60 Marks) Answer only three questions from this section . 1. Carbon, silicon, germanium, tin and lead are elements of group (IV) of the periodic table . a) (i).Write the outermost electronic configuration of group (IV) elements. (01 mark ) (ii).State the oxidation states of group (IV) elements. (01 mark) (iii).State how the stability of the oxidation states vary down the group (IV) elements. (02 marks) b) Describe the reactions of the elements with: i) Water. (06 marks) ii) Concentrated sulphuric acid. (06 marks) c) Write equations for the reactions between : i) Silicon (IV) oxide and hot concentrated hydrofluoric acid. (01½ marks) ii) Trileadtetraoxide and warm dilute nitric acid. (01½ marks) iii) Tin (I I) chloride solution and iron (III) sulphate solution. (01½ marks) 2. a) Phenolphthalein can be used as an acid -base indicator. i) What is meant by the term acid -base indicator ? (01 mark) ii) Describe briefly how phenolphthalein works as an acid - base indicator . (06 marks) iii) The indicator constant,K I for phenolphthalein is 5.012 x 10-10 mol/dm3.Determine the approximate pH work ing range for phenolphthalein. (02 marks) b) 25.00cm3 of 0.12M ethanoic acid was pipetted in to a conical flask and 2-3 drops of phenolphthalein indicator added and the mixture titrate d with 0.20M sodium hydroxide solution until the equivalence point had reached, when 15.00cm3 of sodium hydroxide had been used . i) What is meant by the te rm equivalence point? (01 mark ) ii) State the colour change at equivalence point . (01 mark ) iii) Calculate the pH of the mixture at equivalence point. (05 marks) c) Sketch a graph of pH against volume of sodium hydroxide for titration in (b) and explain the shape of the graph . (04 marks) 3. (a).A gaseous alkene, …