Set 20 Chemistry [Paper] 1

1 SECTION A (46 Marks) Answer all questions from this section A 1. (a) State : (i) Raoult’s law . (01 mark ) ……………………………………………………………………………………………………… ………………………………………………… ………… …………………………………………………………………………………………… ………………………………………………… …………………… …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………………………….. (ii) Two conditions under which the law is valid . (01 mark ) ……………………………………………………………………………………………………… ………………………………………………… ………… …………………………………………………………………………………………… ………………………………………………… …………………… ……………………………………………………………………………………… …………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………. (b) Th e vapour pressure of heptane and octane are 472.2Pa and 139.8Pa respectively at a temperature of 20°C .Calculate the: (i) The vapour pressure of the mixtures containing 0.50 moles of heptane and 0.25 moles of octane at a temperature of 20°C .[Assuming the two solutions forms an ideal solution] (02 marks) ……………………………………………………………………………………………………… ………………………………………………… ………… …………………………………………………………………………………………… ………………………………………………… …………………… ………………………………………………………………………………… ………………………………………………… ……………………………… ……………………………………………………………………… ………………………………………………… ………………………………………… …………………………………………………………………………………………………………………………………………………………………….. 2 (ii) Vapour composition. (01 mark ) ……………………………………………………………………………………………………… ………………………………………………… ………… ………………………………………………………………………………………… …………………………………………………… …………………… ………………………………………………………………………………… ………………………………………………… ……………………………… ……………………………………………………………………… ………………………………………………… ………………………………………….. 2. Write equations for the reaction of the following oxides with sodium hy droxide. (1 ½ ma rks each ) (a) Aluminium (III) oxide. ……………………………………………………………………………………………………… ………………………………………………… ……………………………………………………………………………………………………… ………………………………………………… (b) Beryllium oxide ……………………………………………………………………………………………………… ………………………………………………… ………… …………………………………………………………………………………………… ………………………………………………… …………………….. (c) Lead (II) oxide ……………………………………………………………………………………………………… ………………………………………………… ………… ………………………………………………………………………………………………………………………………………… ………………………….. 3. Complete the following reaction equ ations and write the accepted mechanism. (3marks) …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… ……………………………… ……………………………………………………………………………………………… …………………………………… 3 …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… (2marks) …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………… ……………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………….. 4. (a) State what is meant by the term diagonal relationship? . (1mark) ……………………………………………………………………………………………………… ………………………………………………… ………… …………………………………………………………………………………………………………………………………………………………………… ……………………………… …………………………………………………………………………………………………… ……………………………….. (b) State three reasons why lithium and magnesium resemble. (1 ½ marks) ……………………………………………………………………………………………………… ………………………………………………… ……………………………………………………………………………………………………… ………………………………………………… ……………………………………………………………………………………………………… ………………………………………………… ………… …………………………………………………………………………………………… …………… …………………………………… …………………….. (c) Mention three properties to show the diagonal relationship between lithium and magnesium. (3marks) ……………………………………………………………………………………………………… ………………………………………………… ………… …………………………………………………………………………………………… ……………… ………………………………… …………………… ………………………………………………………………………………… ………………………………………………… ……………………………… ……………………………………………………………………… ………………………………………………… ………………………………………….. 5. 20cm3 of a gaseous hydrocarbon, X was exploded with 100cm3 of oxygen. After explosion, the volume …