Set 5 Chemistry [Paper] 1

‘When schools flourish, all flourishes’ Tr.Felix Js Rubangakene Geofrey Jr 1 SECTION A -46 MARKS Attempt all questions in this section. 1. Uranium undergoes nuclear decay according to the following equation . 𝑼 𝟗𝟐𝟐𝟑𝟖+ 𝛂 X + 𝛃 Y + 𝛃 Z a) Identify the species X, Y & Z . (03 marks) X: ………………………………………………………………………………………………………………… Y: ………………………………………………………………………………………………………………… Z: ………………………………………………………………………………………………………………… b) 10.0g of Uranium was left to decay to deca y. Calculate the mass of Uranium that remained after 2.5 x 109years. [Half-life of Uranium, t ½ = 4.5 x 109years] (03 marks) ……………………………………………………………………………………………………………………… ………………………………………………………………………………………………………… ………….. …………………………………………………………………………………… ………………………………… …………………………………………………………………………………………………………………….. ……………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………… ………………………………………… …………………………………………………………………………… …………………………………………………………………………………………………………………… 2. Write for the reaction between aqueous sodium hydroxide solution and: a) Beryllium oxide. (01½ marks) ……………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………… ‘When schools flourish, all flourishes’ Tr.Felix Js Rubangakene Geofrey Jr 2 b) Chromium (III) oxide . (01½ marks) ……………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………… c) Sulphur (IV) oxide. (01½ marks) ………………… ………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………… 3. Complete the equations and write the accepted mechanism in each case. CH3CH2CHCH3Conc.H2SO4(l) Heat OHa) ......................... (02½ marks) ………………………………………………………………………………………………… …………………… ……………………………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………… ……………………………………………………………………………………………… …………………….. ……………………………………………………………………………………………………………………… ………………………………………………………………………………………………………… …………. b)Conc.H2SO4(l) Heat....................................... (02½ marks) ……………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………… ……………………………………………………………………………………………… ……………………… …………………………………… ………………………………………………………………………………… …………………………………………………………………………………… ………………………………. ‘When schools flourish, all flourishes’ Tr.Felix Js Rubangakene Geofrey Jr 3 4.(a) State: (@01 mark ) i. Raoult’s law. ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………… ……………………………………………………………………………………… ………………………………………………………………………………………………………………… ii. Two conditions under which the law is valid. ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… b) The vapour pressures of heptane and octane are 473.2 and 139.8Pa at a temperature of 20 ᵒC. Calculate: i. The vapour pressure of a mixture containing 0.5moles of heptane and 0.25moles of octane at the same temperature. [ Assume that the two liquids forms ideal solution] (02 marks) ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………… ……………………………………… ……………………………………………………………………….. ii. The composition of the vapour . (02 marks) …………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………… ……………………………………………………………………………… …………………………………………. ‘When schools flourish, …