Set 8 Chemistry [Paper] 1

1 SECTION A (46 Marks) Answer all questions from this section A 1. (a) Write: (i) equation for ionization of methanoic acid in water. (1 ½ marks) ……………………………………………………………………………………………………… ………………………………………………… ………… …………………………………………………………………………………………… ………………………………………………… …………………….. (ii) the expression for the acid constant Ka, for methanoic acid. (½ mark ) ……………………………………………………………………………………………………… ………………………………………………… ………… …………………………………………………………………………………………… ………………………………………………… …………………….. (b) Th e molar conductivity of 0.1M methanoic acid solution at 25oC is 16.2 scm2 mol-1. Calculate the: (i) Degree of ionisation of methanoic acid at 25oC (molar conductivity of methanoic acid at infinite dilution at 25oC is 40 scm2 mol-1) (1 ½ marks) ……………………………………………………………………………………………………… ………………………………………………… ………… …………………………………………………………………………………………… ………………………………………………… …………………… ………………………………………………………………………………… ………………………………………………… ……………………………… ……………………………………………………………………… ………………… ……………………………… ………………………………………… …………………………………………………………………………………………………………………………………………………………………….. (ii) Ionization constant, Ka for methanoic acid at 25oC. (1 ½ marks) ……………………………………………………………………………………………………… ………………………………………………… ………… ……………………………………………………………………… …………………… ………………………………………………… …………………… ………………………………………………………………………………… ………………………………………………… ……………………………… ……………………………………………………………………… ………………………………………………… ………………………………………….. 2. Write equations for the reaction of the following oxides with sodium hy droxide. (1 ½ marks each ) (a) Chromium (III) oxide. ……………………………………………………………………………………………………… ………………………………………………… ……………………………………………………………………………………………………… ………………………………………………… 2 (b) Beryllium oxide ……………………………………………………………………………………………………… ………………………………………………… ………… …………………………………………………………………………………………… ………………………………………………… …………………….. (c) Lead (II) oxide ……………………………………………………………………………………………………… ………………………………………………… ………… ………………………………………………………………………………………………………………………………………… ………………………….. 3. Complete the following reaction equ ations and write the accepted mechanism. (3marks) …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… ……………………………… ……………………………………………………………………………………………… …………………………………… …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… (2marks) …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………… ……………………………………………………………………………… …………………………………………………………………………………………………………………………………………………………………….. 4. (a) State what is meant by the term diagonal relationship? . (1mark) ……………………………………………………………………………………………………… ………………………………………………… ………… …………………………………………………………………………………………………………………………………………………………………… ……………………………… …………………………………………………………………………………………………… ……………………………….. (b) State three reasons why lithium and magnesium resem ble. (1 ½ marks) ……………………………………………………………………………………………………… ………………………………………………… ……………………………………………………………………………………………………… ………………………………………………… 3 ……………………………………………………………………………………………………… ………………………………………………… ………… …………………………………………………………………………………………… …………………………… …………………… …………………….. (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 a nd cooling …