Question

(a) With respect to the Brown Ring Test, explain the following:
(i) The brown ring disappears if the test tube is disturbed.
(ii) Lead nitrate does not respond well to this test.

(b) Write a balanced chemical equation for the reaction of sodium carbonate with dilute nitric acid. [5 MARKS]

Answer 1

a) 4 Marks
b) 1 Mark

(a) (i) The brown ring disappears if the test tube is disturbed because the unstable nitrosoferrous sulphate decomposes on shaking. This is due to the heat liberated when concentrated sulphuric acid and water are mixed together.

(ii) Lead nitrate formed from lead oxide forms insoluble sulphate. i.e. lead sulphate which does not respond well to the brown ring as insoluble residue interferes with the result of the test.

(b) $N{a}_{2}C{O}_3+2HN{O}_3(dil.)\to 2NaN{O}_3+H_{2}O+C{O}_2\uparrow$