Question

Which of the following salt has an outcome of blue colour as a result of a borax bead test?

(a) Nickel sulphate

(b) Cobalt sulphate

(c) Ferrous sulphate

(d) Chromium sulphate

This question was posed to me in an internship interview.

I'd like to ask this question from p-Block Elements in section p-Block Elements of Chemistry – Class 11

Answer 1

Correct option is (b) Cobalt sulphate

The best explanation: Cobalt sulphate on heating gives cobalt oxide and sulphur trioxide, further cobalt oxide is combined with boric anhydride which gives cobalt metaborate which is a blue coloured Bead, the colours of iron, chromium and Nickel are green, green and brown respectively.