Question

Production of a green edged flame on igniting the vapours evolved by heating a given inorganic salt with a few ml of ethanol and conc. $H_{2}S{O}_4$ indicates the presence of :

• A. tartrate
• B. oxalate
• C. acetate
• D. borate

Answer 1

The correct option is D borate

A small quantity of the substance, a few ml of ethanol and conc. sulphuric acid is taken in a china dish. The contents are stirred with a glass rod and then ignited by the flame. The formation of the green edged flame indicates the presence of borate.

$2N{a}_{3}B{O}_3+3H_{2}S{O}_4\to 3N{a}_{2}S{O}_4+2H_{3}B{O}_3$

$H_{3}B{O}_3+3C_2{H}_{5}OH\to \underset{\text{Ethyl borate (green)}}{(C_2{H}_5{)}_{3}B{O}_3}+3H_{2}O$

So, the correct option is $B$