Question

A boy introduced a red hot charcoal into a gas jar and covered it with a glass lid so as to collect the gas evolved. Explain: how will he find the nature of the gas

Answer 1

The nature of the gas can tested by bringing a MOIST litmus paper to the mouth of the jar.

If the litmus paper changes its color from blue to red then the gas is  acidic

Here in this case the gas evolved is CO2 which is acidic in nature