Question

A gas reacts with $CaO$, but not with $NaHC{{O}_{3}}$. The gas is
A. Carbon dioxide
B. Chlorine
C. Nitrogen
D. Oxygen

Answer 1

Hint: Calcium oxide is a basic oxide. Sodium bicarbonate is a weak base. Due to weak basic properties it does not react with chlorine gas.

Complete Step by Step Answer:
Chlorine is a halogen element.
Chlorine gas reacts with basic calcium dioxide to form calcium hypochlorite which is also known as bleaching powder.
The reaction is given as: $C{{l}_{2}}+CaO\to Ca(OCl)Cl$

Chlorine gas is an acidic gas and calcium hydroxide is a strong base so, both react to form calcium hypochlorite or bleaching powder. Sodium bicarbonate is a weak base so it does not react with acidic chlorine gas. Thus no reaction takes place.

The chemical formula of bleaching powder is $Ca(OCl)Cl$. Thus bleaching powder contains chlorine. So, chlorine is widely used as a bleaching agent. Chlorine can bleach colored substances and make the substances colourless. Thus we can write that the gas is chlorine gas.
Thus the correct option is B.

Note: The reaction of chlorine gas with any bases is a neutralisation type of reaction. Like all neutralisation reactions, salt and water is also formed here.