Question

Which is the odd one out out of these individual questions?

Nitrous oxide
Carbon dioxide
Air

Oxygen
Carbon monoxide
Helium

Nitrous oxide
Carbon dioxide
Air

Salt (Sodium chloride)
Sodium metal
Sodium bicarbonate (baking soda)

Answer 1

1. Air

Others are chemical compounds, air is a mixture.

2. Carbon monoxide

Others are elements, carbon monoxide is compound.

3. Air

Others are compounds, air is not.

4. Sodium metal

Sodium metal is element, others are compounds.