Cl2=3.17g/L
Ne=.901g/L
CO2=1.96g/l
therefore Cl2 is the densest gas under the given conditions.
The correct answer is (a) wave the fumes toward your nose with your hand. If you smell the chemicals directly, it could be harmful too your health, especially if they are strong. Also remember to <em>never </em>smell chemicals unless you are being told to do so.
When a single compound breaks down into two or more compounds or elements in a chemical reaction then it is known as decomposition reaction.
The chemical symbol for sodium carbonate is
.
The decomposition of sodium carbonate is:

The decomposition of sodium bicarbonate,
will result in the formation of sodium oxide,
and carbon dioxide,
.
Hence, carbon dioxide,
will produce with sodium oxide,
on decomposition of
.