Question

Chlorine, nitrogen, ammonia and sulphur dioxide gases are collected under the same conditions of temperature and pressure.
Copy the following table which gives the volumes of the gases collected, and the number of molecules (X) in 20 litres of nitrogen. You are to complete the table by giving the number of molecules in the other gases, in terms of X.

Gas	Volume (litres)	Number of molecules
Chlorine Nitrogen Ammonia Sulphur dioxide	10 20 20 5	X

Answer 1

Using ideal gas equation, we determine the number of molecules of nitrogen present in 20 L of the gas.
Number of molecules of nitrogen = $\frac{P\times V}{\mathrm{R}T}\times \mathrm{Avogadro}\text{'}\mathrm{s}\mathrm{constant}$
At same temperature and pressure of all gases,
$\frac{P\times \mathrm{Avogadro}\text{'}\mathrm{s}\mathrm{constant}}{\mathrm{R}\times T}=\mathrm{constant}$
Number of molecules in 20 litres of nitrogen = Volume of nitrogen = X
Similarly, number of molecules of all the gases can be determined.

Gas	Volume (litres)	Number of molecules
Chlorine	10	$\frac{X}{2}$
Nitrogen	20	X
Ammonia	20	X
Sulphur dioxide	5	$\frac{X}{4}$