Question

If 100 cm³ of oxygen contain Y molecules, how many molecules of nitrogen will be present in 50 cm³ of nitrogen under same conditions of temperature and pressure.

Answer 1

According to Avogadro's law, under the same conditions of temperature and pressure, equal volumes of all gases contain the same number of molecules.

Example to illustrate Avogadro's law :

If 100 ml of H₂ at S.T.P contains n molecules of H₂ then :

(a) 100 ml of N₂ at S.T.P contains n molecules;

(b) 100 ml of O2 at S.T.P contains n molecules.

According to the given question,

If 100 cm³ of oxygen = Y molecules of oxygen then

100 cm³ of nitrogen = Y molecules of nitrogen under the same conditions of temperature and pressure.

So, 50 cm³ ( $\frac{100}{2}$) of nitrogen will contain = $\frac{Y}{2}$molecules of nitrogen.