Question

1.22gm of a gas measured over water at 15 degree Celsius and pressure of 775mm of Hg occupied 900ml. Calculate the volume of dry gas at NTP. vapour pressure of water at 15 degree Celsius is 14mm (T=298K)

Answer 1

Answer : The volume of dry gas at NTP is 51.55 L

Explanation :

Combined gas law is the combination of Boyle's law, Charles's law and Gay-Lussac's law.

The combined gas equation is,

$\frac{P_1V_1}{T_1}=\frac{P_2V_2}{T_2}$

where,

$P_1$ = initial pressure of gas = 775 mmHg

$P_2$ = final pressure of gas = 14 mmHg

$V_1$ = initial volume of gas = 900 mL

$V_2$ = final volume of gas = ?

$T_1$ = initial temperature of gas = $15^oC=273+15=288K$

$T_2$ = final temperature of gas at NTP = $25^oC=273+25=298K$

Now put all the given values in the above equation, we get:

$\frac{775mmHg\times 900mL}{288K}=\frac{14mmHg\times V_2}{298K}$

$V_2=51551.34mL\approx 51.55L$

Therefore, the volume of dry gas at NTP is 51.55 L