Question

A quantity of an ideal gas is collected in a graduated tube over the mercury in a barometer type arrangement. the volume of gas at 20°c is 50ml and the level of mercury is 100mm above the outside of the mercury level. the atmospheric pressure is 750mm. the volume of gas at stp is​

Answer 1

Answer : The volume of gas at STP is​ 6.21 mL

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 = 100 mmHg

$P_2$ = final pressure of gas = 750 mmHg

$V_1$ = initial volume of gas = 50 mL

$V_2$ = final volume of gas = ?

$T_1$ = initial temperature of gas = $20^oC=273+20=293K$

$T_2$ = final temperature of gas at STP = $0^oC=273+0=273K$

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

$\frac{100mmHg\times 50mL}{293K}=\frac{750mmHg\times V_2}{273K}$

$V_2=6.21mL$

Therefore, the volume of gas at STP is​ 6.21 mL