Question

A gas inside a piston initially has a pressure of 1.2 bars at temperature of 25 degree C and volume of 20.0 mL. If temperature is increased to 120 deg C and the piston expands to a volume of 80 mL, what is the new pressure

Answer 1

Answer: The new pressure is 0.39 bar

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 = 1.2 bar

$P_2$ = final pressure of gas = ?

$V_1$ = initial volume of gas = 20.0 ml

$V_2$ = final volume of gas = 80.0 ml

$T_1$ = initial temperature of gas = $25^oC=273+25=298K$

$T_2$ = final temperature of gas = $120^oC=273+120=393K$

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

$\frac{1.2\times 20.0}{298}=\frac{P_2\times 80.0}{393}$

$P_2=0.39bar$

The new pressure is 0.39 bar