Question

A sample of Freon-12 (CF2Cl2) occupies 2.842 x 101 L at 331 K and 2.525 x 102 kPa. Find its volume (in L) at standard temperature and pressure (STP).

Answer 1

We have to first find the number of moles of Freon-12 in the sample using the ideal gas law equation
PV = nRT
n = $\frac{PV}{RT}$
since the number of moles at both conditions given and at stp we can write the following formula 
$\frac{P1V1}{RT1} = \frac{P2V2}{RT2}$
where parameters for the given conditions are on the left side and parameters for STP conditions are on the right side of the equation
where P1 - pressure - 252.5 kPa
V1 - volume - 28.42 x 10⁻³ m³ 
R - universal gas constant 
T1 - 331 K

STP conditions 
P2 - 101 325 Pa
T2 - 273 K

substituting these values in the equation 

$\frac{252 500Pa*28.42*10 ^{-3}m^{3} }{R*331K} = \frac{101325 Pa*V}{R*273 K}$

V = 58.41 L
Volume at STP is 58.41 L