Question

If a gas with a volume of 12.5 L was cooled from 18 C to 0 C at constant pressure. What is the final volume

Answer 1

We can solve the problem by using Charle's law, which states that for a transformation of an ideal gas at constant pressure, the ratio between volume and absolute temperature of the gas remains constant:
$\frac{V}{T}=k$
where V is the volume of the gas and T its absolute temperature.

The previous law can be rewritten as
$\frac{V_1}{T_1}= \frac{V_2}{T_2}$ (1)
Let's convert the initial and final temperatures of the gas in Kelvin:
$T_1=18C+273=291 K$
$T_2 = 0C+273 = 273 K$
and the intiial volume is
$V_1 = 12.5 L$

so if we re-arrange equation (1) and we use these data, we can find the final volume of the gas:
$V_2=V_1 \frac{T_2}{T_1}=(12.5 L) \frac{273 K}{291 K}=11.7 L$