Question

At constant pressure, a gas occupies a volume of 6L at $120°\mathrm{C}$. What will be the volume of a gas when the temperature decreases by $40°\mathrm{C}$.

Answer 1

It is given in a question that

Pressure = constant

$$\begin{gathered} {\mathrm{V}}_1=6\mathrm{L} \\ {\mathrm{T}}_1=120°\mathrm{C}(273+120)=393 \\ {\mathrm{V}}_2=? \\ {\mathrm{T}}_2=40°\mathrm{C}(273+40)=313 \end{gathered}$$

As the pressure is constant Charle's law is applicable here-

According to Charle's law-

$\frac{{\mathrm{V}}_1}{{\mathrm{T}}_1}=\frac{V_2}{T_2}$

$$\begin{gathered} \frac{6}{393}=\frac{V_2}{313} \\ {\mathrm{V}}_2=\frac{6\times 313}{393} \\ {\mathrm{V}}_2=4.77\mathrm{L} \end{gathered}$$

So, the final volume will be 4.77L.