Answer : The new or final volume of gas will be, 11.4 L
Explanation :
Charles' Law : It is defined as the volume of gas is directly proportional to the temperature of the gas at constant pressure and number of moles.
[tex]V\propto T[/tex]
or,
[tex]\frac{V_1}{V_2}=\frac{T_1}{T_2}[/tex]
where,
[tex]V_1[/tex] = initial volume of gas = 12.1 L
[tex]V_2[/tex] = final volume of gas = ?
[tex]T_1[/tex] = initial temperature of gas = [tex]9^oC=273+9=282K[/tex]
[tex]T_2[/tex] = final temperature of gas = [tex]-7^oC=273+(-7)=266K[/tex]
Now put all the given values in the above formula, we get the final volume of the gas.
[tex]\frac{12.1L}{V_2}=\frac{282K}{266K}[/tex]
[tex]V_2=11.4L[/tex]
Therefore, the new or final volume of gas will be, 11.4 L