103mL of carbon dioxide was collected at  ${27}^{0}C$ and 763 mm pressure. What will be its volume if the pressure is changed to 721mm at the same temperature ?

Given conditions 
$\begin{array}{l}{V}_1=103mL\\ P_1=750mm\end{array}$
Final condition
$\begin{array}{l}{V}_2=?mL\\ P_2=721mm\end{array}$
By applying Bole’s law since temperature is constant,
$P_2\times V_2=P_1\times V_1$
Substituting the corresponding values, we have 
$\begin{array}{l}721\times V_2=763\times 103\\ V_2=\frac{763\times 103}{721}=190mL\end{array}$
Therefore, the volume of carbon dioxide is 109mL.