A gas occupies a volume of  ${\text{250 cm}}^{\text{3}}$  at 745 torr and$25°\text{C}$ . What additional pressure is required to reduce the gas volume to ${\text{200 cm}}^{\text{3}}$  at the same temperature

${\text{P}}_{\text{1}}{\text{V}}_{\text{1}}={\text{P}}_{\text{2}}{\text{V}}_{\text{2}}$

$\Rightarrow 745\times 250={\text{P}}_{\text{2}}\times 200$

$\Rightarrow {\text{P}}_{\text{2}}=\frac{745\times 250}{200}=931.5\text{ torr}$

${\text{Additional pressure = P}}_{\text{final}}-{\text{P}}_{\text{initial}}$

$\text{Additional pressure = 931}\text{.5 }-\text{745}$

                                 $\text{=186}\text{.5 torr}$