At 25°C and 760 mm of Hg pressure a gas occupies 600 mL volume. What will be its pressure at a height where temperature is 10°C and volume of the gas is 640 mL?

${\mathrm{p}}_1=760 \mathrm{mmHg},{\mathrm{V}}_1=600 \mathrm{mL},{\mathrm{T}}_1=25+273=298 \mathrm{K}$

${\text{V}}_2=640 \mathrm{mL} \mathrm{and} {\mathrm{T}}_2=10+273=283 \mathrm{K}$

According to combined gas law,

$\frac{{\mathrm{p}}_1{\mathrm{V}}_1}{{\mathrm{T}}_1}=\frac{{\mathrm{p}}_2{\mathrm{V}}_2}{{\mathrm{T}}_2}$

$\Rightarrow$   ${\mathrm{p}}_2=\frac{{\mathrm{p}}_1{\mathrm{V}}_1{\mathrm{T}}_2}{{\mathrm{T}}_1{\mathrm{V}}_2}$

$\Rightarrow$  ${\mathrm{p}}_2=\frac{(760 \mathrm{mmHg})\times (600 \mathrm{mL})\times (283 \mathrm{K})}{(640 \mathrm{mL})\times (298 \mathrm{K})}$

= 676.6 mmHg $\approx$ 677 mmHg