A gas at 772 mm Hg and at 35 °C occupies a volume of 6.851 L. Calculate its volume at STP.

Question

A gas at 772 mm Hg and at 35 °C occupies a volume of 6.851 L. Calculate its volume at STP.

Answer 1

Given: V₁ = Initial volume = 6.851 L
P₁ = Initial pressure = 772 mm Hg, P₂ = Final pressure = 760 mm Hg
T₁ = Initial temperature = 35 °C = 35 + 273.15 K = 308.15 K
T₂ = Final temperature = 273.15 K
To find: V₂ = Final volume
Formula: $\frac{{\mathrm{P}}_1{\mathrm{V}}_1}{{\mathrm{T}}_1}=\frac{{\mathrm{P}}_2{\mathrm{V}}_2}{{\mathrm{T}}_2}$
Calculation: According to combined gas law,
$\frac{P_1{V}_1}{T_1}=\frac{P_2{V}_2}{T_2}$

$V_2=\frac{P_1{V}_1{T}_2}{P_2{T}_1}=\frac{772\times 6.851\times 273.15}{308.15\times 760}=6.169L$
Ans: The volume of gas at STP is 6.169 L.