Chapter 5, Problem 5.25E

At a high enough temperature, the equilibrium constant is $4.00$ for the gas-phase isotope exchange reaction

${\text{H}}_{\text{2}}+{\text{D}}_{\text{2}}\rightleftharpoons 2\text{HD}$

Calculate the equilibrium partial pressure if $0.50\text{atm}$ of ${\text{H}}_{\text{2}}$ and $0.10\text{atm}$ of ${\text{D}}_{\text{2}}$ were initially present in a $20.0\text{-L}$ system at $488\text{K}$. What is the extent of reaction at equilibrium?