Solid carbon can react with gaseous water to form carbon monoxide gas and hydrogen gas. The equilibrium constant for the reaction at 700.0 {\rm K} is K_{{\rm p}}=1.60 \times 10^{-3}.
If a 1.55-{\rm L} reaction vessel initially contains 153 torr of water at 700.0 {\rm K} in contact with excess solid carbon, find the percent by mass of hydrogen gas of the gaseous reaction mixture at equilibrium.