Solid carbon can react with gaseous water to form carbon monoxide gas and hydrogen gas. The equilibrium constant for the reaction at 700.0 K is Kp=1.60×10−3. If a 1.55-L reaction vessel initially contains 247 torr of water at 700.0 K in contact with excess solid carbon, find the percent by mass of hydrogen gas of the gaseous reaction mixture at equilibrium.
247 torr is divided with 760 torr/atm to obtain 0.325 atm
H2O | CO | H2 | |
Initial partial pressure (atm) | 0.325 | 0 | 0 |
Change in partial pressure (atm) | -x | x | x |
Equilibrium partial pressure (atm) | 0.325-x | x | x |
0.325 - x can be approximated to 0.325 as Kp value is small
This is a quadratic equation with roots x= 0.022, x = -0.0236
The negative value is discarded as pressure cannot be negative.
Hence, the equilibrium partial pressures are
For water,
For CO,
For H2,
The percent by mass of hydrogen gas of the gaseous reaction mixture at equilibrium %
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