The synthesis of HBr from hydrogen and liquid bromine has an equilibrium constant Kp `= 4.5×x10^(15)` at 25°C. Given that the vapor pressure of liquid bromine is 0.28 atm, find Kp for the homogeneous gas-phase reaction at the same temperature.

Explanation

The net reaction we seek is the sum of the heterogeneous synthesis and the reverse of the vaporization of liquid bromine:
`H_(2)(g)+Br_(2)(l)to2HBr(g)K_(p)=4.5xx10^(15)`
`Br_(2)(g)toBr_(2)(l)K_(p)=(0.28)^(-1)`
`bar(H_(2)(g)+Br_(2)(g)to2HBr(g)K_(p)=1.6xx10^(19))`
Here are some of the possibilities for the reaction involving the equilibrium between gaseous water and its elements: