Question

Equilibrium constants are given (in atm) for the following reactions at $0^{o}C$ $SrC{l}_2.6H_2{O}_{\left(s\right)}\rightleftharpoons SrC{l}_2.2H_2{O}_{\left(s\right)}+4H_2{O}_{\left(g\right)},$
$K_p=6.89\times {10}^{-12}$
The vapour pressure of water at $0^{o}C$ is 4.58 torr.
Calculate the pressure of water vapour in equilibrium at $0^{o}C$

• A. $2.6\times {10}^{-3}atm$
• B. $1.62\times {10}^{-3}atm$
• C. $1.20\times {10}^{-4}atm$
• D. $4.28\times {10}^{-3}atm$

Answer 1

The correct option is B $1.62\times {10}^{-3}atm$

K_p is equilibrium constant used when equilibrium concentrations are expressed in atmospheric pressure. Solid components doesnot contribute any pressure to the system. So,
$K_P=P_{H_{2}O}^4=6.89\times {10}^{-12}$
$\therefore P_{H_{2}O}=1.62\times {10}^{-3}atm$