Question

The Kp for the production of phosgene is 18.0. If one mole each of CO and Cl2 are mixed at the total pressure of 1 atm, what will be the partial pressure (in atm) of COCl2 after equilibrium is reached, CO(g) + Cl2(g) <=> COCl2(g) ?

Answer 1

     Initial partial preesure of CO = ( moles of CO / total moles ) x total pressure = ( 1/1+1) x 1 atm = 0.5 atm

     Initial partial preesure of Cl2 = ( moles of Cl2 / total moles ) x total pressure = ( 1/1+1) x 1 atm = 0.5 atm             

CO(g) +    Cl2(g)    <=>    COCl2(g)

Initial                      0.5 atm        0.5 atm                  0

At equilibrium           0.5-x           0.5-x                     x

                       Kp = x / (0.5-x) (0.5-x)

                       18 = x / (0.5-x)²

                              18x² -18x +4.5 = x

                      18x² -19x +4.5 = 0

On solving,

                 x = 0.385 atm

Therefore,

partial pressure of COCl2 after equilibrium is reached = x = 0.385 atm