Question

Given the following equilibrium:

Br2 (g) + F2 (g) <----> 2 BrF (g)

Kc = 54.7 at 300 K

An evacuated flask is charged with 2.2 atm of Br2 and 2.2 atm of F2 at 300 K. Calculate the partial pressure of BrF at equilibrium at this temperature.

Answer 1

                               Br₂ (g) + F₂ (g)      2 BrF (g)

initial pressure        2.2         2.2                  0

change                     -p           -p                 +2p

Equb pressure       2.2-p      2.2-p                 2p

Equilibrium constant , K_c = p²_BrF(g) / ( p_Br2(g) x p _F2(g) )

                              54.7 = (2p)² / [(2.2-p)(2.2-p)]

                    2p / (2.2-p) = 7.39

            2p = 16.3 - 7.39p

                          9.39 p = 16.3

                                 p = 1.73 atm

Therefore the equilibrium partial pressure of BrF = 2p = 2x1.73 = 3.46 atm