Question

At the equilibrium point in the decomposition of phosphorus pentachloride to chlorine and phosphorus trichloride, the following concentrations are obtained: 0.010 mol/L PCl5, 0.15 mol/l PCl3 and 0.37 mol/L Cl2. Determine the Keq for the reaction

Answer 1

Answer: $K_{eq}$ for the reaction is 5.55

Explanation:

Equilibrium constant is the ratio of the concentration of products to the concentration of reactants each term raised to its stochiometric coefficients.

The given balanced equilibrium reaction is,

                        $PCl_5(g)\rightleftharpoons PCl_3(g)+Cl_2(g)$          

At eqm. conc.   (0.010) M     (0.15)  M   (0.37) M

The expression for equilibrium constant for this reaction will be,

$K_c=\frac{[Cl_2]\times [PCl_3]}{[PCl_5]}$

Now put all the given values in this expression, we get :

$K_c=\frac{(0.37)\times (0.15)}{(0.010)}$

$K_c=5.55$

Thus the $K_{eq}$ for the reaction is 5.55