Problem

Consider the following reaction:

\text{H}_2(\text{g}) + \text{I}_2(\text{g}) \rightleftharpoons 2\text{HI}(\text{g})

The equilibrium concentrations of hydrogen, iodine and hydrogen iodide in the reaction mixture at 760 K were found to be 0.012, 0.015 and 0.091

\text{mol dm}^{-3}

, respectively. a. Deduce the equilibrium constant expression and determine the

K

value for this reaction at 760 K. b. The

K

value for the same reaction at 715 K is 48.0. Deduce the sign of the standard enthalpy change for the forward reaction.