Example 6:

Starting with n₀ moles of water which dissociates into H₂ and O₂, show that at equilibrium

At an average temperature of 1900K, the slope of the graph   for dissociation of water vapour is found to be -13000. Find the heat of dissociation. Is it an exothermic or endothermic reaction?

Solution:

Now

Again van’t half equation

By rearrangement, we get,


Since ΔH is positive, hence the reaction is endothermic.