question_answer

Out of the following reactions, in which case heat evolved will be more? \[{{H}_{2}}(g)+\frac{1}{2}\,{{O}_{2}}(g)\xrightarrow{\,}\,{{H}_{2}}O(g)\] \[{{H}_{2}}(g)+\frac{1}{2}\,{{O}_{2}}(g)\xrightarrow{\,}\,{{H}_{2}}O(l)\]

Answer:

                Both the reactions are exothermic in nature but the heat evolved in the second case will be more because, when \[{{H}_{2}}O(g)\] changes to \[{{H}_{2}}O(l),\] energy is released in the process of liquefication.