question_answer

Consider the following reactions:

(a) \[{{H}^{+}}_{(aq)}+O{{H}^{-}}_{(aq)}={{H}_{2}}{{O}_{(l)}},\,\,\,\Delta H=-{{X}_{1}}kJ\,mo{{l}^{-1}}\]

(b) \[{{H}_{2(g)}}+\frac{1}{2}{{O}_{2(g)}}={{H}_{2}}{{O}_{(l)}},\,\,\,\Delta H=-{{X}_{2}}\,kJ\,mo{{l}^{-1}}\]

(c) \[C{{O}_{2(g)}}+{{H}_{2(g)}}=C{{O}_{(g)}}+{{H}_{2}}{{O}_{(l)}}-{{X}_{3}}kJ\,mo{{l}^{-1}}\]

(d) \[{{C}_{2}}{{H}_{2(g)}}+\frac{5}{2}{{O}_{2(g)}}=2C{{O}_{2(g)}}+{{H}_{2}}{{O}_{(l)}}+{{X}_{4}}kJmo{{l}^{-1}}\]

Enthalpy of formation of \[{{H}_{2}}{{O}_{(l)}}\] is:

A)  \[+{{X}_{1}}\,kJ\,mo{{l}^{-1}}\]            

B)  \[-{{X}_{2}}\,kJ\,mo{{l}^{-1}}\]

C)  \[+{{X}_{3}}\,kJ\,mo{{l}^{-1}}\]            

D)  \[-{{X}_{4}}\,kJ\,mo{{l}^{-1}}\]