The enthalpy of combustion of\[{{H}_{2}},\]cyclohexene\[({{C}_{6}}{{H}_{10}})\]and cyclohexane\[({{C}_{6}}{{H}_{12}})\]are\[-241,~-3800\] and\[-3920\text{ }kJ\]per mol respectively. Heat of hydrogenation of cyclohexene is
A) \[-121\text{ }kJ\] per mol
B) \[+121\text{ }kJ\] per mol
C) \[+242\text{ }kJ\] per mol
D) \[-242\text{ }kJ\] per mol
Correct Answer:
A
Solution :
\[\Delta H=?\] \[\Delta H=[\Delta H\]of combustion of cyclohexan\[-(\Delta H\] of combustion of cyclohexene\[+\Delta H\]of combustion of\[{{H}_{2}}\])] \[=-[-3920-(3800-24)]\text{ }kJ\] \[=-[3920+4041]\] \[=-[121]kJ\] \[=-121kJ\]