ThermochemistryHard
Question
The enthalpy of combustion at 25°C of H2(g), cyclohexane(l) and cyclohexene(l) are −241, −3920 and −3800 kJ/mol, respectively. The enthalpy of hydrogenation of cyclohexene(l) is
Options
A.−121 kJ/mol
B.+121 kJ/mol
C.−242 kJ/mol
D.+242 kJ/mol
Solution
$\Delta H = \sum_{}^{}{\Delta_{C}H_{\text{Reactants}}} - \sum_{}^{}{\Delta_{C}H_{\text{Products}}} $$$= \left\lbrack ( - 3800) + ( - 241) \right\rbrack - \left\lbrack ( - 3920) \right\rbrack = - 121\text{ KJ/mol}$$
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