The combustion of one mole of benzene takes place at 298 K and 1 atm. After combustion, CO2(g) and H2O (l)
are produced and 3267.0 kJ of heat is liberated.
The standard enthalpy of formation, ∆fH⊖ of benzene is:
(Standard enthalpies of formation of CO2(g) and H2O (l) are –393.5 kJ mol–1 and – 285.83 kJ mol–1 respectively.)
1. 54. 24 kJ mol–1
2. 48. 51 kJ mol–1
3. 66. 11 kJ mol–1
4. 15. 21 kJ mol–1
Given
C(graphite)+O2( g)→CO2( g)ΔrH∘=−393.5 kJ mol−1H2(g)+12O2( g)→H2O(l)ΔrH∘=−285.8 kJ mol−1CO2( g)+2H2O(l)→CH4( g)+2O2( g)ΔrH∘=+890.3 kJ mol−1
Based on the above thermochemical equations, the value of ΔrH° at 298 K for the reaction
C(graphite)+2H2(g)→CH4(g) will be :
1. –74.8 kJ mol–1
2. –144.0 kJ mol–1
3. +74.8 kJ mol–1
4. +144.0 kJ mol–1