Question
The enthalpy of combustion of cyclohexane, cyclohexene and H _2 are respectively -3920, -3800 and -241 KJ mol^ -1 . The enthalpy of hydrogenation of cyclohexene is
MHT CET
Chemistry
Thermodynamics (C)
2026
MHT CET 2026 (13 April Shift 2)
MHT CET Chemistry Question (2026) — Solution
Options
- A. -121 KJ mol^ -1
- B. +121 KJ mol^ -1
- C. -242 KJ mol^ -1
- D. +242 KJ mol^ -1
Answer
A. -121 KJ mol^ -1
Step-by-step solution
The hydrogenation reaction of cyclohexene is given by: C _6 H _ 10 + H _2 C _6 H _ 12 The enthalpy of hydrogenation can be calculated using the enthalpies of combustion of the reactants and products: H = H_c( reactants ) - H_c( products ) H = [ H_c( C _6 H _ 10 ) + H_c( H _2)] - H_c( C _6 H _ 12 ) Substituting the given values: H = [-3800 + (-241)] - (-3920) H = -4041 + 3920 H = -121 kJ mol ^ -1 Answer: -121 KJ mol^ -1
Related: Chemistry — Thermodynamics (C) · All PYQ Banks