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MHT CET202613 April 2026Evening ShiftChemistryThermodynamics (C)Actual

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

Options

  1. A-121 KJ mol ⁻¹
  2. B+121 KJ mol ⁻¹
  3. C-242 KJ mol ⁻¹
  4. D+242 KJ mol ⁻¹

Correct 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

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