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MHT CET202620 April 2026Evening ShiftChemistryThermodynamics (C)Actual

The enthalpy of combustion of C, H ₂ , and CH ₄ are -390 , -285 and -890 kJ/mol. Find the enthalpy of formation of methane.

Options

  1. A-70 kJ
  2. B-111 kJ
  3. C-170 kJ
  4. D-85 kJ

Correct answer

A. -70 kJ

Step-by-step solution

The required reaction for the formation of methane is: C(s) + 2 H ₂ (g) CH ₄ (g) The enthalpy of formation can be calculated using the enthalpies of combustion of the reactants and products: H_f( CH ₄) = H_c( C ) + 2 H_c( H ₂) - H_c( CH ₄) Substituting the given values: H_f( CH ₄) = -390 + 2(-285) - (-890) H_f( CH ₄) = -390 - 570 + 890 H_f( CH ₄) = -960 + 890 = -70 kJ/mol Answer: -70 kJ

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