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COMEDK20269 May 2026Morning ShiftChemistryThermodynamics (C)Actual

The heat of combustion of carbon to CO ₂ is -393.5 kJ mol ⁻¹ . The heat released on the formation of 35.2 g of CO ₂ by combustion of C is:

Options

  1. A+620 kJ
  2. B-315 kJ
  3. C-325 kJ
  4. D+215 kJ

Correct answer

B. -315 kJ

Step-by-step solution

The combustion reaction of carbon is given by: C(s) + O ₂ (g) CO ₂ (g) H = -393.5 kJ mol ⁻¹ Molar mass of CO ₂ = 12 + 2 16 = 44 g mol ⁻¹ Number of moles of CO ₂ formed = 35.2 44 = 0.8 mol Enthalpy change for the formation of 0.8 mol of CO ₂ = 0.8 (-393.5 kJ ) = -314.8 kJ Rounding to the nearest integer, the heat released (enthalpy change) is approximately -315 kJ . Answer: -315 kJ

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