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MHT CET202616 April 2026Evening ShiftChemistryThermodynamics (C)Actual

The heat of combustion of carbon to CO ₂ is -393.5 kJ/mol . The heat released upon formation of 35.2 g of CO ₂ from carbon and oxygen gas is

Options

  1. A+315 kJ
  2. B-315 kJ
  3. C-3.15 kJ
  4. D-630 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) The heat of combustion of carbon to CO ₂ is H = -393.5 kJ/mol . Molar mass of CO ₂ = 12 + 2 16 = 44 g/mol . Number of moles in 35.2 g of CO ₂ is: n = 35.2 44 = 0.8 mol The enthalpy change for the formation of 0.8 mol of CO ₂ is: H = 0.8 mol (-393.5 kJ/mol ) = -314.8 kJ -315 kJ The negative sign indicates that the heat is released during the process. Answer: -315 kJ

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