MHT CET Medical202625 April 2026Evening ShiftChemistryThermodynamics (C)Actual
If, i) C + 2 S CS ₂ , H = 117 kJ ii) C + O ₂ CO ₂ , H = -393 kJ iii) S + O ₂ SO ₂ , H = -297 kJ Find the heat of combustion of CS ₂ .
Options
- A-1104 kJ mol ⁻¹
- B1104 kJ mol ⁻¹
- C807 kJ mol ⁻¹
- D-807 kJ mol ⁻¹
Correct answer
A. -1104 kJ mol ⁻¹
Step-by-step solution
The required reaction for the combustion of CS ₂ is: CS ₂ + 3 O ₂ CO ₂ + 2 SO ₂ This reaction can be obtained by applying Hess's Law using the given equations. Reversing equation (i): CS ₂ C + 2 S , H₁' = -117 kJ Keeping equation (ii) as it is: C + O ₂ CO ₂ , H₂' = -393 kJ Multiplying equation (iii) by 2 : 2 S + 2 O ₂ 2 SO ₂ , H₃' = 2 (-297) = -594 kJ Adding the above three equations, we get the required reaction: CS ₂ + 3 O ₂ CO ₂ + 2 SO ₂ The heat of combustion is: H = H₁' + H₂' + H₃' H = -117 - 393 - 594 = -1104