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JEE MainChemistryThermodynamics (C)

If the standard enthalpies of combustion of rhombic sulphur and monoclinic sulphur are -x kJ mol ⁻¹ and -y kJ mol ⁻¹ respectively, then the standard enthalpy of transition from rhombic sulphur to monoclinic sulphur is:

Options

  1. Ax - y
  2. By - x
  3. Cx + y
  4. D-(x + y)

Correct answer

B. y - x

Step-by-step solution

The combustion reactions are: (i) S(rhombic) + O ₂( g ) SO ₂( g ) H₁ = -x kJ mol ⁻¹ (ii) S(monoclinic) + O ₂( g ) SO ₂( g ) H₂ = -y kJ mol ⁻¹ The required transition reaction is: S(rhombic) S(monoclinic) This can be obtained by subtracting equation (ii) from equation (i): H_ transition = H₁ - H₂ H_ transition = -x - (-y) = y - x Answer: y - x

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