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The standard molar entropies of X₂, Y₂, and X₃Y₂ are 60, 40, and 50 J K⁻¹ mol⁻¹, respectively. For the reaction 1/2 X₂ + 3/2 Y₂ → X₃Y₂, if ΔH = −30 kJ, the temperature at which the system is in equilibrium is

1. 1250 K
2. 500 K
3. 750 K
4. 1000 K

Correct answer: 750 K

Solution

The equilibrium temperature can be determined using the Gibbs free energy equation, which relates enthalpy, entropy, and temperature. In this case, the negative enthalpy change and the calculated change in entropy for the reaction indicate that the reaction is spontaneous at 750 K, making it the correct answer.

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