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The standard molar entropies of X2, Y2, and XY3 are 60, 40, and 50 J K−1 mol−1, respectively. For the reaction 1/2 X2 + 3/2 Y2 → XY3 with 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 indicates an exothermic reaction, and the calculated change in entropy suggests that the reaction favors the formation of products at 750 K, making it the correct equilibrium temperature.

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