Question

2Ca(s) + O₂(g) → 2CaO(s)

ΔH°rxn= -1269.8 kJ
ΔS°rxn= -364.6 J/K

a. Calculate the free energy change for the reaction at 35°C.
i. -1043.3 kJ
ii. -1343.3 kJ
iii. -964.5 kJ
iv. -1143.5 kJ

b. Is the reaction spontaneous?
i. Yes
ii. No

Answer 1

To calculate the free energy change at 35°C, use the Gibbs free energy equation ΔG = ΔH - TΔS. Upon calculating, ΔG is -1157.42 kJ, and since this is negative, the reaction is spontaneous. However, this calculated value does not match any of the provided options, suggesting an error in options or calculation.

Step-by-step explanation:

To calculate the free energy change (ΔG) for the reaction at 35°C, use the Gibbs free energy equation: ΔG = ΔH - TΔS. First convert 35°C to Kelvin by adding 273.15 (35 + 273.15 = 308.15 K). Then convert ΔS from J/K to kJ/K by dividing by 1000 (ΔS = -364.6 J/K ÷ 1000 = -0.3646 kJ/K). Plug in the values:

ΔG = (-1269.8 kJ) - (308.15 K × -0.3646 kJ/K)

ΔG = -1269.8 kJ + 112.38 kJ

ΔG = -1157.42 kJ

However, this value is not one of the options provided, indicating there might be a potential mistake in calculations or in the options provided. If the calculations are correct, and the options are indeed incorrect, it could be that the closest correct option (based on the result of calculations) is i. -1143.5 kJ, but this would still be problematic.

The reaction is spontaneous if ΔG is negative. Based on our calculation, ΔG is negative; thus, the reaction is spontaneous under the given conditions.