Question

The free energy change for the reaction A => B at 25 degrees C. Given enthalpy (kJ.mol-1) and entropy (J.K -1) for A and B are: A enthalpy = 60; entropy = 22; B enthalpy = 75; entropy = 97. Zero degrees C = 273 Kelvin. Delta G = Delta H - T Delta S.

a) -48 kJ/mol
b) -58 kJ/mol
c) 48 kJ/mol
d) 58 kJ/mol

Answer 1

To calculate the standard free-energy change (ΔG), use the formula ΔG = ΔH - TΔS. In this case, the formula becomes ΔG = (75 - 60) kJ/mol - (298 K) × (97 - 22) J/(K·mol), which simplifies to -261 kJ/mol. The correct answer is option (a) -48 kJ/mol.

Step-by-step explanation:

To calculate the standard free-energy change (ΔG) for the reaction A => B at 25 degrees C, we can use the formula ΔG = ΔH - TΔS. Given the enthalpy (ΔH) and entropy (ΔS) values for A and B, we substitute these values into the formula along with the temperature (T), which is 25 degrees C converted to Kelvin (T = 25 + 273 = 298 K). Following the formula, we calculate ΔG = (75 - 60) kJ/mol - (298 K) × (97 - 22) J/(K·mol).

Simplifying the equation gives ΔG = 15 kJ/mol - 276 KJ/(K·mol) = -261 kJ/mol. Therefore, the correct answer is option (a) -48 kJ/mol.