Question

Estimate ΔG°rxn for the following reaction at 417 K. HCN(g) + 2 H2(g) → CH3NH2(g) ΔH°= -158.0 kJ; ΔS°= -219.9 J/K

a. -250 kJ

b. -66.3 kJ

c. +66.3 kJ

d. +250 kJ

e. +61.9 kJ

Answer 1

The estimated standard Gibbs free energy change for the reaction at 417 K is -66.3 kJ, which is option (b).

Step-by-step explanation:

To estimate the standard Gibbs free energy change (ΔG°) for the reaction HCN(g) + 2 H₂(g) → CH₃NH₂(g) at 417 K, we use the Gibbs free energy equation:

ΔG° = ΔH° - TΔS°

Given that the standard enthalpy change (ΔH°) is -158.0 kJ and the standard entropy change (ΔS°) is -219.9 J/K, we can substitute these values into the equation. Remember, we need to convert the entropy from J/K to kJ/K by dividing by 1000:

ΔG° = (-158.0 kJ) - (417 K) * (-219.9 J/K * 1 kJ/1000 J)

ΔG° = (-158.0 kJ) - (417 K) * (-0.2199 kJ/K)

ΔG° = -158.0 kJ + 91.7 kJ

ΔG° = -66.3 kJ

Therefore, the estimated standard Gibbs free energy change for the reaction at 417 K is -66.3 kJ, which corresponds to option (b).