GIBB’S FREE ENERGY PROBLEMS WORKSHEET
Answer: feel free to question my math. Also, sig figs.
1. The hydrogenation of ethene gas under standard conditions (T = 298.15 K) shows a decrease in
disorder (ΔS˚ = -0.1207 kJ/(mol•K)) during an exothermic reaction (ΔH˚ = -136.9 kJ/mol).
Determine whether the reaction is spontaneous or nonspontaneous by calculating ΔG˚.
C2H4 (g) + H2 (g) → C2H6 (g)
Go=-100.9 KJ/mol yes, spontaneous
2. Calculate the standard free energy of the following reaction from standard free energies of
formation.
2 CO (g) + O2 (g) → 2 CO2 (g)
Go = -1063 KJ/mol
3. The vaporization of bromine requires 31.0 kJ/mol and an increase in disorder (ΔS˚ = 93.0
J/(mol•K)). At what temperature will this process be spontaneous?
Br2 (l) → Br2 (g)
T> 333 K
4. Calculate the standard free energy for the following reaction producing glucose.
6 CO2 (g) + 6 H2O (l) → C6H12O6 (s) + 6 O2 (g)
Go = 2879 KJ/mol
5. Copper (I) sulfide reacts with sulfur to produce copper (II) sulfide under standard conditions. The
process is exothermic (ΔH˚ = -26.7 kJ/mol) with a decrease in disorder (ΔS˚ = -19.7 J/(mol•K)).
Determine the spontaneity of the reaction by calculating ΔG˚.
Cu2S (s) + 2 S (s) → 2 CuS (s)
Go = -20.8 KJ/mol yes, spontaneous
