The +1 oxidation state is the most stable state for Tl, but it is not as common for Ga. Calculate the standard potential and standard Gibbs free energy (in kJ) for the disproportionation reaction below to explain this phenomenon


3 M⁺(aq) → M³⁺ (aq) + 2 M (s)              M = Ga or Tl


Is the reaction spontaneous for either Ga⁺ or Tl⁺? The relevant standard reduction potentials are listed below
Tl³⁺(aq) + 2 e^-→ Tl⁺ (aq)                  E° = +1.25 V
Tl⁺(aq) + e^-→ Tl (s)                          E° = -0.34 V
Ga³⁺(aq) + 2 e^-→ Ga⁺ (aq)               E° = -0.35 V
Ga⁺(aq) + e^-→ Ga (s)                       E° = -0.20 V

• A. Tl⁺: E° = -1.59 V, ΔG° = +250 kJ, non-spontaneousGa⁺: E° = -0.15 V, ΔG° = -28.9 kJ, spontaneousThe +1 oxidation state is the most stable state for Tl, but it is not as common for Ga, because the disproportionation reaction for the formation of Tl⁺³ is non-spontaneous, while it is spontaneous for Ga³⁺_.
• B. Tl⁺: E° = -1.59 V, ΔG° = +307 kJ, non-spontaneousGa⁺: E° = +0.15 V, ΔG° = -28.9 kJ, spontaneousThe +1 oxidation state is the most stable state for Tl, but it is not as common for Ga, because the disproportionation reaction for the formation of Tl⁺³ is non-spontaneous, while it is spontaneous for Ga³⁺_.
• C. Tl⁺: E° = +2.59 V, ΔG° = -250 kJ, spontaneousGa⁺: E° = -1.15 V, ΔG° = +28.9 kJ, non-spontaneousThe +1 oxidation state is the most stable state for Tl, but it is not as common for Ga, because the disproportionation reaction for the formation of Tl⁺³ is spontaneous, while it is non-spontaneous for Ga³⁺_.
• D. Tl⁺: E° = +2.99 V, ΔG° = -153 kJ, spontaneousGa⁺: E° = -1.25 V, ΔG° = +33.9 kJ, non-spontaneousThe +1 oxidation state is the most stable state for Tl, but it is not as common for Ga, because the disproportionation reaction for the formation of Tl⁺³ is spontaneous, while it is non-spontaneous for Ga³⁺_.

Answer: (B)