Question

Consider the following reaction :

2Ag⁺ + C₆H₁₂O₆ + H₂O → 2Ag(s) + C₆H₁₂O₇ + 2H⁺

When ammonia is added to the solution, pH is raised to 11. Which half-cell reaction is affected by pH and by how much ?

Ag⁺ + e^– → Ag; $E_{red}^{º}$ = 0.8 V

C₆H₁₂O₆ + H₂O → C₆H₁₂O₇ + 2H⁺ + 2e^– ;

$E_{red}^{º}$ = – 0.05 V

Ag(NH₃)₂⁺ + e^–→ Ag(s) + NH₃ ;

$E_{red}^{º}$ = 0.337 V

• A. E_oxid. Will increase by a factor 0.65 from $E_{oxid.}^{º}$
• B. E_oxid. Will decrease by a factor of 0.65 from $E_{oxid.}^{º}$
• C. E_red will increase by a factor of 0.65 from $E_{red}^{º}$
• D. E_red. Will decrease by a factor of 0.65 from

Answer 1

Answer: (A)

E_oxid. Will increase by a factor 0.65 from $E_{oxid.}^{º}$

Answer 2

As ammonia is — added the concentration of H⁺

decreases, thus oxidation potential increases by 0.65.