13. Write the following balanced reactions using cell notation. Use platinum as an inert electrode, if needed. (a) Mg (s) + Ni2 + (aq) ⟶ Mg2 + (aq) + Ni (s) (b) 2Ag + (aq) + Cu (s) ⟶ Cu2 + (aq) + 2Ag (s) (c) Mn (s) + Sn (NO3) 2 (aq) ⟶ Mn (NO3) 2 (aq) + Au (s) (d) 3CuNO3 (aq) + Au (NO3) 3 (aq) ⟶ 3Cu (NO3) 2 (aq) + Au (s)

A) Mg ₍s₎ | Mg²⁺₍aq₎║Ni²⁺₍aq₎ | Ni₍s₎

B) Cu₍s₎ | Cu²⁺₍aq₎║ Ag⁺ | Ag⁰₍s₎

C) Cu₍s₎ | Cu²⁺₍aq₎║ Ag⁺ | Ag⁰₍s₎

D) Pt₍s₎ | CuNO₃₍ aq₎, Cu (NO₃) ₂₍aq₎ ║ Au (NO₃) ₃₍aq₎ | Au₍s₎

Explanation:

A) Mg + Ni²⁺ → Mg²⁺ + Ni

Mg⁰→ Mg²⁺ + 2e⁻ oxidation anode

Ni²⁺ + 2e⁻ → Ni⁰ reduction cathode

Mg ₍s₎ | Mg²⁺₍aq₎║Ni²⁺₍aq₎ | Ni₍s₎

anode salt bridge cathode

B) 2 Ag⁺₍aq₎ + Cu₍s₎ → Cu²⁺₍aq₎ + 2 Ag₍s₎

2 Ag⁺ + 2e⁻ → 2 Ag⁰ cathode

Cu → Cu²⁺ + 2e⁻ anode

Cu₍s₎ | Cu²⁺₍aq₎║ Ag⁺ | Ag⁰₍s₎

anode salt bridge cathode

C) Mn ₍s₎ + Sn (NO₃) ₂ ₍aq₎ → Mn (NO₃) ₂ ₍aq₎ + Au₍s₎

Mn⁰ → Mn²⁺ + 2e⁻ anode

Sn²⁺ + 2e⁻ → Sn⁰₍s₎ cathode

Mn₍s₎ | Mn (NO₃) ₂ ₍aq₎ ║ Sn (NO₃) ₂ ₍aq₎ | Sn₍s₎

anode salt bridge cathode

D) 3CuNO₃₍ aq₎ + Au (NO₃) ₃₍aq₎ → 3Cu (NO₃) ₂₍aq₎ + Au₍s₎

3Cu⁺ → 3Cu²⁺ + 3e⁻ anode

Au³⁺ + 3e⁻ → Au⁰ cathode

Pt₍s₎ | CuNO₃₍ aq₎, Cu (NO₃) ₂₍aq₎ ║ Au (NO₃) ₃₍aq₎ | Au₍s₎

anode salt bridge cathode

Semi-reactions are noted to determine oxidation and reduction. The oxidation reaction occurs at the anode and the reduction reaction at the cathode. In the case of subsections a, b, c the electrodes may be the solid metal, while in the case d the species are in an accusative medium and require the platinum electrode.