20. Electrochemistry

Determine [Fe²⁺] for the following galvanic cell at 25ºC if given [Sn²⁺] = 0.072 M, [Fe³⁺] = 0.0219 M, and [Sn⁴⁺] = 0.00345 M. 

Sn²⁺ (aq) + 2 Fe³⁺ (aq)  ⇌. Sn⁴⁺ (aq) + 2 Fe²⁺ (aq)     E_cell = + 0.68 V

Standard Reduction Potentials

Sn⁴⁺ (aq) + 2 e^–  →. Sn²⁺ (aq)      E°_red = + 0.151 V

Fe³⁺ (aq) + e^–  →  Fe²⁺ (aq)         E°_red = + 0.771 V

If [Br^–] = 0.010 M and [Al³⁺] = 0.022 M, predict whether the following reaction would proceed spontaneously as written at 25ºC:

Al (s) + Br₂ (l) ⇌ Al³⁺ (aq) + Br^– (aq)

Standard Reduction Potentials

Al³⁺ (aq) + 3 e^– → Al (s)       E°_red = –1.66 V

Br₂ (l) + 2 e^– → 2 Br^– (aq)     E°_red = +1.09 V

______________________ accelerates the rusting process.