applications of thermodynamics summary

Question

Magnesium metal will react with an acid (hydrogen ions) in a reaction.

a. write the cell diagram for this reaction

b. calculate E°_cell

Mg⁺² (aq) + 2 e^-1 --> Mg (s) E° = -2.37 V

2 H⁺¹ (aq) + 2 e^-1 ---> H₂ (g) E° = 0.00 V

c. Which species is oxidized in the reaction

Answer 1

a)

Cell diagram: Mg(s) | Mg²⁺(aq) || H⁺(aq) | H₂(g)

b)

Mg⁺² (aq) + 2 e^-1 --> Mg (s) E° = -2.37 V (anode)

2 H⁺¹ (aq) + 2 e^-1 ---> H₂ (g) E° = 0.00 V (cathode)

Eº_cell = Eº_cat - Eº_anode = 0 - (-2.37) = +2.37 V

c)

Oxidation takes place a the anode, so Mg is oxidized. The overall reaction looks like this...

Mg(s) + 2H⁺(aq) ==> Mg²⁺(aq) + H₂(g)

Mg is oxidized

H⁺ is reduced