Calculate the mass of each electrode after 10.0 h.

Question

For the problem below I am unable to solve the last part. This is what I got for the questions prior that relate to the problem:

A zinc-copper battery is constructed as follows.

Zn | Zn²⁺ (0.15 M) || Cu²⁺ (2.53 M) | Cu

The mass of each electrode is 198 g.

(a) Calculate the cell potential when this battery is first connected. (Assume a standard temperature of 25°C.)

I got 1.14V.

(b)

Calculate the cell potential after 10.4 A of current has flowed for 10.0 h. (Assume each half-cell contains 1.00 L of solution).

I got 1.1V

(c)

Calculate the mass of each electrode after 10.0 h.

I do not know how to solve for the Zn electrode (in g) and the Cu electrode (in g).

Answer 1

Not sure if this is correct, but here is my best attempt. Hopefully someone else with more knowledge of electrochemistry will weigh in.

1 Coulomb (C) = 1 amp-sec

10 hours x 60 min/hour x 60 sec/min = 36,000 sec

36,000 sec x 10.4 amp = 374,400 amp-sec = 374,400 C

374,400 C x 1 mol electrons/96,500 C = 3.88 moles of electrons

3.88 moles electrons x 1 mol Zn or Cu/2 moles electrons = 1.94 moles of Zn or Cu

Zn: 1.94 mol Zn x 65.4 g/mol = 127 g Zn

Cu: 1.94 mol Cu x 63.5 g/mol = 123 g Cu

mass of Cu electrode = 198 g + 123 g = 321 g

mass of Zn electrode = 198 g - 127 g = 71 g