Question

1)

A Cu/Cu2+ concentration cell has a voltage of 0.21 V at 25 ∘C. The concentration of Cu2+ in one of the half-cells is 1.5×10⁻³ M .

What is the concentration of Cu2+ in the other half-cell?

Express your answer using two significant figures.

2)

Galvanized nails are iron nails that have been plated with zinc to prevent rusting. The relevant reaction is

Zn2+(aq)+2e−→Zn(s)

For a large batch of nails, a manufacturer needs to plate a total zinc mass of 1.80 kg on the surface to get adequate coverage.

How many moles of zinc are in 1.80 kg of zinc?

Express your answer to three significant figures and include the appropriate units.

3)

Part A

What mass of Cu(s) is electroplated by running 20.0 A of current through a Cu2+(aq) solution for 4.00 h?

Part B

How many minutes will it take to electroplate 30.1 g of gold by running 5.00 A of current through a solution of Au+(aq)?

Answer 1

1) Ecell = 0.0591/nlog(C2/c1)

       0.21 = (0.0591/2)log(0.0015/c1)

     C1 = 1.17*10^10^-10 M

2) no of mol of Zn = (1.8*10^3)/65.38 = 27.53 mol

3) W = Zit

   equivalent weight of Cu (E) = 65.38/2 = 32.69 g/equi

w = (32.69/96500)*20*4*60*60 = 97.56 grams

4) Part B

W = ZIt

z = E/F

E = equivalent mass of Au = 197/1 = 197 g/equi

F = 96500 C

w = 30.1 grams

30.1 = (197/96500)*5*t

t = 2948.9 sec

   = 49.15 min