Question

Part A What mass of Cu(s) is electroplated by running 18.0 A of current through a Cu2+(aq) solution for 4.00 h? Express your answer to three significant figures and include the appropriate units.

Part B How many minutes will it take to electroplate 37.1 g of gold by running 5.00 A of current through a solution of Au+(aq)? Express your answer to three significant figures and include the appropriate units.

Answer 1

A)
charge passed,
Q = I*t
= 18.0 A * (4*60*60)s
= 259200 C

1 mol of electron = 96485 C

mol of electron passed = 259200/96485 = 2.686

2 mol of electron is required for each mol of Cu2+

mol of Cu electroplated = 2.686/2 = 1.343 mol

molar mass of Cu = 63.5 g/mol

mass of Cu= number of moles * molar mass
= 1.343 * 63.5
=85.3 g
Answer: 85.3 g

b)
moles of electron required = moles of gold
= mass/molar mass
= 37.1/197
=0.188 mol

charge passed = 0.188*96485 C = 18170.5 C

Now use:
Q = I*t
18170.5 = 5.00*t
t = 3634 s
= 60.6 minutes
Answer: 60.6 minutes