How many grams of cu will be deposited from a

1. How many grams of Cu will be deposited from a solution of CuSO
4
by a current of 1.5 A flowing for
2.0 hours?
2. Find the mass of copper produced at the cathode by passing a current of 3.00 A through aqueous
copper sulfate for exactly 2 hours.
3. A constant current is passed through an electrolytic cell containing molten MgCl
2
for 18 hours.
If 4.8 x 10
5
g of chlorine are obtained, what is the current in amperes? (answer = 2.0 x 10
4
A)
4. Consider the electrolysis of CaCl
2
(l). How many grams of Ca (s) can be produced by passing 0.5 A
for 30 minutes?
5. How many faradays of electricity ( or moles of electrons) are required to produce:
(a) 0.84 dm
3
of oxygen gas from hydrogen sulfate (aq)
(b) 1.50 dm
3
of chlorine gas from NaCl (l)
(c) 6.0 g of tin from molten SnCl
2
.
6. How many hours would it take to produce 25.0 g of Cr from a solution of CrCl
3
by a current of 2.75 A?
Electroplating
In an electrolytic cell used for electroplating e.g. copper:
 the cathode should be the object that needs to be plated so that its negative charge attracts the
positive copper ions coming from the anode which then are reduced into copper atoms which leave the
solution and are deposited onto the object;
half-equation: Cu
2+
(aq) + 2e
-
 Cu (s)
 the electrolyte should be a solution of a copper salt such as copper nitrate or copper sulphate.
 the anode could be:
 carbon, in that case oxidation of water occurs producing oxygen gas
half-equation: H
2
O (l)  ½ O
2
(g) + 2H
+
(aq) + 2e
-
In addition to the cathode being coated with copper, the solution will become colourless and have
a lower pH.
 copper (this can be impure copper), in that case copper atoms should be oxidised into copper ions
which then go into the solutions; the electrons that have been released are attracted to the positive
terminal of the power supply
half-equation: Cu(s)  Cu
2+
(aq) + e
-