As we saw earlier, the mass
of metal deposited in an elecroplating cell is directly proportional
to the number of electrons pumped through the circuit. The number of
electrons are represented by **charge**. Charge is measured in units
called **coulombs(Q).**

Charge = current(amps) X time(seconds)

Q = I X t

It is found that

**"One mole of electrons
produce 96,500 coulomb of charge". **The
charge on one mole of electrons is called a *faraday. *

1 faraday = 96,500 coulomb / mol.

We can now calculate the charge on any given number of mole
of electrons.

eg. 3 mole of electrons will have a charge of (3 X 96,500) =289,500C

How can we use this information?

Example .

A silver plating cell operates for 15 minutes at a current of 20.0A.
What mass of silver is deposited at the cathode?

Step 1 Calculate the charge passed through the cell during the 15 minute
period.

*Q =
I X t*

Q = 20.0 X (15 X 60)s = 18,000C

(time must be expressed in seconds)

Step 2 Calculate
the mole of electrons passed through the circuit.

*mole
= 18,000C/96,500C/mol = 0.187 mole.*

Step 3 Calculate
the mass of silver

Ag^{+}_{(aq)} + e => Ag_{(s)}

According to the equation
above 0.187 mole of electrons will produce 0.187 mole of silver.

The mass of silver is therefore 0.187 X 107.9 = 20.13grams.