Question

1. a process called “flash” electroplating, a current of 2.50 x 103 A passes through and electrolytic cell for 5.00 minutes. How many moles of electrons are driven through the cell?

Answer 1

During 5.00 minutes ($t=$ 5.00*60 = 300 seconds) a current $I$ of 2.50x10³ A passes through an electrolytic cell. This process transports the following charge $q$ :

$q = It = 2.50\cdot10^3\text{ A}\cdot300\text{ s} = 7.5\cdot10^5$ C.

According to the definition of the SI units, one coulomb corresponds exactly to 1/1.602176634x10^-19 elementary charges:

$N = \frac{q}{1.602176634\cdot10^{-19}} = 4.7\cdot10^{24}$ .

Finally, the number of the moles of electrons can be calculated as the ratio of the number of the electrons and the Avogadro constant:

$n(e^-) = \frac{N}{N_A} = \frac{4.7\cdot10^{24}}{6.02214076\cdot10^{23}\text{mol}^{-1}} = 7.77$ mol.

Answer: 7.77 mol of electrons is driven through the cell during "flash" electroplating.