Question

An electrolytic cell is composed of Cu and Zn. A current of 9.65 A is drawn from a cell for 1 hour. Then the loss in mass at anode and gain in mass at the cathode, respectively could be:
A. 11.77 g, 11.43 g
B. 11.77 g, 10 g
C. 22.86 g, 23.54 g
D. 23.54 g, 22.86 g

Answer 1

Hint: An electrochemical cell is a device capable of either generating electrical energy from chemical reactions or using electrical energy to cause a chemical reaction. An electrolytic cell is an electrochemical cell that drives a non-spontaneous redox reaction through the application of electrical energy. They are often used to decompose chemical compounds, in a process called electrolysis.

Complete step by step answer:
The mass deposited on the cathode or the mass lost at the anode is given by the expression:
$W = \dfrac{{I \times t \times M}}{{nF}}$
Where w is the weight lost at the anode or the weight gained at the cathode.
I is the amount of current passed through the cell
T is the time for which the current is being passed (in seconds)
M is the molar mass of the element of anode or cathode
N is the number of electrons involved in the redox reaction
F is Faraday’s constant which is equal to 96500.
Now, let us first calculate the mass lost at anode using the above reaction:
For zinc, the molar mass is 65.38 g/mol. And the number of electrons involved in the redox reaction between zinc and copper is 2. Therefore putting all the values in the equation we have:
$W = \dfrac{{9.65 \times 3600 \times 65.5}}{{2 \times 96500}}$
Which gives $W = 11.77g$
Therefore, 11.77 g of Zn is lost at the anode.
Let us find the amount of Cu deposited on the cathode:
For copper, the molar mass is 63.5 g/mol, putting all the values we have:
$W = \dfrac{{9.65 \times 3600 \times 63.5}}{{2 \times 96500}}$
Therefore, $W = 11.43g$
It means that 11.43 g of Cu will be deposited on the cathode.

So, the correct answer is Option A.

Note:
Faraday gave some very important law regarding electrolysis:
The amount of chemical change produced by the current at an electrode-electrolyte boundary is proportional to the quantity of current passed.
The amounts of chemical change produced by the same quantity of electricity in different substances are proportional to their equivalent weights.