Question

Humphrey Davy wanted to test out his electrolysis experiment of sodium. He made 3 particular changes to his experiment.
A. He increased current
B. He increased voltage
C. He increased the area of the electrode
What would be his observations?

• A. No difference in production of sodium in all cases as compared to before changing.
• B. Decreased production of sodium in all cases.
• C. Increased rate of production in case A and decreased rate of production in case B and no change in case C.
• D. Increased rate of production of sodium in all cases.

Answer 1

The correct option is D Increased rate of production of sodium in all cases.


Davy would find all the changes would lead to an increased rate of production of sodium. This can either be remembered as a factor affecting electrolysis or as we would soon see, it can be explained using Faraday's first law of electrolysis.
Increasing the current passed through the electrolyte would increase the rate at which the electrolysis reaction happens because more number of electrons are passed in a unit time. This would mean that a higher number of oxidation and reduction reactions are happening within a unit time.
Increasing the voltage would lead to an increase in the current passed, by Ohm's law since R is remaining constant.
(Ohm's law states that V = IR)
To answer how the dimension of an electrode would lead to an increase in the rate of electrolysis, let us look at the relation between Resistance and Area
$R=\frac{\rho \ast l}{A}$
Here you can observe that an increase in area would lead to a decrease in resistance. Decreasing the resistance keeping the voltage constant would mean an increase in current passed through. This would, in turn, lead to an increase in the rate of electrolysis as discussed.