Physics 2014 JAMB Past Questions - Question 46: Calculate the mass of the copper deposited during electrolysis when a current of 4A passes through a copper salt for 2 hours .

Correct Answer

B

Explanation

To calculate the mass of copper deposited during electrolysis when a current of 4 amperes (A) passes through a copper salt for 2 hours, you can use Faraday's laws of electrolysis. Faraday's First Law states that the mass of a substance deposited during electrolysis is directly proportional to the amount of charge passed through the electrolyte. The formula to calculate the mass of the substance deposited is:

Mass (m) = (Q * M) / (n * F)

Where:
- m is the mass of the substance deposited (in grams).
- Q is the charge passed through the electrolyte (in coulombs).
- M is the molar mass of the substance (in grams per mole).
- n is the number of moles of the substance.
- F is Faraday's constant, which is approximately 96,485 C/mol.

First, you need to determine the number of moles of copper deposited. You can use the equation:

n = (Q) / (2 * F)

Where:
- Q is the charge passed through the electrolyte, which is equal to the current (I) multiplied by the time (t).
- I is the current in amperes (4 A).
- t is the time in seconds (2 hours converted to seconds).

Q = I * t
Q = 4 A * 2 hours * 3600 s/hour = 28,800 C

Now, calculate the number of moles (n):

n = 28,800 C / (2 * 96,485 C/mol) ≈ 0.149 moles

The molar mass of copper (Cu) is approximately 63.55 g/mol.

Now, you can calculate the mass of copper deposited (m):

m = (0.149 moles * 63.55 g/mol) / 1 ≈ 9.46 grams

So, approximately 9.46 grams of copper will be deposited during the electrolysis when a current of 4 amperes passes through the copper salt for 2 hours.