Determine the quantity of electricity used when a current of 0.20 amperes is passed through an electrolytic cell for 60 minutes.

Analyze the question: You are asked for the quantity of electricity (charge, Q) that flows when a current of 0.20 A passes for 60 minutes.

Concept: Quantity of electricity is current multiplied by time:

Q = I × t

• Q is measured in coulombs (C)
• I is measured in amperes (A)
• t must be in seconds (this is where many students lose marks!)

Solution:

1. Convert time to seconds: t = 60 minutes × 60 s/min = 3600 s

2. Substitute into the formula: Q = 0.20 × 3600 Q = 720 C

Common mistakes:

• Using 60 directly gives 0.20 × 60 = 12 C (option A, a trap).
• Using 30 minutes by mistake gives 360 C (option C).

Tip: In every electrolysis question, convert minutes or hours to seconds first. Remember "Q = It, time in seconds". Also, 1 Faraday = 96,500 C, so you can later use Q to find the mass of a substance deposited with m = (Q × M)/(n × 96500).

Answer: D. 720 C