Faraday s first law of electrolysis can be expressed mathematically as

Analyze the question: Faraday's first law of electrolysis relates the mass of a substance deposited or liberated at an electrode to the quantity of electricity passed through the electrolyte.

Concept: The law says that the mass (m) of a substance liberated during electrolysis is directly proportional to the quantity of electricity (Q) passed:

m ∝ Q

Quantity of electricity is current multiplied by time:

Q = I × t

Substituting this into the proportionality gives:

m ∝ It

This can also be written as m = ZIt, where Z is the electrochemical equivalent of the substance.

Checking the options:

• A. m = I/it is wrong. It is dimensionally meaningless and is not Faraday's law.
• B. m ∝ it is correct. It is the mathematical statement of the first law.
• C. Q = it is a true relationship, but it only defines charge. It does not involve mass, so it is not the law.
• D. Q ∝ I/it is wrong.
• E. Q ∝ it is true, but it is trivial because Q = It by definition. It does not state the law, since mass is missing.

Answer: B. The first law links mass to the current and time, m ∝ It.

Exam tip: Faraday's first law is always about mass (m) and quantity of electricity (Q = It). If an option has m ∝ Q or m ∝ It, choose it. Options without m, like C and E, only describe charge.