Laws of Electrolysis — Prelims Strategy

Prelims Strategy

To excel in NEET questions on Faraday's Laws, a systematic approach is essential. Firstly, thoroughly understand the statements and mathematical forms of both Faraday's First Law ($m = ZIt$ or $m = (E/F)It$) and Second Law ($m_1/m_2 = E_1/E_2$).

Memorize the value of the Faraday constant ($96500,\text{C/mol}$). For numerical problems, always start by identifying the given quantities and the unknown. Pay close attention to units; convert time to seconds and ensure current is in Amperes.

The most critical step is correctly determining the valency factor ($n$) for the substance undergoing deposition or liberation. This requires writing out the balanced half-reaction at the electrode. For example, $Cu^{2+} \to Cu$ means $n=2$, while $Ag^+ \to Ag$ means $n=1$.

An incorrect valency factor will lead to an incorrect equivalent weight and thus a wrong answer. When dealing with series connections, remember that the same quantity of electricity passes through all cells.

Practice a variety of problems, including those calculating mass, current, time, equivalent weight, and volume of gases liberated at STP. Be wary of trap options that arise from common mistakes like incorrect unit conversions or wrong valency factors.