JEE Main 2022 · 26 June · morning · Single correct · +4 / −1
The ( (∂ E)/(∂ T) )_P of different types of half cells are as follows:
(Where E is the electromotive force)
Which of the above half cells would be preferred to be used as reference electrode?
| A | B | C | D |
|---|---|---|---|
| 1 × 10⁻⁴ | 2 × 10⁻⁴ | 0.1 × 10⁻⁴ | 0.2 × 10⁻⁴ |
- (a) A
- (b) B
- (c) C
- (d) D
Answer and solution
Answer (c) C
Solution
Chemistry ma’am · 3 steps
A reference electrode must hold its potential steady, so pick the one that drifts least with temperature.
- What a reference needs. A reference electrode is the fixed point against which every other potential is measured. Its own potential must stay as constant as possible, even when the lab temperature changes a little.
- Read the coefficient. ((∂ E)/(∂ T))_P tells you how many volts the potential shifts per kelvin. The smaller this value, the more temperature-stable the electrode.
Half cell ((∂ E)/(∂ T))_P in V K⁻¹ Shift for a 10 K change A 1 × 10⁻⁴ 1 × 10⁻³ V B 2 × 10⁻⁴ 2 × 10⁻³ V C 0.1 × 10⁻⁴ = 1 × 10⁻⁵ 1 × 10⁻⁴ V, smallest D 0.2 × 10⁻⁴ = 2 × 10⁻⁵ 2 × 10⁻⁴ V - So. Half cell C has the smallest temperature coefficient, so its potential changes the least and it is the best choice for a reference electrode, option (c).
The idea to keep. A good reference electrode has a steady potential. When you are given ((∂ E)/(∂ T))_P values, the smallest one marks the most reliable reference.
Answer from the NTA final answer key. Solution by PrepWiser.