For a Cu-Zn Daniell cell, the emf is measured to be 1.10 V under standard conditions. If [Cu²⁺] = 1 M and [Zn²⁺] = 0.01 M at 298 K, the cell EMF becomes
A{'text': '+0.99 V', 'label': 'A'}
B{'text': '+1.10 V', 'label': 'B'}
C{'text': '+1.16 V', 'label': 'C'}
D{'text': '+1.22 V', 'label': 'D'}
Answer & Solution
Correct answer: C. {'text': '+1.16 V', 'label': 'C'}
1. Cell reaction: Zn + Cu²⁺ → Zn²⁺ + Cu, n = 2.
2. E = E° − (0.059/2) log ([Zn²⁺]/[Cu²⁺]) = 1.10 − 0.0295 × log(0.01).
3. log(0.01) = −2, so the correction is −0.0295 × (−2) = +0.059.
4. E ≈ 1.10 + 0.059 ≈ +1.159 V, closest to +1.16 V.
_Source: NCERT Class 12 Chemistry, Unit 3 "Electrochemistry", §3.3_
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