Q27 · CSIR-NET Chemistry, December 2016
Paper: CSIR-NET December 2016 · Subject: Physical Chemistry · Chapter: Electrochemistry · Topic: Electrochemistry – General · Marks: 2 · Difficulty: Hard
Given \[ \text{(i)}\ \mathrm{Zn+4NH_3 \rightarrow Zn(NH_3)_4^{2+}+2e}, \quad E^{o}=1.03\,\mathrm{V} \]
\[ \text{(ii)}\ \mathrm{Zn \rightarrow Zn^{2+}+2e}, \quad E^{o}=0.763\,\mathrm{V} \]
the formation constant of the complex $\mathrm{Zn(NH_3)_4^{2+}}$ is approximately (a)$1 \times 10^{5}$
(b)$1 \times 10^{7}$
(c)$1 \times 10^{9}$
(d)$1 \times 10^{12}$
Answer
Answer: C ✓ checked by 4AB · confidence high
Explanation
Subtracting (ii) from (i): Zn²⁺ + 4NH₃ → [Zn(NH₃)₄]²⁺ with E° = 1.03 − 0.763 = 0.267 V. log Kf = 2 × 0.267/0.0591 ≈ 9.0, so Kf ≈ 10⁹ (c).
Study loop for Electrochemistry
· Browse this chapter in the app