JEE Main · 2019 · Shift-ImediumEC-023

For the cell Zn(s)|Zn2+(aq)\|Mx+(aq)|M(s), different half cells and their standard electrode potentials are given…

Electrochemistry · Class 12 · JEE Main Previous Year Question

Question

For the cell Zn(s)∣Zn2+(aq)∥Mx+(aq)∣M(s)\mathrm{Zn(s)|Zn^{2+}(aq)\|M^{x+}(aq)|M(s)}, different half cells and their standard electrode potentials are given below:

| Mx+(aq)/M(s)\mathrm{M^{x+}(aq)/M(s)} | Au3+(aq)/Au(s)\mathrm{Au^{3+}(aq)/Au(s)} | Ag+(aq)/Ag(s)\mathrm{Ag^+(aq)/Ag(s)} | Fe3+(aq)/Fe2+(aq)\mathrm{Fe^{3+}(aq)/Fe^{2+}(aq)} | Fe2+(aq)/Fe(s)\mathrm{Fe^{2+}(aq)/Fe(s)} | |---|---|---|---|---| | E°Mx+/ME°_{\mathrm{M^{x+}/M}} (V) | 1.40 | 0.80 | 0.77 | −0.44 |

If E°Zn2+/Zn=−0.76 VE°_{\mathrm{Zn^{2+}/Zn}} = -0.76\ \mathrm{V}, which cathode will give a maximum value of E°cellE°_{\text{cell}} per electron transferred?

Options
  1. a

    Ag+/Ag\mathrm{Ag^+/Ag}

    ✓
  2. b

    Fe3+/Fe2+\mathrm{Fe^{3+}/Fe^{2+}}

  3. c

    Au3+/Au\mathrm{Au^{3+}/Au}

  4. d

    Fe2+/Fe\mathrm{Fe^{2+}/Fe}

Correct Answera

Ag+/Ag\mathrm{Ag^+/Ag}

Detailed Solution

Strategy: The question asks for the maximum value of Ecell∘E^\circ_{\text{cell}} per electron transferred. This is defined as (Ecathode∘−Eanode∘)/n(E^\circ_{\text{cathode}} - E^\circ_{\text{anode}}) / n, where nn is the number of electrons in the reduction half-reaction.

Step 1: Setup calculations for all half-cells Anode is Zinc: Eanode∘=−0.76 VE^\circ_{\text{anode}} = -0.76\text{ V}. Formula: Value=Ecathode∘−(−0.76)n\text{Value} = \frac{E^\circ_{\text{cathode}} - (-0.76)}{n}

  1. \ceAu3+/Au\ce{Au^{3+}/Au}: 1.40+0.763=2.163=0.72\frac{1.40 + 0.76}{3} = \frac{2.16}{3} = 0.72
  2. \ceAg+/Ag\ce{Ag^+/Ag}: 0.80+0.761=1.56\frac{0.80 + 0.76}{1} = 1.56 (Maximum)
  3. \ceFe3+/Fe2+\ce{Fe^{3+}/Fe^{2+}}: 0.77+0.761=1.53\frac{0.77 + 0.76}{1} = 1.53
  4. \ceFe2+/Fe\ce{Fe^{2+}/Fe}: −0.44+0.762=0.16\frac{-0.44 + 0.76}{2} = 0.16

Step 2: Conclusion The silver electrode gives the highest potential per electron.

Answer: (a) \ceAg+/Ag\boxed{\text{Answer: (a) } \ce{Ag^+/Ag}}

Practice this question with progress tracking

Want timed practice with adaptive difficulty? Solve this question (and hundreds more from Electrochemistry) inside The Crucible, our adaptive practice platform.

Practice in The Crucible →Browse Electrochemistry chapter →

More JEE Main Electrochemistry PYQs

2025medium

Match List-I with List-II: List-I (Applications) | List-II (Batteries/Cell) (A) Transistors | (I) Anode – Zn/Hg; Cathode – HgO + C (B) Hearing aids | (II) Hydrogen fuel cell (C) Invertors | (III)…

2024easy

One of the commonly used electrode is calomel electrode. Under which of the following categories, calomel electrode comes?

2024easy

How can an electrochemical cell be converted into an electrolytic cell?

2024medium

For the electrochemical cell, if E°(M2+/M) = 0.46\ V and E°(X/X2-) = 0.34\ V. Which of the following is correct?

2024easy

The reaction: {1}{2}{H_{2(g)}} + {AgCl_{(s)}} {H^+_{(aq)}} + {Cl^-_{(aq)}} + {Ag_{(s)}} occurs in which of the following galvanic cell:

View all 65 Electrochemistry PYQs →
For the cell Zn(s)|Zn2+(aq)\|Mx+(aq)|M(s), different half cells and their standard electrode… (JEE Main 2019) | Canvas Classes