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Saturday, 31 October

JEE Main 2025 · ChemistryNumerical answerNumerical valueHardMulti-step

JEE Main 7 April 2025, Shift 1, Chemistry Q71

Question 71 of 75 in this shift, Chemistry question 21 of 25, Section B.

1 Faraday electricity was passed through Cu2+\mathrm{Cu^{2+}} (1.5 M, 1 L) /Cu and 0.1 Faraday was passed through Ag+\mathrm{Ag^+} (0.2 M, 1 L)/Ag electrolytic cells. After this the two cells were connected as shown below to make an electrochemical cell. The emf of the cell thus formed at 298 K is __________ mV (nearest integer) Given : ECu2+/Cu∘=0.34E^\circ_{\mathrm{Cu^{2+}/Cu}} = 0.34 V EAg+/Ag∘=0.8E^\circ_{\mathrm{Ag^+/Ag}} = 0.8 V 2.303RTF=0.06\frac{2.303RT}{F} = 0.06 V

The figure, in words

Electrochemical cell: Cu electrode dipping in Cu2+(aq) beaker (left) and Ag electrode dipping in Ag+(aq) beaker (right), joined by a salt bridge; the two electrodes are connected through a galvanometer/meter at the top.

Official answer

400

NTA final key.

Chapter
Electrochemistry
Topic
Nernst Equation
Idea tested
Full Cell Nernst Equation

Same idea in other shifts

Asked 12× in all
  1. 4 Apr 2026, Shift 2 · Q73An electrochemical cell, consist of the following two redox couples, Mx+(aq)/M(s)\mathrm{M^{x+}(aq)/M(s)} [Ered⊖=+0.15 V][E^\ominus_{red}=+0.15\ \mathrm{V}] and…HardNumerical value
  2. 5 Apr 2026, Shift 2 · Q57One half cell in a voltaic cell is constructed by dipping silver rod in AgNO3\mathrm{AgNO_3} solution of unknown concentration, other half…MediumSingle correct
  3. 8 Apr 2024, Shift 2 · Q63The emf of cell Tl ∣ Tl+(0.001 M) ∣∣ Cu2+(0.01 M) ∣ Cu\mathrm{Tl\,|\,Tl^+(0.001\,M)\,||\,Cu^{2+}(0.01\,M)\,|\,Cu} is 0.83 V at 298 K. It could be increased by :MediumSingle correct
  4. 25 Jul 2022, Shift 1 · Q84The cell potential for Zn∣Zn2+(aq)∥Snx+∣ Sn\mathrm{Zn|Zn^{2+}(aq)\|Sn^{x+}|\,Sn} is 0.8010.801 V at 298 K. The reaction quotient for the above reaction is…MediumNumerical value
  5. 29 Jul 2022, Shift 2 · Q84For a cell, Cu(s)∣Cu2+(0.001M)∣∣Ag+(0.01M)∣Ag(s)\mathrm{Cu(s) \mid Cu^{2+}(0.001M) \mid\mid Ag^{+}(0.01M) \mid Ag(s)} the cell potential is found to be 0.43 V at 298 K. The…MediumNumerical value
  6. 24 Jun 2022, Shift 1 · Q84The cell potential for the following cell Pt ∣H2(g)∣H+(aq)∥ Cu2+(0.01 M)∣Cu(s)\mathrm{Pt\,|H_2(g)|H^+(aq)\|\ Cu^{2+}(0.01\ M)|Cu(s)} is 0.576 V at 298 K. The pH of the…MediumNumerical value
  7. 26 Aug 2021, Shift 2 · Q56For the galvanic cell, Zn(s)+Cu2+\mathrm{Zn(s) + Cu^{2+}} (0.02 M) →Zn2+\rightarrow \mathrm{Zn^{2+}} (0.04 M) +Cu(s)+ \mathrm{Cu(s)}, Ecell\mathrm{E_{cell}}…MediumNumerical value
  8. 26 Feb 2021, Shift 2 · Q57Emf of the following cell at 298 K in V is x×10−2x \times 10^{-2}. Zn∣Zn2+\mathrm{Zn|Zn^{2+}} (0.1 M)∥\|Ag+\mathrm{Ag^+} (0.01 M)∣|Ag The value of…MediumNumerical value

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.