Learn

Friday, 9 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 6× 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. 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
  4. 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
  5. 25 Jul 2021, Shift 1 · Q58Consider the cell at 25∘^\circC Zn∣Zn2+(aq),(1 M) ∣∣ Fe3+(aq),Fe2+(aq)∣Pt(s)\mathrm{Zn|Zn^{2+}(aq),(1\ M)\,||\,Fe^{3+}(aq),Fe^{2+}(aq)|Pt(s)} The fraction of total iron present as…HardNumerical 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 42 of the 174 JEE Main shifts held from 2017 to 2026.