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Saturday, 31 October

JEE Main 2020 · ChemistryMultiple choiceDiagram basedMediumConceptual

JEE Main 4 September 2020, Shift 1, Chemistry Q27

Question 27 of 75 in this shift, Chemistry question 2 of 25.

ECu2+∣Cu∘=+0.34 VE^\circ_{\mathrm{Cu^{2+}|Cu}} = +0.34\ \mathrm{V} EZn2+∣Zn∘=−0.76 VE^\circ_{\mathrm{Zn^{2+}|Zn}} = -0.76\ \mathrm{V} Identify the incorrect statement from the options below for the above cell :

The figure, in words

Cell diagram: left beaker with Zn rod labelled '-ve' in '1M ZnSO4 soln.', right beaker with Cu rod labelled '+ve' in '1M CuSO4 soln.', joined by a 'Salt Bridge'. The rods are connected through a galvanometer; an external source labelled 'E_ext' (cell symbol) with a variable resistor/slider is connected across the two rods.
  1. (1)If Eext<1.1\mathrm{E_{ext}} < 1.1 V, Zn dissolves at anode and Cu deposits at cathode
  2. (2)If Eext=1.1\mathrm{E_{ext}} = 1.1 V, no flow of e−\mathrm{e^-} or current occurs
  3. (3)If Eext>1.1\mathrm{E_{ext}} > 1.1 V, e−\mathrm{e^-} flows from Cu to Zn
  4. (4)If Eext>1.1\mathrm{E_{ext}} > 1.1 V, Zn dissolves at Zn electrode and Cu deposits at Cu electrodeOfficial answer

Official answer

Option 4

NTA final key (Sep 2020).

Chapter
Electrochemistry
Topic
No close match in our taxonomy
Idea tested
No close match in our taxonomy

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.