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Saturday, 31 October

JEE Main 2020 · ChemistryMultiple choiceDiagram basedEasyDiagram reading

JEE Main 5 September 2020, Shift 1, Chemistry Q45

Question 45 of 75 in this shift, Chemistry question 20 of 25.

Identify the correct molecular picture showing what happens at the critical micellar concentration (CMC) of an aqueous solution of a surfactant ([shaded circle symbol] polar head; [wavy line symbol] non-polar tail ; [small dot symbol] water).

The figure, in words

Four beaker drawings labelled (A) to (D) as printed, each with a horizontal liquid-surface line and small dots for water. (A): shaded circles (heads) sit on the surface line with wavy tails pointing up above the line; no aggregate inside the liquid. (B): shaded circles above the surface line with wavy tails pointing down into the liquid; a small group of a few molecules inside the liquid with tails together and heads outward. (C): shaded circles above the surface line with tails pointing down into the liquid; a larger cluster inside the liquid with wavy tails pointing to the centre and shaded heads outward. (D): the surface line is drawn broken by short wavy tails pointing up, with the shaded heads just below the surface line in the liquid; a cluster inside the liquid with tails towards the centre and heads outward. The options 1 to 4 are printed only as (A), (B), (C), (D).
  1. (1)(A)
  2. (2)(B)
  3. (3)(C)
  4. (4)(D)Official answer

Official answer

Option 4

NTA final key (Sep 2020).

Chapter
Surface Chemistry
Topic
Colloids
Idea tested
Micelle Formation and CMC

Same idea in other shifts

Asked 5× in all
  1. 25 Jul 2022, Shift 2 · Q65For micelle formation, which of the following statements are correct ? A. Micelle formation is an exothermic process. B. Micelle formation…MediumOther
  2. 25 Jun 2022, Shift 1 · Q79Using very little soap while washing clothes, does not serve the purpose of cleaning of clothes, because :EasySingle correct
  3. 25 Jul 2021, Shift 1 · Q32Sodium stearate CH3(CH2)16COO−Na+\mathrm{CH_3(CH_2)_{16}COO^-Na^+} is an anionic surfactant which forms micelles in oil. Choose the correct statement for…MediumSingle correct
  4. 3 Sep 2020, Shift 2 · Q26An ionic micelle is formed on the addition of :MediumSingle correctHas a figure

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.