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Saturday, 10 October

JEE Main 2021 · ChemistryMultiple choiceAssertion–reasonEasyConceptual

JEE Main 3 August 2021, Shift 2, Chemistry Q41

Question 41 of 90 in this shift, Chemistry question 11 of 30, Section A.

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A : Fluoride ion concentration above 2 ppm causes brown mottling of teeth. Reason R : The presence of fluoride ions in drinking water converts hydroxyapatite (tooth enamel) into fluorapatite. In the light of the above statements, choose the most appropriate answer from the options given below
  1. (1)Both A and R are correct and R is the correct explanation of AOfficial answer
  2. (2)Both A and R are correct but R is NOT the correct explanation of A
  3. (3)A is correct but R is NOT correct
  4. (4)A is NOT correct but R is correct.

Official answer

Option 1

NTA final key.

Chapter
Environmental Chemistry
Topic
Environmental Chemistry
Idea tested
Fluoride Limits in Drinking Water

Same idea in other shifts

Asked 2× in all
  1. 2 Apr 2017 (offline) · Q44A water sample has ppm level concentration of following anions F−=10\mathrm{F^-}=10 ; SO42−=100\mathrm{SO_4^{2-}}=100 ; NO3−=50\mathrm{NO_3^-}=50 The…EasySingle correct

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. Lumi analyses 42 of the 174 JEE Main shifts held from 2017 to 2026.