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Saturday, 31 October

JEE Main · Chemistry · Environmental Chemistry

Drinking Water Standards: Fluoride Limits

JEE Main asked Drinking Water Standards: Fluoride Limits 3 times in 3 of the 108 shifts Lumi analysed, in 2021, 2022 and 2024. It belongs to Environmental Chemistry (Chemistry). The longest wait between two years asking it was 2 years.

Updated 2026-10-24

Times asked
3
in 3 shifts
Years
3 of 8
First asked
2021
last in 2024
Pattern
Comes in cycles
across the analysed shifts

Questions on this idea a shift, by year

2017–2026. Asked in 2021, 2022 and 2024. Years differ in how many shifts Lumi analysed, so each year is scaled to one shift of 25 Chemistry questions.

00.050.10’170’200.03’210.03’220’230.05’240’250’26

Raw count: 2017: 0 in 1 shift · 2020: 0 in 12 shifts · 2021: 1 in 24 shifts · 2022: 1 in 24 shifts · 2023: 0 in 12 shifts · 2024: 1 in 18 shifts · 2025: 0 in 8 shifts · 2026: 0 in 9 shifts.

Shift by shift

Each square is one analysed shift, in date order. Open a filled one for that paper.

  • 20260 of 9
  • 20250 of 8
  • 20241 of 18
  • 20230 of 12
  • 20221 of 24
  • 20211 of 24
  • 20200 of 12
  • 20170 of 1

Asked in that shift More than once Not asked

How JEE Main framed it

Single correct is the usual form. Skill tested: recall.

  • Identify formula of compound
  • Match list on pollutants and effects

Difficulty

Easy 0Medium 3Hard 0

Every question was multiple choice.

Every question

All 3 questions

From the official JEE Main shift papers, newest first. Open one for the full question, the options and the official answer.

  1. 9 Apr 2024, Shift 1 · Q67The F−\mathrm{F^-} ions make the enamel on teeth much harder by converting hydroxyapatite (the enamel on the surface of teeth) into much…MediumSingle correct
  2. 25 Jul 2022, Shift 2 · Q72Match List I with List II. List I | List II A. Sulphate | I. Pesticide B. Fluoride | II. Bending of bones C. Nicotine | III. Laxative…MediumMatch the list
  3. 26 Aug 2021, Shift 1 · Q40The conversion of hydroxyapatite occurs due to presence of F−\mathrm{F^-} ions in water. The correct formula of hydroxyapatite is :MediumSingle correct

Shifts: 26 Aug 2021, Shift 1, 25 Jul 2022, Shift 2, 9 Apr 2024, Shift 1.

Same topic

Other ideas in Environmental Chemistry

Environmental Chemistry has 19 ideas JEE Main has asked; 15 of them came up in more than one question. The 12 most asked are below.

Topic analysisChapter analysisAll repeated ideas