JEE Main 2021 · ChemistryNumerical answerNumerical valueMediumCalculation

JEE Main 25 February 2021, Shift 1, Chemistry Q55

Question 55 of 90 in this shift, Chemistry question 25 of 30, Section B.

In basic medium

\mathrm{CrO_4^{2-}}

oxidises

\mathrm{S_2O_3^{2-}}

to form

\mathrm{SO_4^{2-}}

and itself changes into

\mathrm{Cr(OH)_4^{-}}

. The volume of 0.154 M

\mathrm{CrO_4^{2-}}

required to react with 40 mL of 0.25 M

\mathrm{S_2O_3^{2-}}

is ________ mL. (Rounded-off to the nearest integer)

Official answer

173

NTA final key.

Chapter: Redox Reactions
Topic: Redox Reactions
Idea tested: Law of Chemical Equivalence in Redox

Same idea in other shifts

Asked 6× in all

4 Apr 2026, Shift 1 · Q56In order to oxidise a mixture of $1$ mole each of $\mathrm{FeC_2O_4}$ , $\mathrm{Fe_2(C_2O_4)_3}$ , $\mathrm{FeSO_4}$ and…MediumSingle correct
4 Apr 2024, Shift 1 · Q87Only 2 mL of $\mathrm{KMnO_4}$ solution of unknown molarity is required to reach the end point of a titration of 20 mL of oxalic acid (2…MediumNumerical value
27 Jul 2022, Shift 1 · Q8120 mL of 0.02 M $\mathrm{K_2Cr_2O_7}$ solution is used for the titration of 10 mL of $\mathrm{Fe^{2+}}$ solution in the acidic medium. The…EasyNumerical value
17 Mar 2021, Shift 1 · Q5715 mL of aqueous solution of $\mathrm{Fe^{2+}}$ in acidic medium completely reacted with 20 mL of 0.03 M aqueous $\mathrm{Cr_2O_7^{2-}}$ .…MediumNumerical value
4 Sep 2020, Shift 1 · Q49A 20.0 mL solution containing 0.2 g impure $\mathrm{H_2O_2}$ reacts completely with 0.316 g of $\mathrm{KMnO_4}$ in acid solution. The…MediumNumerical 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. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.