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Saturday, 31 October

JEE Main 2021 · ChemistryNumerical answerNumerical valueMediumCalculation

JEE Main 4 August 2021, Shift 2, Chemistry Q56

Question 56 of 90 in this shift, Chemistry question 26 of 30, Section B.

0.7 cm3\mathrm{cm^3} of compound A (molar mass = 70 g mol−1\mathrm{g\ mol^{-1}}, density = 1.024 g cm−3\mathrm{g\ cm^{-3}}) is dissolved in 1 dm3\mathrm{dm^3} of water. If the depression in freezing point of water is 0.02 o^{\mathrm{o}}C, the van't Hoff factor for the compound A is ________ × 10−2\times\ 10^{-2}. (Nearest integer) [Given : Kf\mathrm{K_f} for H2O\mathrm{H_2O} = 1.86 K kg mol−1\mathrm{mol^{-1}}, Density of H2O\mathrm{H_2O} = 1.0 g cm−3\mathrm{g\ cm^{-3}}]

Official answer

105

NTA final key.

Chapter
Solutions
Topic
Colligative Properties
Idea tested
Van't Hoff Factor (i)

Same idea in other shifts

Asked 7× in all
  1. 1 Feb 2024, Shift 1 · Q64We have three aqueous solutions of NaCl labelled as 'A', 'B' and 'C' with concentration 0.1 M, 0.01 M and 0.001 M, respectively. The value…MediumSingle correct
  2. 12 Apr 2023, Shift 1 · Q8480 mole percent of MgCl2\mathrm{MgCl_2} is dissociated in aqueous solution. The vapour pressure of 1.0 molal aqueous solution of…MediumNumerical value
  3. 25 Jul 2022, Shift 1 · Q63The depression in freezing point observed for a formic acid solution of concentration 0.5 mL L−10.5\ \mathrm{mL\,L^{-1}} is 0.0405∘0.0405^\circC.…MediumSingle correct
  4. 26 Aug 2021, Shift 1 · Q54Of the following four aqueous solutions, total number of those solutions whose freezing point is lower than that of 0.10 M…EasyNumerical value
  5. 31 Aug 2021, Shift 1 · Q33Which one of the following 0.10 M aqueous solutions will exhibit the largest freezing point depression ?EasySingle correct
  6. 25 Feb 2021, Shift 1 · Q541 molal aqueous solution of an electrolyte A2B3\mathrm{A_2B_3} is 60% ionised. The boiling point of the solution at 1 atm is ________ K.…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.