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Saturday, 31 October

JEE Main 2024 · ChemistryNumerical answerNumerical valueHardCalculation

JEE Main 5 April 2024, Shift 2, Chemistry Q84

Question 84 of 90 in this shift, Chemistry question 24 of 30, Section B.

Considering acetic acid dissociates in water, its dissociation constant is 6.25×10−56.25\times10^{-5}. If 5 mL of acetic acid is dissolved in 1 litre water, the solution will freeze at −x×10−2 ∘C-x\times10^{-2}\ ^\circ\mathrm{C}, provided pure water freezes at 0 ∘C0\ ^\circ\mathrm{C}. x=x= ________. (Nearest integer) Given : (Kf)water=1.86 K kg mol−1(\mathrm{K_f})_{\mathrm{water}}=1.86\ \mathrm{K\ kg\ mol^{-1}}. density of acetic acid is 1.2 g mol−11.2\ \mathrm{g\ mol^{-1}}. molar mass of water =18 g mol−1=18\ \mathrm{g\ mol^{-1}}. molar mass of acetic acid =60 g mol−1=60\ \mathrm{g\ mol^{-1}}. density of water =1 g cm−3=1\ \mathrm{g\ cm^{-3}} Acetic acid dissociates as CH3COOH⇌CH3COO⊖+H⊕\mathrm{CH_3COOH \rightleftharpoons CH_3COO^{\ominus} + H^{\oplus}}

Official answer

19

NTA final key.

Chapter
Solutions
Topic
Colligative Properties
Idea tested
Freezing Point Depression

Same idea in other shifts

Asked 16× in all
  1. 4 Apr 2024, Shift 2 · Q842.7 kg of each of water and acetic acid are mixed. The freezing point of the solution will be -x °C. Consider the acetic acid does not…MediumNumerical value
  2. 6 Apr 2024, Shift 2 · Q84When 'xx' ×10−2\times 10^{-2} mL methanol (molar mass =32= 32 g; density =0.792= 0.792 g/cm3^3) is added to 100 mL water (density =1= 1…MediumNumerical valueHas a figure
  3. 30 Jan 2024, Shift 1 · Q63What happens to freezing point of benzene when small quantity of napthalene is added to benzene ?EasySingle correct
  4. 25 Jul 2022, Shift 2 · Q62Two solutions A and B are prepared by dissolving 1 g of non-volatile solutes X and Y, respectively in 1 kg of water. The ratio of…EasySingle correct
  5. 28 Jul 2022, Shift 1 · Q84150 g of acetic acid was contaminated with 10.2 g ascorbic acid (C6H8O6\mathrm{C_6H_8O_6}) to lower down its freezing point by…EasyNumerical value
  6. 30 Jul 2022, Shift 2 · Q5331 g of ethylene glycol is mixed with 500 g of water. The freezing point of the aqueous solution is ________ K. (in nearest integer)…EasyNumerical value
  7. 3 Aug 2021, Shift 2 · Q32The lowest freezing point among the following solutions will be observed in [Atomic weight : C = 12, Mg = 24, Na = 23, Cl = 35.5, O = 16,…EasySingle correct
  8. 26 Aug 2021, Shift 2 · Q5483 g of ethylene glycol dissolved in 625 g of water. The freezing point of the solution is __________ K. (Nearest integer) [Use : Molal…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.