JEE Main 2021 · ChemistryNumerical answerNumerical valueMediumCalculation

JEE Main 25 February 2021, Shift 2, Chemistry Q55

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

If a compound AB dissociates to the extent of 75% in an aqueous solution, the molality of the solution which shows a 2.5 K rise in the boiling point of the solution is ________ molal. (Rounded-off to the nearest integer) [

\mathrm{K_b}=0.52

K kg mol

^{-1}

]

Official answer

NTA final key.

Chapter: Solutions
Topic: Colligative Properties
Idea tested: Degree of Dissociation from Van't Hoff Factor

Same idea in other shifts

Asked 6× in all

7 Apr 2025, Shift 1 · Q72The percentage dissociation of a salt ( $\mathrm{MX_3}$ ) solution at given temperature (van't Hoff factor $i = 2$ ) is ___________ %(Nearest…EasyNumerical value
8 Apr 2024, Shift 1 · Q84A solution containing 10 g of an electrolyte $\mathrm{AB_2}$ in 100 g of water boils at $100.52^\circ$ C. The degree of ionization of the…MediumNumerical value
10 Apr 2023, Shift 1 · Q84If the degree of dissociation of aqueous solution of weak monobasic acid is determined to be 0.3, then the observed freezing point will be…MediumNumerical value
26 Jun 2022, Shift 1 · Q82A 0.5 percent solution of potassium chloride was found to freeze at $-0.24$ °C. The percentage dissociation of potassium chloride is…MediumNumerical value
17 Mar 2021, Shift 2 · Q54A 1 molal $\mathrm{K_4Fe(CN)_6}$ solution has a degree of dissociation of 0.4. Its boiling point is equal to that of another solution…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.