JEE Main 2021ChemistryIonic EquilibriumMediumNumerical

JEE Main 2021 — Ionic Equilibrium Question with Solution

JEE Main 2021 (17 Mar Shift 1)

Question

0.01 moles of a weak acid HA Ka=2.0×10-6 is dissolved in 1.0 L of 0.1M HCl solution. The degree of dissociation of HA is __________ ×10-5 (Round off to the Nearest Integer). [Neglect volume change on adding HA and assume degree of dissociation <<1]

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Show full solutionCorrect answer: 2
Correct answer
2

Step-by-step explanation

HA        ⇌            H+               +   A-Initial conc.          0.1M0M           Equ. conc. (0.01-x)             (0.1+x)xM≈0.01M               ≈0.1M

Now, Ka=H+A-[HA]⇒2×10-6=0.1×x0.01

∴x=2×10-7

Now, α=x0.01=2×10-70.01=2×10-5

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About this question

This is a previous-year question from JEE Main 2021, covering the Ionic Equilibrium chapter of Chemistry. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.