JEE Main 2019ChemistrySolid StateEasyMCQ

JEE Main 2019 — Solid State Question with Solution

JEE Main 2019 (08 Apr Shift 2)

Question

Consider the bcc unit cells of the solids 1 and 2 with the position of atoms as shown below. The radius of atom B  is twice that of atom A. The unit cell edge length is 50 % more in solid 2 than in 1 . What is the approximate packing efficiency in solid 2 ?

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Show full solutionCorrect option: A
Correct answer
A90 %

Step-by-step explanation

If radius of A is r radius of B will be 2r . Atoms in the body diagonal touch.

Therefore:
r+2r+2r+r=3 a

6 r=3 a or a=6r3

Packing Efficiency
=1×43πr3+1×43π(2r)3a3=43πr3×9(6r/3)3
=4×9×π×r3×333×216×r3=90.5 %

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About this question

This is a previous-year question from JEE Main 2019, covering the Solid State 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.