Question

The molar volume of KCl and NaCl are 37.46 ml and 27.94
ml. The ratio of unit cell edges of the two crystals is:
(1) 1.296
(2) 1.116
(3) 1.341
(4) 0.950

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Answer 1

Molar volume =N4/3πr³ where N is Avogadro no ,now Molar volume of KCl is 37.46cm³

so

N 4/3πR³=37.46 cm³ on solving this gives R=2.458 *10-8 cm

and for NaCl by using the same formula it gives R=2.22*10-8 cm

Now the ratio of edge length must be equal to ratio of radii as both belomg to same crystal system so

KCl/NaCl =2.458/2.22= 1.108

hence option B is correct