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 :
A
1.296
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B
1.116
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C
1.341
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D
0.950
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Solution
The correct option is B 1.116 Molar volume =NA×43πr3 where NA is Avogadro number,
Now Molar volume of KCl is 37.46cm3 So NA×43πR3=37.46cm3 6.022×1023×43πR3=37.46cm3
On solving this gives R=2.458×10−8cm
And for NaCl by using the same formula it gives R=2.22×10−8cm
Now the ratio of edge length must be equal to ratio of radii as both belong to same crystal system so KClNaCl=2.4582.22=1.108