Question

the density of crystalline NaCl is 2.165 g cm-³. Calculate the edge length of the cubic unit cell, if NaCl has face centred cubic lattice structure.​

Answer 1

Solution:

We know that ,

ρ=Na3(MNA)ρ=Na3(MNA)ρ=Na3(MNA)

Where

ρ=density=2.165gcm−3ρ=density=2.165gcm−3ρ=density=2.165gcm−3

M = molar mass = 58.5

NA=Avogadro′snumber=6.023×1023NA=Avogadro′snumber=6.023×1023NA=Avogadro number=6.023×1023

N = number of formula unit per unit cell = 4 (for fcc)

a3=NρMNAa3=Nρ(MNA)a3=Nρ(MNA)

=1.794×10−22=1.794×10−22=1.794×10−22

=5.64×10−8cm

Molar Volume =MolarmassDensity

58.82.165

3 cm

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