Question

How many unit cells are present in a cube-shaped crystal of NaCl of mass 1.00g?
A. `2.57xx10^21`
B. `5.14xx10^21`
C. `1.28xx10^21`
D. `1.71xx10^21`

Answer 1

Correct Answer - A
Mass of one unit cell `=Vxxd=a^3xxd,`
Where, `d=(Z.M)/(a^3.N_A)`
of 1 unit cell `=(ZM)/(N_A) = (4xx58.5)/(6.02xx10^23) = 38.87xx10^(-23)g`
Number of unit cell in 1g `=(1)/(38.87xx10^(-23)=2.57xx10^21`