Question

How many unit cells are present in a cube-shaped ideal crystal of NaCl of mass 1.00 g ?
[Atomic mass : Na=23 , Cl=35.5]
A. `5.14xx10^21`
B. `1.28xx10^21`
C. `1.71xx10^21`
D. `2.57xx10^21`

Answer 1

Correct Answer - D
One unit cell has 4 NaCl units , i.e., has mass `=(4xx58.5)/(6.02xx10^23)`g
`therefore` No. of unit cell in 1 g =`(6.02xx10^23)/(4xx58.5)`
`=2.57xx10^21`