How many unit cell are present in a cubic-shaped ideal crystal of `NaCl` of mass `1.0 g`?

Options

A. `1.28xx10^(21)` unit cells
B. `1.71xx10^(21)` unit cells
C. `2.57xx10^(21)` unit cells
D. `5.14xx10^(21)`unit cells

Answer

C

Explanation

`n=4` for `f.c.c.,`
Also no. of atoms in `1 g NaCl=(6.023xx10^(23))/(58.5)`
No. of unit cell present in `1g NaCl`
`=(6.023xx10^(23))/(58.5xx4)`
`=2.57xx10^(21)` unit cell