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

Options

A. `2.57 xx 10^(21)`
B. `1.28 xx 10^(21)`
C. `1.71 xx 10^(21)`
D. `5.14 xx 10^(21)`

Answer

A

Explanation

No. of NaCl molecules in a unit cell = 4
Mass of unit cell = `(4 xx 58.5)/(6.022 xx 10^(23))`
No. of unit cells in 1 g = `(1 xx 6.022 xx 10^(23))/(4 xx 58.5)`
`=2.57 x 10^(21)`.