Question

The total number of unit cells present in 80 g of X that crystallises in fcc unit cell is (Atomic mass of X is 40 u)
1) Na\2
2)Na\8
3)Na\4
4)2Na​

Answer 1

Answer:

(3) Na/4

 

​  

​  

 

​

Answer 2

The total number of unit cells present in 80 g of X that crystallises in FCC unit cell is Na/2

Therefore, option (1) is correct.

Explanation:

Given:

80 g of X crystallises in FCC unit cell

To find out:

The total number of unit cells present

Solution:

Number of moles of X = 80/40 = 2

Thus, the number of atoms of X = $2N_A$

Where $N_A$ is Avogadro number

We know that in FCC, in 1 unit cell, there are 4 atoms

Thus,

4 atoms constitute = 1 unit cell

1 atom will constitute = 1/4 unit cell

$2N_A$ atoms will constitute = $2N_A\times \frac{1}{4}$ unit cells

                                           = $\frac{N_A}{2}$  unit cells

Hope this answer is helpful.

Know More:

Q: An element x(atomic weight=80g/mol)having fcc structure,calculate number of unit cells in 8gm of x

Click Here: https://brainly.in/question/9572616