Q. A metallic element exists in simple cubic structure. Each edge length of the unit cell is 3$A^0$.The density of metal is 10 gm $c{m}^{-3}$. How many unit cells will be there in 16.2 gm of the metal?

(A) 16 x ${10}^{22}$ 
(B) 16 x ${10}^{31}$
(C) 28 
(D) 42 

Dear student,
Kindly mention which question needs to be asked. For better answering please upload each question separately.
Solving Question number 25 for you.
For a BCC system, number of atoms in a unit cell = 2
Density = (M x Z)/(N_A x a³)
Putting the respective values in the expression we get density = 1.002 x 10³ kg/m³

Hope it helps
Regards