Question

An element X with atomic mass 40 gm/mol has a density 4.20 gm/ce, if the edge length is
200 pm, identify the type of unit cell and calculate the radius.
​

Answer 1

Answer:

1.5×10

22

Explanation:

edge length = 400 pm= 400 ×10

−10

cm= 4 ×10

−8

cm

Density =

Avogadro’s number×( edge length)

3

Atomic mass× Number of atoms in 1 unit cell

Density =

6.022×10

23

mol

−1

×( 4 ×10

−8

cm)

3

40gmol

−1

× 4

Density =4.15 g/cm

3

Volume of 4 g of 'X' =

4.15 g/cm

3

4 g

=0.964 cm

3

Volume of one unit cell =( edge length)

3

=( 4 ×10

−8

cm)

3

=6.4×10

−23

cm

3

The number of unit cells in 4g of 'X' =

6.4×10

−23

cm

3

0.964 cm

3

=1.5×10

22