Lithium metal crystal has body-centred cubic structure. Its density is `0.53 g cm^(-3)` and its molecular mass is `6.94 g mol^(-1)`. Calculate the volume of a unit cell of lithium metal. `[NA = 6.023 xx 10^(23) mol^(-1)]`

Explanation

For bcc structure `z=2`.
Apply the relation :
`d=(zxxM)/(a^(3)xxN_(A)) or a^(3)=(zxxM)/(d xxN_(A))`
Substituting the values, we get
`a^(3)=(2xx6.94)/(0.53xx6.023xx10^(23))`
or `" Volume of unit cell "(a^(3))=(13.88)/(3.192)xx10^(-23)=4.348xx10^(-23)cm^(3)`.