Potassium crystallizes in a body centered cubic lattice. What is the approximate number of unit cells in 4.0g of potassium? Atomic mass of potassium = 39.

Explanation

There will be eight atoms at corners of the cube and one atom at the body centre.
`therefore` Number of atoms per unit cell `=8xx(1)/(8)+1xx1=2`
Number of atoms in 4.0g of potassium `=(4)/(39)xx6.023xx10^(23)`
`therefore` Number of unit cells in 4.0g of potassium `=(4)/(39)xx(6.023xx10^(23))/(2)=3.09xx10^(22)`