Question

An element forms a cubic unit cell with edge length 405 pm. Molar mass of this element is 2.7 × 10⁻² kg/mol and its density is given as 2.7 × 10³ kg/m³. How many atoms of these elements are present per unit cell?

Options

• 2

• 1

• 6

• 4

Answer 1

4

Explanation:

d = `("z""M")/("a"^3."N"_"A")`

z = `("d"."a"^3"N"_"A")/("M")`

= `(2.7 xx 10^3  "kg m"^-3 xx (4.05 xx 10^-10  "m") xx 6.022 xx 10^23  "mol"^-1)/(2.7 xx 10^-2  "kg mol"^-1)`

= 4.004

= 4