Question

What is the mass of unit cell of gold if it crystallises in fee structure?
(At mass of gold= 197 g mol^-1)

Options

• 130.85 × 10^-23 g

• 98.14 × 10^-23 g

• 32.71 × 10^-23 g

• 65.42 × 10^-23 g

Answer 1

130.85 × 10^-23 g

Explanation:

Mass of 1 mole of Gold atoms = 197 g/mol (6.022 × 10²³ atoms)

Mass of 1 atom of gold = `197/(6.022 xx 10^23)`

FCC cell has 4 atoms.

So mass of gold in unit cell = `197/(6.022 xx 10^23) xx 4 = 1.3085 xx 10^-21 "g"`

= 130.85 × 10^-23 g