Question

a coating of Cobalt that is 0.005 CM thick is deposited on a plate that is 0.5 metre square in total area how many atoms of Cobalt not deposited on the plate if density of Cobalt is equal to 8.9 gram per centimetre cube and atomic mass of Cobalt is equal to 59 atomic mass unit​

Answer 1

volume of cobalt coating on the plate , V = area × thickness

= 0.5 m² × 0.005 cm

= 0.5 × (100)² cm² × 5 × 10^-3 cm

= 25 cm³

now, mass of cobalt used in coating = density of cobalt × volume of cobalt coating on the plate

= 8.9 g/cm³ × 25cm³

= 222.5 g

molecular weight of cobalt = 59g/mol

so, number of mole of cobalt deposited on the plate = 222.5/59 = 3.77

so, number of cobalt atoms deposited on the plate = 3.77 × 6.023 × 10²³

= 22.7 × 10²³

= 2.27 × 10²⁴

hence, answer is 2.27 × 10²⁴

Answer 2

Answer:

2.27 × 10²⁴ atoms

Explanation:

Volume of cobalt coating on the plate , V = area × thickness

= 0.5 m² × 0.005 cm

= 0.5 × (100)² cm² × 5 × 10^-3 cm

= 25 cm³

now, mass of cobalt used in coating = density of cobalt × volume of cobalt coating on the plate

= 8.9 g/cm³ × 25cm³

= 222.5 g

molecular weight of cobalt = 59g/mol

so, number of mole of cobalt deposited on the plate = 222.5/59 = 3.77

so, number of cobalt atoms deposited on the plate = 3.77 × 6.023 × 10²³

= 22.7 × 10²³

= 2.27 × 10²⁴

hence, answer is 2.27 × 10²⁴ atoms