Question

890 g of copper is mixed with 100 g of zinc to form brass. The density of copper is 8.9 g/cm³ and the density of zinc is 7.1 g / cm ³ .

a ) What is the volume of copper and zinc used to make the brass ?
b ) Calculate the density of the brass . ​

Answer 1

Density ρ is equal to mass m per unit volume v, or

ρ = m / v

Solve for volume:

v = m / ρ

(a) 890 g of copper, which has a density of 8.9 g/cm³, has a volume of

v = (890 g) / (8.9 g/cm³) = 100 cm³

100 g of zinc, with density 7.1 g/cm³, has a volume of

v = (100 g) / (7.1 g/cm³) ≈ 14.08 cm³

(b) The density of brass is then

ρ = (890 g + 100 g) / (100 cm³ + 14.08 cm³) ≈ 8.68 g/cm³