Question

A piece of brass weights 12.9 g in air. When completely immersed in water, it weights 11.3 g. The relative densities of Cu and Zn are 8.9 and 7.1 respectively. Calculate in the alloy.

Answer 1

Loss of weight = (12.9 - 11.3) g = 1.6 g

weight of water displaced = 1.6 g

If m is the mass of Cu, them [m/8.9 + (12.9 - m)/7.1] g = 1.6 g

7.1 m + 12.9 x 8.9 - 8.9 m = 1.6 x 8.9 x 7.1

1.8 m = 114.8 -101.1

m = 7.6 g