Brass is an ally of Cu and Zn. A sample of brass weighing 5.793 g when treated with excess of dil `H_2SO_4` gives 324 " mL of " dry `H_2` at `20^@C` and 750 mm pressure. What is the percentage of Cu by weight in the alloy.

Explanation

Only Zn reacts with dil `H_2SO_4` to give `H_2` gas
`Zn+H_2SO_4toZnSO_4+H_2uarr`
Weight of `H_2` evolved`=(MPV)/(RT)=(2xx750xx0.324L)/(760xx0.082xx293)`
`=0.02662g`
The amount of Zn in the alloy `=(0.02662xx65.4)/(2)`
`=.871g`
The amount of Cu in the alloy `=5.793-0.871-=4.922g`
`%` of `Cu=(4.922)/(5.793)xx100=85%`