The molecular masses of sulphate and hydroxide of a metal M are 142 and 40 respectively. Calculate atomic mass and valency of the metal.

Explanation

Let the valency of metal be x and atomic meight be m.
`:." Metal sulphate is "M^(+x)SO_4^(-2)rArrM_2(SO_4)_x`
`:. " Metal hydroxide is "M^(+x)OH_4^(-2)rArrM(OH)_x`
`:." Molecular weight of metal sulphate is "`
`2m+96x=142to(1)`
Molecular weight of metal hudroxide is
`m+17x=40`
`rArr2m+34x=80to(2)`
From (1) and (2)
`rArr2m+34x=80`
`((-)(-)(-))/(62x=62)`
`rArrx=1`
`:." From" (1)rArr2m+96(1)=142`
`rArr2m=142-96=46rArrm=23`
`:. " Valency and atomic weight of the metal are 1 and 23 respectively"`.