A is a binary compound of a univalent metal. When 1.422 g of A reacts completely with 0.321 g of sulphur in an evacuated and sealed tube, 1.743 g of white crystalline solid B produced, which produces a hydrated double salt C with `Al_(2)(SO_(4))_(3)`. Identfy A, B and C.

Explanation

Alum has `Al_(2)(SO_(4))_(3)` and `M_(2)SO_(4)`
`0.321g` sulphur`implies1.743` g of metal sulphate
`32.1g` sulphate`implies(1.743)/(0.321)xx32.1=174.3g` metal sulphate
For `M_(2)SO_(4)`
`M+32+64=174.3`
or `M=39`
Which is the atomic mass of K.
B is `K_(2)SO_(4)`
C is `K_(2)SO_(4).Al_(2)(SO_(4))_(3).24H_(2)O`
The formula `K_(2)SO_(4)` shows that S has reacted with 2 " mol of "`KO_(2)`
`2KO_(2)+StoK_(2)SO_(4)`
`0.321g` sulphur`implies1.422g` g of metal oxide
`32.1` sulphur `implies(1.422)/(0.321)xx32.1=142.2` metal oxide
For `2KO_(2)`
`Mass`=2(39+32)=142`
C is `KO_(2)`.