A metal M readily forms its sulphate `MSO_(4)` which is water soluble. It forms its oxide MO which becomes inert on heating. It forms its insoluble hydroxide `M(OH)_(2)` which is soluble in NaOH solution. What would be M?

Options

A. `Be`
B. `Mg`
C. `Ca`
D. `Sr`

Answer

A

Explanation

Given, `M` reacts to give `MSO_(4)`, which is water soluble. `M` reacts to give `M (OH)_(2)`, which is water insoluble. `M` reacts to give `MO`, which becomes inert on heating. `M(OH)_(2)` is soluble in `NaOH`, this indicates that `M` is `Be`, since only `Be`, due to its small size and high ionisation enthalpy, is amphoteric and gives `M(OH)_(2)` which dissolves in `NaOH`.
`Be(OH)_(2)+2NaOHrarrNa_(2)BeO_(2)+2H_(2)O`
other facts given are true for `Be` and not for others.