The salt A forms a colourless solution . When `NaHCO_3` was
added to the aqueous solution of `A_1` there was no change observed.
However when the mixed solution was boiled. It becomes milky.
The salt A contains the cation

Options

A. `Mg^(2+)`
B. `Ca^(2+)`
C. either `Ca^(2+)` or `Mg^(2+)`
D. `K^+`

Answer

C

Explanation

With `NaHCO_3` both `Ca^(2+)` and `Mg^(2+)` form `Ca(HCO_3)_2` or `Mg(HCO_3)_2` .These are soluble in water and so no change is observed . On boiling , these decompose to `CaCO_3` or `MgCO_3` respectively which being white insoluble substance cause milkiness