Alum in aqueous solution which gives positive test for 

A) K⁺       B) Al³⁺     C) SO₄^2–

The chemical formula for potash alum is $\mathrm{KAl}{\left({\mathrm{SO}}_4\right)}_2$Because of the hydrolysis of Al⁺³ in aqueous media .It is more acidic than nature. When Al is +3 When ions are solvated by water molecules, their high electron density pulls electrons towards them, causing the electron density between O-H in solvating water molecules to decrease. As a result, protons are more likely to be absorbed by water.

Potassium alum is ${\mathrm{K}}_2{\mathrm{SO}}_4.{\mathrm{Al}}_2{\left(\mathrm{SO}\right)}_4.24{\mathrm{H}}_2\mathrm{O}$.

Alum in aqueous solution gives a positive test for A) K+ B) Al³⁺ C) SO₄^2–