`SnO_(2)` form a positively charged colloidal sol in the acidic medium and negatively charged sol in the basic medium. Explain.

Explanation

`SnO_(2)` is ampotericin nature. It reacts with acid, e.g, with HCl to form `SnCl_(4)` in the solution. The common `Sn^(4+)` ions are adsorbed on the surfac of `SnO_(2)` particles thereby giving them a positive charge
`SnO_(2)+4HCl to SnCl_(4)+2H_(2)O`
`SnO_(2)+Sn^(4+)to underset("Positively charged colloidal particles")([SnO_(2)]:Sn^(4+))`
`SnO_(2)` reacts with a base, e.g., NaOH to form sodium stannate `(Na_(2)SnO_(3))` in the solution. The stannate ions are adsorbed on the surface of `SnO_(2)` particles giving them an negative charge.
`SnO_(2)+2NaOH to underset("Sodium stannate")(Na_(2)SnO_(3)+)H_(2)O`
`SnO_(2)+SnO_(3)^(2-)to underset("Negatively charged colloidal particles")([SnO_(2)]:SnO_(3)^(2-))`