Show by a chemical reaction with water that `Na_(2)O` is a basic oxide and `Cl_2O_(7)` is an acidic oxide.

Explanation

`Na _(2)` O reacts with water and forms a strong base
`Na _(2) O + H _(2)O to 2Na OH`
`Cl _(2) O _(7)` reacts with water to form a strong acid.
`Cl _(2) O _(7) + H _(2) O to 2H ClO_(4)`
Their acidic and basic nature can be qualitatively tested with litmus paper. As we know acids turn blue litmus paper red while bases turn red litmus paper blue.