State as to why a solution of `Na_2CO_3` is alkaline?

Explanation

`Na_2CO_3` is a salt of weak acid `H_2CO_3` and strong base `NaOH` . In aqueous solution, it ionises to form `Na^(+) and CO_3^(2-)` ions.
`Na_2CO_3(aq) hArr 2Na^(+) (aq) + CO_3^(2-) (aq)`
The formed `CO_3^(2-)` ions hydrolyse in aqueous solution to produce acetic acid and `OH^(-)` ion.
`CO_3^(2-) (aq) + 2H_2O(l) hArr H_2CO_3(aq) + 2OH^(-)(aq)`
As `H_2CO_3` is a weak acid, it remains mostly unionised. Consequently, concentration of `OH^(-)` ions increases in the solution thereby making the solution alkaline.