How will you convert `Na_2CO_3` into `NaHCO_3` and vice versa ?

Explanation

Sodium bicarbonate `(NaHCO_3)` can be obtained by passing carbon dioxide `(CO_2)` through a saturated solution of sodium carbonate. Sodium bicarbonate, being less soluble gets separated from the solution as a white crystalline substance.
`Na_2CO_3 + CO_2 + H_2O to 2NaHCO_3`
When sodium bicarbonate `(NaHCO_3)` is heated, it decomposes to give sodium carbonate `(Na_2CO_3)` and carbon dioxide `(CO_2)`.
`2NaHCO_3 overset(Delta)to Na_2CO_3 + CO_2 uarr + H_2O`