Calculate the
iii) pH of 0.05 M sodium carbonate solution `pK_(a)` for `HCO_(3)^(-)` is 10.26.

Explanation

Sodium carbonate is a salt of weak acid, `H_2 CO_3` and a strong base, `NaOH`, and hence the solution is alkaline due to hydrolysis.
`Na_2 CO_(3(aq)) to 2Na_((aq))^(+)+CO_(3(aq))^(2-)`
`CO_(3(aq))^(2-)+H_2O(I) hArr HCO_(3)^(-)+OH^(-)`
(iii) `pH =7+(pK_a)/(2)+(logC)/(2) `
`=7+(4.74)/(2)+(log0.1)/(2)=7+2.37-0.5`
`=8.87`