Question

The pka of hco3 - (or pka2 of h2co3) is 10.33. what is the ph of a solution that has 0.1 m na2co3 and 1.0 m nahco3?

Answer 1

The given solution is a mixture of
`NaHCO_(3)`and
`Na_(2)CO_(3)`. It acts as a buffer as it is a combination of the weak acid
`HCO_(3)^(-)`and it's conjugate base
`CO_(3)^(2-)`.

`[Acid] = [HCO_(3)^(-)]=1.0 M`

`[Base] =[CO_(3)^(2-)]=0.1 M`

pH of the buffer solution can be calculated from Hendersen-Hasselbalch equation as below:

`pH=pK_(a)+log([CO_(3)^(2-)])/([HCO_(3)^(-)])`

`pH=10.33+log(0.1)/(1.0)`

pH = 10.33+(-1)

= 9.33