What is the `pH` of `0.01 M` glycine solution? For glycine, `K_(a_(1))=4.5xx10^(-3)` and `K_(a_(2))=1.7xx10^(-10)` at `298 K`

Options

A. `3.0`
B. ` 10.0 `
C. `7.06 `
D. `8.2 `

Answer

C

Explanation

Glycine `H_(3)N'CH_(2)COO^(-)` is more acidic than basic. Instead of `K_(b)` value, the second given `K_(a)` value ois corresponding to the `K_(b)` value `(therefore K_a xx K_b) =10^(-14))`. Hence, overall ionization constant.
`K=K_(a_(1))=K_(a_(2))=4.5xx10^(-3)xx1.7xx10^(-10)`
`=7.65xx10^(-13)`
`H^(+)=sqrt(KC)=sqrt(7.65xx10^(-13)xx0.01)`
`H^(+)=sqrt(KC)=sqrt(7.65xx10^(-13)xx0.01`
`=sqrt(0.765xx10^(-14)))=0.87xx10^(-7)M`
`pH=-log(0.87xx10^(-7))=7.06`