Estimate the approximate `PK_a` of `0.5 M CH_3 COOH.` Degree of dissociation (ionization) is 0.15.
`(log 1.32 = 0.12)`

Options

A. 2
B. 1.5
C. 1.88
D. 0.15

Answer

C

Explanation

`CH_(3)COOH = [H][CH_(3)COO]`
`{:(" "C," "0," "0),(C(1-alpha),alphaxxC,alphaxxC):}`
`K_(a)= (Calphaxxcalpha)/(C(1-alpha))=(Calpha^(2))/(1-alpha)` `(0.5xx0.15xx.015)/(1-0.15)=(0.01125)/(0. 85)=0.0132`
`pK_(a)=-log K_(a)=-log0.0132 rArrpK_(a)= 1.88`