Which of the following acids is the weakest? the acid is followed by its ka value. a) hc2h302, 1.8 * 10-5 b) hio, 23 x 10-11 oc) hbro, 23 10-9 od) hcio, 2.9 ~ 10-8 o ecohco2h 63 x 10-5

the weakest acid is B) HIO

Explanation:

pKa = - log Ka

the higher the value of pKa, the lower the dissociation, therefore, an acid will be stronger the lower its pKa.

a) HC2H3O2; Ka = 1.8 E-5

⇒ pKa1 = - Log (1.8 E-5) = 4.745

b) HIO;  Ka = 23 E-11

⇒ pKa2 = - Log ( 23 E-11 ) = 9.638

c) HBrO;  Ka = 23 E-9

⇒ pKa3 = - Log ( 23 E-9 ) = 7.638

d) HClO;  Ka = 2.9 E-8

⇒ pKa4 = - Log ( 2.9 E-8 ) = 7.537

e) HCO2H; Ka = 63 E-5

⇒ pKa5 = - Log ( 63 E-5 ) = 3.200

from the values pKa, we places the acids from the weakest to the least weak:

1) pKa2; HIO (weakest)

2) pKa3

3) pKa4

4) pKa1

5) pKa5