Question

Rank the conjugate base ions below in order of increasing strength.

hydrogen carbonate ion, HCO3-

acetate ion, Ka = 1.76x10^-5

benzoate ion, Ka = 6.46x10^-5

formate ion, HCOO-

carbonate ion, CO3^2-

How do you determine the strength?

Answer 1

you determine "strneght" on its ability to gain H+ ions, high Ka values, mean very strong low Ka values mean very weak

since pKa is the -log(Ka)

then low pKa values are strong and high pKa are weak

hydrogen carbonate ion, HCO3- pKa = 6.37

acetate ion, Ka = 1.76x10^-5 = pKa = 4.75

benzoate ion, Ka = 6.46x10^-5 = 4.20

formate ion, HCOO- = 3.76

carbonate ion, CO3^2- = 10.32

THEN

the most strong:

formate ionz > benzoate ion > acetate ion > hydrogen carbonate ion > carbnate ion >