Question

Arrange the following 0.10 M aq. sol. in order of increasing pH.
KOBr, HOBr, LiOH, HBrO4, NaBrO4
(Ka for HOBr = 2.5 x 10^-9, Ka for HBrO4 = 3.2 x 10^8)

I was wondering how to solve this. I know LiOH is a strong base so its pH is the highest. And I know that I can use ICE to individually solve for the 'x' then use that to get pH. But that's only the 2 whose Ka was given. Is there a way to solve this quickly?

Answer 1

KOBr, HOBr, LiOH, HBrO4, NaBrO4
Here's a crack at it with no calculations.

HBrO4 is the strong acid so pH = 1. This will be the lowest pH.

NaBrO4 is the salt of a strong base and strong acid; therefore, pH = 7

LiOH is a strong base so this is the highest @ pH = 13

HOBr is a weak acid so it should be between 1 and 7. Guess @ 4-6
KOBr will hydrolyze in H2O and will be basic so it will be between 7 and 13. Guess @ 10-12.
Check it out.