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## Homework Statement

Calculate the the molar concentration of H

_{3}O+ ions and the pH of the following solutions:

a) 25.0 cm

^{3}of 0.144 M HCl(aq) was added to 25.0 cm

^{3}of 0.125 M NaOH(aq)

b) 25.0 cm

^{3}of 0.15 M HCl(aq) was added to 35.0 cm

^{3}of 0.15 M KOH(aq)

c) 21.2 cm

^{3}of 0.22 M HNO

_{3}(aq) was added to 10.0 cm

^{3}of 0.30 M NaOH(aq)

## Homework Equations

pH = -log[H

_{3}O+] Handerson - Hasselbach eqn.

## The Attempt at a Solution

[/B]

I have only been able to solve part a)

I did that by multiplying the molairty of the strong acid/base by the total volume

then: [H

_{3}O+] = [HCl] - [NaOH] = 9.5 x 10

^{-3}mol

then took the negative log of that number to find the pH = 2.0

which are the correct answers, but when I do that process for part b) and c) which are also strong acid/base combos, the answers are no where near correct.

Any help will be appreciated.