equilibrium equations

Question 1

Strong acid/base [HA] > 10^-6

Answer 1

• acid dominates pH= -log [HA]

Question 2

Strong acid

10^-6 > [HA] > 10^-8

Answer 2

• neither acid or water dominates
• must use systematic method

1. write species, CB, MB and Kw = [OH-] [H+]
2. 3 equations 3 unknowns
3. isolate for [H+] bc want pH
4. sub MB into CB for ion (K+, Cl- …)
5. sub into Kw
6. expand to get quadratic
7. solve

Question 3

Strong acid/base

10^-8 > [HA]

Answer 3

• water dominates

pH=7