The Math of PH
PH is defined as the NEGATIVE log of the hydrogen ion concentration
PH = -log [H +]
Because H + is always in equilibrium with water and INVERSLY proportional to OH - concentration (as one increases the other decreases).
HOH <---> H + + OH -
We can also have the "POWER of the hydroxide ion" value, or pOH:
POH = -log [ OH -]
Also remember the ion product constant for water:
[H +] x [ OH -] = 1x10 -14 moles/liter 2
With some mathematical manipulation this also means that:
PH + pOH = 14
With all this information, you can solve problems involving pH:
1. What is the pH of a solution with a [H +] of 1 x 10 -8?
2. What is the [H +] of a solution with a pH of 3?
3. What is the pOH of a solution with a pH of 5?
4. What is the [ OH -] of a solution with a pH of 4?
5. If you wanted to change the pH of a solution from 3 to 5, how many times would you dilute it?