Calculating pH (and pOH)

[H+] = the hydrogen ion concentration pH pH: “potential of hydrogen” - A way of expressing the hydrogen ion concentration pH = - log [H+] [H+] = the hydrogen ion concentration

Calculating pH Calculate the pH values using the equation pH = - log [H+]. Do you notice a pattern? [H+] pH 1 1 x 10-3 M 2 1 x 10-5 M 3 1 x 10-7 M 4 1 x 10-9 M 5 1 x 10-12 M 3.0 5.0 7.0 9.0 12.0

How do we calculate [H+] if we know the pH? pH = - log [H+] [H+] = the hydrogen ion concentration [H+] = 10-pH

Calculating [H+] Calculate the [H+] values using the equation [H+] = 10-pH. Do you notice a pattern? pH [H+] 1 3.00 2 5.00 3 7.00 4 9.00 5 12.00 1 x 10-3 M 1 x 10-5 M 1 x 10-7 M 1 x 10-9 M 1 x 10-12 M

Calculating pH pH [H+] Acidic Solution pH < 7.0 Neutral Solution Basic Solution pH > 7.0 [H+] > 1 x 10-7 [H+] = 1 x 10-7 [H+] < 1 x 10-7

The pH Scale - As pH increases, [H+] decreases - As pH decreases, [H+] increases

[OH-] = the hydroxide ion concentration pOH pOH: “potential of hydroxide” Just like pH: - pOH is a convenient way of expressing the hydroxide ion concentration pOH = - log [OH-] [OH-] = the hydroxide ion concentration Just like [H+]: [OH-] = 10-pOH pH + pOH = 14