DO NOW... HINT...if log (x) = y, then x = 10y 1) If log (109) = 9, what is log (100) equal to? 2) If log (Q) = 3, what is Q equal to? HINT...if log (x) = y, then x = 10y

Richter Scale - Earthquakes 6 5 7 Area Radius Richter Scale Diameter pH [H+] 1000000 564 7 1128 mm 1 0.1 M 100000 178.4 6 356.8 2 0.01 M 10000 56.4 5 112.8 3 0.001 M 1000 17.8 4 35.6 4 0.0001 M 100 5.64 3 11.28 5 0.00001 M 10 1.784 2 1.128 6 0.000001 M 1 0.564 1 ------ 7 0.0000001 M . 4 3 2 1

radius = 112.8 cm radius = 35.7 cm radius = 11.3 cm radius = 3.6 cm pH = 2 pH = 3 pH = 1 Area Radius Richter Scale Diameter pH 1000000 564 7 1128 mm 1 100000 178.4 6 356.8 2 10000 56.4 5 112.8 3 1000 17.8 4 35.6 4 100 5.64 3 11.28 5 10 1.784 2 1.128 6 1 0.564 1 ------ 7 . pH = 4 5 6

The pH scale is a way of expressing the strength of acids and bases The pH scale is a way of expressing the strength of acids and bases. Instead of using very small numbers, we just use the NEGATIVE power of 10 on the Molarity of the H+ (or OH-) ion. Under 7 = acid 7 = neutral Over 7 = base

pH of Common Substances

pH of Common Substance More basic More acidic 14 1 x 10-14 1 x 10-0 0 pH [H1+] [OH1-] pOH 14 1 x 10-14 1 x 10-0 0 13 1 x 10-13 1 x 10-1 1 12 1 x 10-12 1 x 10-2 2 11 1 x 10-11 1 x 10-3 3 10 1 x 10-10 1 x 10-4 4 9 1 x 10-9 1 x 10-5 5 8 1 x 10-8 1 x 10-6 6 6 1 x 10-6 1 x 10-8 8 5 1 x 10-5 1 x 10-9 9 4 1 x 10-4 1 x 10-10 10 3 1 x 10-3 1 x 10-11 11 2 1 x 10-2 1 x 10-12 12 1 1 x 10-1 1 x 10-13 13 0 1 x 100 1 x 10-14 14 NaOH, 0.1 M Household bleach Household ammonia Lime water Milk of magnesia Borax Baking soda Egg white, seawater Human blood, tears Milk Saliva Rain Black coffee Banana Tomatoes Wine Cola, vinegar Lemon juice Gastric juice More basic 7 1 x 10-7 1 x 10-7 7 More acidic

(Remember that the [ ] mean Molarity) Calculating the pH pH = - log [H+] (Remember that the [ ] mean Molarity) Example: If [H+] = 1 X 10-10 pH = - log 1 X 10-10 pH = - (- 10) pH = 10 Example: If [H+] = 1.8 X 10-5 pH = - log 1.8 X 10-5 pH = - (- 4.74) pH = 4.74

Try These! Find the pH of these: A 0.15 M solution of Hydrochloric acid 2) A 3.00 X 10-7 M solution of Nitric acid

pH calculations – Solving for H3O+ If the pH of Coke is 3.12, [H3O+] = ??? Because pH = - log [H3O+] then - pH = log [H3O+] Take antilog (10x) of both sides and get 10-pH = [H3O+] [H+] = 10-3.12 = 7.6 x 10-4 M *** to find antilog on your calculator, look for “Shift” or “2nd function” and then the log button

pH calculations Solving for H3O+ A solution has a pH of 8.5. What is the Molarity of hydrogen ions in the solution?

pH Calculations pH = -log[H3O+] 10-pH = [H3O+] pOH = -log[OH-] pH + pOH = 14 [H3O+] [OH-] = 1 x10-14 The pH scale is a concise way of describing the H3O+ concentration and the acidity or basicity of a solution • pH and H+ concentration are related as follows: pH = –log10[H+] or [H+] = 10–pH • pH of a neutral solution ([H3O+] = 1.00 x 10–7 M) is 7.00 • pH of an acidic solution is < 7, corresponding to [H3O+] > 1.00 x 10–7 • pH of a basic solution is > 7, corresponding to [H3O+] < 1.00 x 10–7 • The pH scale is logarithmic, so a pH difference of 1 between two solutions corresponds to a difference of a factor of 10 in their hydronium ion concentrations There is an analogous pOH scale to describe the hydroxide ion concentration of a solution; pOH and [OH–] are related as follows: pH = –log10[OH–] or [OH–] = 10–pOH • A neutral solution has [OH–] = 1.00 x 10–7, so the pOH of a neutral solution is 7.00 • The sum of the pH and the pOH for a neutral solution at 25ºC is 7.00 + 7.00 = 14.00 pKw = –log Kw = –log([H3O+] [OH–]) = (–log[H3O+]) + (–log[OH–]) = pH + pOH • At any temperature, pH + pOH = pKw, and at 25ºC, where Kw = 1.01 x 10–14, pH + pOH = 14.00; pH of any neutral solution is just half the value of pKw at that temperature pOH pOH = -log[OH-] [OH-] 10-pOH = [OH-]

Acid – Base Concentrations pH = 3 pH = 11 10-1 H3O+ OH- pH = 7 10-7 concentration (moles/L)‏ H3O+ OH- OH- H3O+ 10-14 [H3O+] > [OH-] [H3O+] = [OH-] [H3O+] < [OH-] acidic solution neutral solution basic solution Timberlake, Chemistry 7th Edition, page 332

PRACTICE pH & pOH PROBLEMS [ H3O+] (M) pOH [ OH– ] ACID or BASE? 3.78 ? 3.89 x 10–4 5.19 1.00 x 10-7 1.66x10-4 10.22 6.03 x 10-11 ACID 3.41 10.59 2.57 x 10-11 ACID 1.55 x 10-9 6.46 x 10-6 BASE 8.81 7.00 1.00 x 10-7 7.00 NEUTRAL