1. Acids burn.

2. Bases burn.

3. VI. Strength of Acids and Bases A. Strong acids and bases… 1. completely dissociate (come apart) or ionizes  100% of the molecules become ions 2. are strong electrolytes and dangerous! Ex. acids: HCl, HBr, HI, HNO 3, H 2 SO 4, HClO 4 bases: NaOH and other Group 1 or 2 hydroxides B. Weak acids and bases… 1. dissociate or ionize very little  maybe only 1% of molecules become ions 2. are weak electrolytes Ex: acids: acetic acid, carbonic, and many others bases: ammonia and many others

4. STRONG ACIDS STRONG Bases

6. C. pH Scale 1. In any solution, if you pay attention only to the concentration of hydronium H 3 O + (same as H + !!!) and hydroxide OH - ions… …and use brackets [ ] to mean “the concentration of…” then.. In an acidic solution: [H + ] > [OH - ] In a neutral solution: [H + ] = [OH - ] In a basic solution: [H + ] < [OH - ] Ex. Is the solution shown at right acidic, basic or neutral? H+H+ OH - H+H+ H+H+ H+H+ H+H+ H+H+

8. 2. The pH scale is used to express how acidic or basic a solution is. a/ The pH scale goes from 0 to 14 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 neutral stronger acids more acidic more [H+] or [H 3 O + ] stronger bases more basic more [OH - ] b/ pH = 7 means a neutral solution with [H + ] = [OH - ] Lower pH ( [OH - ] Higher pH (> 7): more basic with [OH - ] > [H + ]

11. Ex. As acid is added to base, what happens to the.. …the pH? …the acidity?…the basicity? …the H 3 O + concentration? …the OH - concentration? Ex. Which pH value is most basic? 11 13 2 74 Ex. Which pH value it most acidic? 11 13 2 74 Ex. Which pH value has the greatest [H 3 O + ]? 11 13 2 74 Ex. Which pH value has the greatest [OH - ]? 11 13 2 74

12. Sometimes it is written right to left:

13. Ex. The list at right gives the pH’s of some common solutions. a/ Write A (acid), B (base) and N (neutral) next to each b/ Put them in order… …from strongest acid to strongest base: …of increasing H + (or H 3 O + ) concentration. …of increasing OH - concentration. bleach: 13 blood: 7.4 coffee: 5 OJ: 3 pure water: 7

15. 3/ pH is logarithmic. This means that… a change …means a change in pH of: in concentration of: 110 1 or 10x 210 2 or 100x 310 3 or 1000x etc Ex. Which has a greater [H + ] or [H 3 O + ]: urine (pH 6) or pure water (pH 7)? How much greater? Which has a greater [OH - ]? How much greater?

17. Ex. Which has a greater [H + ]: soapy water (pH 12) or baking soda (pH 9)? How much greater? Which has a greater [OH - ]? How much greater? Ex. Which has a greater [OH - ]: a can of soda (pH 3) or black coffee (pH 5)? How much greater? Which has a greater [H 3 0 + ]? How much greater? Ex. The pH of a solution changes from 4 to 3. Did the [H + ] decrease or increase? By what factor? Did the [OH - ] dec. or incr.? By what factor?