1. Acids and Bases

2. An acid is a substance that produces Hydrogen ions, H + (aq) in water (Arrhenius definition). The hydrogen ion (H + ) bonds with a water molecule to make a hydronium ion, H 3 0 + (aq) (H + -> H 2 0 = H 3 O + )

3. Strong acids A strong acid is an acid, which ionizes extremely well. Essentially all of the acid molecules are ionized. (lots of H 3 O + ) Example: HCl, HBr, HNO 3, H 2 SO 4, HClO 4 Example: HCl (aq) + H 2 O(l) -> H 3 0 + (aq) + Cl - (aq) H 2 SO 4 (aq) +2H 2 O(l) -> 2H 3 O + + SO 4 2- (aq) ( Ionization equations show how they react with water to make H 3 O + )

4. Weak acid A weak acid is an acid which ionizes poorly. Only a small percentage of the acid molecules actually ionize. (a few H 3 O + ) Example:HC 2 H 3 O 2 HC 2 H 3 O 2(aq) + H 2 O(l)  H 3 O+(aq) + C 2 H 3 0 2 -

5. Bases A base is a substance that produces hydroxide ions, OH -, in water ( Arrhenius defintion ) A strong base is a base that dissociates 100% in aqueous solution. Example: NaOH(s)  Na + (aq) + OH - (aq) KOH(s) -> K + (aq) + OH - (aq) ( Ionization equations: show how they make ions)

6. Weak base A weak base is a base which ionizes poorly. Only a small percentage of the base molecules actually ionize.(a few OH - Example: NH 3 (aq) + H 2 O(l) -> NH 4 + (aq) + OH - (aq)

7. The pH scale A shorter, more suitable method to express the acidity of a solution. pH stands for potency of hydrogen 0 714 Very acidicneutralvery basic [H 3 O + ]>[OH - ] [H 3 O + ]=[OH - ] [H 3 O + ]<[OH - ]

8. pH = -log[ H 3 O + ] Quantitatively: p (power) represents the negative log H stands for the concentration of hydrogen ions or H 3 0 + ions pH= 2.0 [ H 3 O + ] = 1 x 10 -2 mol/L pH= 3.0 [ H 3 O + ] = 1 x 10 -3 mol/L

9. If the [H 3 O + ] of a solution is 1.0 x 10 -7, determine the pH of the solution pH = -log [ H 3 O + ] = -log(1.0 x 10 -7 ) = -(-7.00) = 7.00

10. Determine the pH for a solution that has [H 3 O + ] = 0.0103 mol/L pH = -log [ H 3 O + ] = -log(0.0103) = 1.99

11. Comparing Acids and Bases Tastes sour Turns phenolpthalein clear Turn bromothymol blue, yellow React with metals and carbonates Turn litmus paper red Tastes bitter Turn phenolphthalein, pink Turn bromothymol blue, blue Turn litmus paper blue