2. PROPERTIES OF: ACIDS Taste sour Blue litmus turns red Reacts with metals to make H 2 gas. Contains a H at the start of the formula(HCl, H 2 SO 4 ) BASES Taste bitter Feel slippery Turn red litmus blue Turns phenolphthalein pink Contains OH at the end of the formula (NaOH, KOH)

3. Arrhenius’ Theory of Acids & Bases (1885) Arrhenius said that an acid is a substance which liberates hydrogen ions. HCl (l) H + (aq) + Cl - (aq)

4. Arrhenius said that a base is a substance which liberates hydroxide ions. NaOH (s) Na + (aq) + OH - (aq)

5. pH Scale Soren Sorensen (1868 - 1939)

6. pH Scale Acid Base 0 7 14 Zumdahl, Zumdahl, DeCoste, World of Chemistry  2002, page 515 [H + ] pH 10 -14 14 10 -13 13 10 -12 12 10 -11 11 10 -10 10 10 -9 9 10 -8 8 10 -7 7 10 -6 6 10 -5 5 10 -4 4 10 -3 3 10 -2 2 10 -1 1 10 0 0 1 M NaOH Ammonia (household cleaner) Blood Pure wate Milk Vinegar Lemon juice Stomach acid 1 M HCl Acidic Neutral Basic

7. DID YOU KNOW! Some plants will have different colour blooms depending on what the pH of their soil is. Example the hydrangea plant. Hydrangeas blooms are blue when they are in acidic soil and pink when they are in basic soil.

9. Acid Solutions [H + ] > [ OH - ] Base Solutions [OH - ] > [H + ] Neutral Solutions [H + ] = [ OH - ]

10. How to find the pH? [H + ] is critical in many chemical reactions. A quick method of denoting [H + ] is via pH. pH= - log [H + ] Ex 1: [H + ] = 1 x 10 -6 mol/L pH = - log [1 x 10 -6 ] = 6

11. Ex 2: If the pH =3.7, what is the [H + ]? [H + ] = 10 -pH = 10 -3.7 = 2 x 10 -4 mol/l

12. pH Calculations pH pOH [H + ] [OH - ] pH + pOH = 14 pH = -log[H + ] [H + ] = 10 -pH pOH = -log[OH - ] [OH - ] = 10 -pOH [H + ] [OH - ] = 1 x10 -14

13. The Bronsted-Lowry concept Acids and bases are identified based on whether they donate or accept H +. “Conjugate” acids and bases are found on the products side of the equation. H 3 O + is called the hydronium ion + ClH H H O + H H HO + acidbase conjugate acidconjugate base conjugate acid-base pairs

14. Practice problems Identify the acid, base, conjugate acid, conjugate base, and conjugate acid-base pairs: acidbase conjugate acidconjugate base HC 2 H 3 O 2 (aq) + H 2 O (l) C 2 H 3 O 2 – (aq) + H 3 O + (aq) conjugate acid-base pairs acidbase conjugate acidconjugate base OH – (aq) + HCO 3 – (aq) CO 3 2– (aq) + H 2 O (l) conjugate acid-base pairs

15. acidbase conjugate acidconjugate base HF (aq) + SO 3 2– (aq) F – (aq) + HSO 3 – (aq) conjugate acid-base pairs acidbase conjugate acidconjugate base CO 3 2– (aq) + HC 2 H 3 O 2 (aq) C 2 H 3 O 2 – (aq) + HCO 3 – (aq) conjugate acid-base pairs acidbase conjugate acidconjugate base H 3 PO 4 (aq) + OCl – (aq) H 2 PO 4 – (aq) + HOCl (aq) conjugate acid-base pairs More Practice: (a) (b) (c)

16. acidbase conjugate baseconjugate acid HCO 3 – (aq) + S 2– (aq)  HS – (aq) + CO 3 2– (aq) conjugate acid-base pairs baseacid conjugate acidconjugate base H 2 CO 3 (aq) + OH – (aq)  HCO 3 – (aq) + H 2 O (l) conjugate acid-base pairs acidbase conjugate acidconjugate base H 3 O + (aq) + HSO 3 – (aq)  H 2 O (l) + H 2 SO 3 (aq) conjugate acid-base pairs d) e) f) baseacid conjugate baseconjugate acid OH – (aq) + HSO 3 – (aq)  H 2 O (l) + SO 3 2– (aq) conjugate acid-base pairs g)