1. More Solutions, A-B Rxns, and LeChatelier’s Principle

2. Water and Water Solutions Conductivity?Why? Distilled H 2 O 0 Ionic, soluble cmpd + H 2 O high Ionic, insoluble cmpd + H 2 O very low Molecular cmpd + H 2 O 0 to high

3. Water and Water Solutions Conductivity?Why? Distilled H 2 O 0 ~No charge carriers (ions) Ionic, soluble cmpd + H 2 O high Ions in solution carry charge (conduct) Ionic, insoluble cmpd + H 2 O very low ~no ions in solution Molecular cmpd + H 2 O 0 to high Does or does not produce ions

4. How Can Molecular Compounds Produce Ions In Water? If solution conducts, the charge carriers (ions) must have resulted from rxn of the molecule with water. e.g., HC 2 H 3 O 2 + H 2 O  C 2 H 3 O 2 - + H 3 O +

5. Investigate This 2.67: What are the properties of aqueous solutions of gases?

6. Results of 2.67a Conductivity Tests distilled water (N 2, O 2, CO 2 (aq)) CO 2 (aq)NH 3 (aq)HCl (aq)C 6 H 12 O 6 (aq) Meter lights if solution conducts.

7. Results of 2.67b pH Tests pH=1 2 3 4 5 6 12 11 10 9 8 7 distilled water (N 2, O 2, CO 2 (aq)) CO 2 (aq)NH 3 (aq)HCl (aq)C 6 H 12 O 6 (aq) plus same indicator indicator added to solutions of known pH

8. CompoundConductivitypH N 2 or O 2 (aq)~0~7 CO 2 (aq)low but >0~5 NH 3 (aq)moderate~12 HCl(aq)very high~2 Summary for Investigate This 2.67 Which cmpds (without water) are ionic? How can you tell? Which mixtures of cmpds + water contain ions? Are there significant amounts of OH - present? H 3 O + ? Write eqns for any rxns that occur between gas + water.

9. Acid-Base Reactions

10. The Arrhenius View Acid - yields H + when added to water HCl (g) + H 2 O (l)   H + (aq) + Cl - (aq) unbalanced Base - yields OH - when added to water NaOH (s) + H 2 O (l)   Na + (aq) + OH - (aq) unbalanced

11. Arrhenius View of Neutralization acid + base a salt + water HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O (l)

12. The Brønsted View More general approach, not limited to water acid = “proton” (H + ) donor base = “proton” (H + ) acceptor Neutralization = “proton” (H + ) transfer

13. Why is HCl a Brønsted Acid? hydronium ion, H 3 O +

14. acidbase Why is Ammonia a Brønsted Base? The double arrow is used to show that this is an equilibrium (reaction is incomplete).

15. acidbase Water Autoionizes in a Brønsted Rxn H-O-H + H-O-H  H 3 O + + OH - Position of this equilibrium lies very far to the left and explains water’s ~0 conductivity. Pure water contains very few ions.

16. pH = -log 10 [H+(aq)] = -log 10 [H 3 O + ] Acidic Neutral Basic

17. Le Chatelier’s Principle A system at equilibrium responds to a disturbance (stress) in a way that minimizes the effect of the disturbance (stress).

18. Equilibrium and LeChatelier’s Principle (Investigate This 2.85) NH 3 + H 2 O  NH 4 + + OH - When water and NH 4 Cl are mixed, this equilibrium is established. (Cl- is a spectator.) Add 2-3 drops of water to NH 4 Cl vial, cap, and mix. Note odor. Odor of NH 3 means equilibrium lies to the left No smell = equilibrium lies to the right Add OH- (disturb the equilibrium). Add 2-3 drops of water to NH 4 Cl-NaOH vial and mix. How does the position of equilibrium compare to NH 4 Cl alone?

19. More Net Ionic Equations

20. Problem: Write the net ionic equation for the reaction of sodium hydroxide and acetic acid in water. whole formula ionic eqn net ionic eqn

21. NaOH(aq) + HC 2 H 3 O 2 (aq) NaC 2 H 3 O 2 (aq) + H 2 O(l) OH - + HC 2 H 3 O 2 C 2 H 3 O 2 - + H 2 O (l) Na + + OH - + HC 2 H 3 O 2 Na + + C 2 H 3 O 2 - + H 2 O strong electrolyte separated ions weak electrolyte mostly molecular strong electrolyte separated ions weak/non- electrolyte molecular whole formula ionic eqn net ionic eqn Problem: Write the net ionic equation for the reaction of sodium hydroxide and acetic acid in water.