1. Friday, March 14, 2008 Turn in Labs Extra Credit Opportunity Review Homework Section 16.1B – Acid Strength Section 16.1C – Water as an Acid and A Base Homework: Page 589, 13, 14, 16, 17, 18, 20, 22bd, 23bd, 24b, 25b

2. Acid/Base Strength 1.HA(g) + H 2 O(l)  H 3 O + (aq) + A - (aq) When an acid dissolves in water, a proton is transferred from the acid to the water. The new acid (conjugate acid) can react with the conjugate base This reforms the parent acid and water molecule

3. Acid/Base Strength 1.HA(g) + H 2 O(l)  H 3 O + (aq) + A - (aq) 2.H 3 O + (aq) + A - (aq)  HA(g) + H 2 O(l) The reaction can occur in both directions. A forward direction (1) or the reverse direction (2). The question is, which one wins? Which has more attraction for the H + ? Or which gives up H + better?

4. Acid/Base Strength 1.HA(g) + H 2 O(l)  H 3 O + (aq) + A - (aq) 2.H 3 O + (aq) + A - (aq)  HA(g) + H 2 O(l) Strong Acid – the acid is completely ionized or completely dissociates ( all the H + is given away). Weak Acid – does not dissociate to a large extent

5. Acid/Base Strength How can we tell if it is a strong acid? Check to see conductivity! Strong acid will have lots of ions, (H + and Cl - ) and conduct well – weak will not conduct as well

6. Acid/Base Strength Make a larger arrow to show strength A strong acid: the forward direction dominates A strong acid contains a relatively weak conjugate base A weak acid contains a relatively strong conjugate base

7. Acid/Base Strength Diprotic acid – can furnish 2 hydrogen Triprotic acid – H 3 PO 4 H 2 SO 4  H + + HSO 4 - HSO 4 - H + + SO 4 2- Oxyacids – Acids containing oxygen Organic acids – have a carbon atom backbone and a carboxyl group C O OHOH

8. Representation of the behavior of acids of different strengths in aqueous solution.

9. Relationship of acid strength and conjugate base strength for the dissociation reaction.

10. Water as an Acid and a Base pH Scale 16.1C-16.2

11. Ionization and Concentration Amphoteric substance: can behave as an acid or as a base Water is most common Ionization of water transfers a proton from one water molecule to another Forms a hydroxide ion and a hydronium ion

12. Self-ionization of Water H2O(l) + H2O(l) H3O+(aq) + OH-(aq) One water molecule acts as an acid (donates) and the other as a base (accepts) Forward reaction does not occur much Only a tiny amount of the ions are in pure water

13. Self-ionization of Water At 25oC actual concentrations are [H3O+] = [OH-] = 1.0 x 10-7 M Concentrations are equal The product of the two concentrations is [H3O+][OH-] = 1.0 x 10-14 @ 25oC

14. Self-ionization of Water Dilute solutions of water, multiply the concentration of these two ions, always get the same number even if the solution isn’t neutral. What is the number? Kw = [H3O+][OH-] = 1.0 x 10-14 @ 25oC Kw = [H+][OH-] = 1.0 x 10-14 @ 25oC

15. Self-ionization of Water What will happen if the concentration of H+ increases? If it decreases? If [H+] increases, [OH-] decreases Kw – Ion Product Constant [H3O+] = [OH-] = 1.0 x 10-7 M This is a neutral solution

16. Classification of Solutions [H+] = [OH-] neutral [H+] > [OH-] acidic [H+] < [OH-] basic Remember: [H+][OH-] = 1 x 10-14

17. Calculate [H + ] or [OH - ] as required for each of the following solutions at 25 °C, and state whether the solution is neutral, acidic, or basic. a)1.0 x 10 -5 M OH - b)1.0 x 10 -7 M OH - c)10.0 M H + 1.0 x 10 -9 M, basic 1.0 x 10 -7 M, neutral 1.0 x 10 -15 M, acidic Try Practice Problem 16.3 on p.571 –5.0 x 10 -13 M, basic