1. HAVE A GREAT BREAK! REMINDER: NO LAB Announcements

2. Types of Chemical Reactions Chapter 4 Goals: To be able to predict chemical reactivity. To know how to synthesize specific compounds.

3. Types of Reactions Acid-Base Oxidation-Reduction Precipitation Gas Forming Organic:  Substitution  Addition  Elimination

4. Reactions in Aqueous Solution Aqueous- solvent is water Reactions we’ll discuss today/next week are in aqueous solution, unless otherwise noted  Acid-Base  Redox  Precipitation

5. Electrolytes Strong: All of the solute comes apart to yield ions in solution  Dissolution of KMnO 4 Dissolution of KMnO 4 Weak: Some of the solute comes apart to yield ions Nonelectrolytes: No ions formed  Let’s compare Let’s compare

6. Electrolytes in the Human Body Most important: Na +, Cl -, K +, Ca 2+, Mg 2+,HCO 3 -, and PO 4 3-, SO 4 2- Elevated K +  cardiac arrythmia Decreased extracellular K +  paralysis Excess extracellular Na +  fluid retention Decreased plasma Ca 2+ and Mg 2+  muscle spasms

7. Acids and Bases Theories- there’s lots of them Ones we’ll use in this course  Lewis (later)  Brønsted-Lowry (now)  An acid is a substance that donates a proton (H + ) to a base  The hydronium ion

8. Brønsted-Lowry Definitions Acid= donates a proton (H + ) to a base Base= accepts a proton (H + ) from an acid Acid base reactions are reversible (almost always)

9. Brønsted-Lowry Definitions Acid= donates a proton (H + ) to a base Base= accepts a proton (H + ) from an acid Acid base reactions are reversible (almost always)

10. Important Acids and Bases

11. Strong Acids 100% of acid molecules produce ions in water  Dissociation vs. ionization

12. Weak Acids Only a few acid molecules produce ions (≤5%) Strong vs. Weak acid ionization

13. Polyprotic Acids Polyprotic acids can donate more than one H +  Sulfuric acid  Citric acid (C 6 H 8 O 7 ) : Not all H’s are acidic H 2 SO 4  H + + HSO 4 - HSO 4 -  H + + SO 4 2-

14. Bases Strong bases are hydroxide salts For now, the only important weak base is NH 3.

15. If H 3 PO 4 reacts as an acid, which of the following can it not make? 1. H 4 PO 4 + 2. H 2 PO 4 - 3. HPO 4 2- 4. PO 4 3-

16. If C 2 O 4 2- (oxalate ion) reacts in an acid-base reaction, which of the following can it not make? 1. H 2 C 2 O 4 2. HC 2 O 4 - 3. 2 CO 2 20

17. Acid Base Reactions

18. Strong Acid + Strong Base HCl(aq) + NaOH(aq)  NaCl(aq) + H 2 O(l) acid base “salt” water What do we get if we mix: HBr + LiOH 

19. Acid Base Reactions Diprotic acids or bases H 2 SO 4 (aq) + NaOH(aq)  H 2 SO 4 (aq) + Ba(OH) 2 (aq)  HCl(aq) + Ba(OH) 2 (aq) 

21. Acid-Base Reactions Diprotic Acids or Bases H 2 SO 4 (aq) + NaOH(aq)  H 2 SO 4 (aq) + Ba(OH) 2 (aq)  HCl(aq) + Ba(OH) 2 (aq) 

22. Acid-Base Reactions Strong Acid + Weak Base HCl(aq) + NH 3 (aq)  NH 4 Cl(aq)

23. Acid-Base Reactions Weak Acid + Strong Base HCN(aq) + NaOH(aq)  NaCN(aq) + H 2 O(l) acid base “salt” water

24. Net Ionic Equations HCl(aq) + NaOH(aq)  NaCl(aq) + H 2 O(l) What really happens: H + (aq) + OH - (aq)  H 2 O(l) Sodium ion and chloride ion are “spectator ions”

25. Reactions involving weak bases HCl(aq) + NH 3 (aq)  NH 4 + (aq) + Cl - (aq) Net-Ionic Equation: NH 3 (aq) + H + (aq)  NH 4 + (aq)

26. CH 3 CO 2 H(aq) + NaOH(aq)  1. CH 3 CO 2 H 2 + (aq) + NaO(aq) 2. CH 3 CO 2 - (aq) + H 2 O(l) + Na + (aq) 3. CH 4 (g) + CO 2 (g) + H 2 O(l)

27. HCN(aq) + NH 3 (aq)  1. NH 4 + (aq) + CN - (aq) 2. H 2 CN + (aq) + NH 2 - (aq) 3. C 2 N 2 (s) + 3 H 2 (g)

28. Solution Concentration: Molarity Molarity = moles solute per liter of solution 0.30 mol NH 3 dissolved in 0.500 L Concentration = Written like: [NH 3 ] = 0.60 M

29. pH Scale In pure water, a few molecules ionize to form H 3 O + and OH – H 2 O + H 2 O  OH – + H 3 O + In acidic and basic solutions, these concentrations are not equal acidic: [H 3 O + ] > [OH – ] basic: [OH – ] > [H 3 O + ] neutral: [H 3 O + ] = [OH – ]

30. pH Scale Measure how much H 3 O + is in a solution using pH pH < 7.0 = acidic pH > 7.0 = basic pH = 7.0 = neutral Measure of H 3 O + and OH – concentration (moles per liter) in a solution As acidity increases, pH decreases

31. pH Scale The pH scale is logarithmic: 10010 2 log(10 2 ) = 2 1010 1 log(10 1 ) = 1 110 0 log(10 0 ) = 0 0.110 –1 log(10 –1 ) = –1 0.0110 –2 log(10 –2 ) = –2 The pH scale is logarithmic: 10010 2 log(10 2 ) = 2 1010 1 log(10 1 ) = 1 110 0 log(10 0 ) = 0 0.110 –1 log(10 –1 ) = –1 0.0110 –2 log(10 –2 ) = –2 pH= –log [H 3 O + ] pH= –log [H 3 O + ] pH if [H 3 O + ] = 10 –5 ? 10 –9 ? Acidic or basic? pH if [H 3 O + ] = 10 –5 ? 10 –9 ? Acidic or basic? pH if [H 3 O + ] = 0.000057 M? pH if [H 3 O + ] = 0.000057 M?

32. [H 3 O + ] from pH Finding [H 3 O + ] from pH [H 3 O + ] = 10 -pH What is [H 3 O + ] if pH = 8.9?

33. pH: Quantitative Measure of Acidity Acidity is related to concentration of H + (or H 3 O + ) pH = -log[H 3 O + ]