1. Chapter 15 &

2. Properties of acids n Taste Sour (kids, don’t try this at home). n Conduct electricity. n Some are strong, some are weak electrolytes. n React with metals to form hydrogen gas. n Change indicators (litmus red). n React with hydroxides to form water and a salt.

3. Properties of bases n React with acids to form water and a salt. n Taste bitter. n Feel slippery (Don’t try this either). n Can be strong or weak electrolytes. n Change indicators (litmus blue).

4. n electrolytes  electrolytes n turn litmus red n sour taste n react with metals to form H 2 gas n slippery feel n turn litmus blue n bitter taste n vinegar, milk, soda, apples, citrus fruits n ammonia, lye, antacid, baking soda Properties

5. Water n Water ionizes- falls apart into ions. H 2 O  H + + OH - H 2 O  H + + OH - n Called the self ionization of water. n Only a small amount. n [H + ] = [OH - ] = 1 x 10 -7 M n A neutral solution. n In water Kw = [H + ] x [OH - ] = 1 x 10 -14 n Kw is called the ion product constant.

6. Ionization of Water H 2 O + H 2 O H 3 O + + OH - K w = [H 3 O + ][OH - ] = 1.0  10 -14

7. Ionization of Water n Find the hydroxide ion concentration of 3.0  10 -2 M HCl. [H 3 O + ][OH - ] = 1.0  10 -14 [3.0  10 -2 ][OH - ] = 1.0  10 -14 [OH - ] = 3.3  10 -13 M Acidic or basic? Acidic

8. Ion Product Constant H 2 O H + + OH - H 2 O H + + OH - n Kw is constant in every aqueous. solution [H + ] x [OH - ] = 1 x 10 -14 M 2 n If [H + ] > 10 -7 then [OH - ] 10 -7 then [OH - ] < 10 -7 n If [H + ] 10 -7 n If we know one, we can determine the other. n If [H + ] > 10 -7 acidic [OH - ] 10 -7 acidic [OH - ] < 10 -7 n If [H + ] 10 -7

9. Logarithms n Powers of ten. n A shorthand for big, or small numbers. n pH = -log[H + ] n in neutral pH = - log(1 x 10 -7 ) = 7 n in acidic solution [H + ] > 10 -7 n pH < -log(10 -7 ) n pH < 7 n in base pH > 7

10. pH and pOH n pOH = - log [OH - ] n [H + ] x [OH - ] = 1 x 10 -14 M 2 n pH+pOH = 14

11. 013579111314 013579111314 Basic 10 0 10 -1 10 -3 10 -5 10 -7 10 -9 10 -11 10 -13 10 -14 Basic 10 0 10 -1 10 -3 10 -5 10 -7 10 -9 10 -11 10 -13 10 -14 AcidicNeutral [OH - ] pH [H + ] pOH

12. pH = -log[H 3 O + ] pH Scale pH Scale 0 7 INCREASING ACIDITY NEUTRAL INCREASING BASICITY 14 pouvoir hydrogène (Fr.) “hydrogen power”

13. pH Scale pH Scale pH of Common Substances

14. pH Scale pH = -log[H 3 O + ] pOH = -log[OH - ] pH + pOH = 14

15. pH Scale pH Scale n What is the pH of 0.050 M HNO 3 ? pH = -log[H 3 O + ] pH = -log[0.050] pH = 1.3 Acidic or basic? Acidic

16. pH Scale n What is the molarity of HBr in a solution that has a pOH of 9.6? pH + pOH = 14 pH + 9.6 = 14 pH = 4.4 Acidic pH = -log[H 3 O + ] 4.4 = -log[H 3 O + ] -4.4 = log[H 3 O + ] [H 3 O + ] = 4.0  10 -5 M HBr

17. Types of Acids and Bases Several Definitions

18. Arrhenius Definition n Acids produce hydrogen ions in aqueous solution. n Bases produce hydroxide ions when dissolved in water. n Limits to aqueous solutions. n Only one kind of base. n NH 3 ammonia could not be an Arrhenius base.

19. Definition Arrhenius - In aqueous solution… Arrhenius - In aqueous solution… –Bases –Bases form hydroxide ions (OH - ) NH 3 + H 2 O  NH 4 + + OH - H H H H H H N NO O – + H H H H base

20. Polyprotic Acids n Some compounds have more than 1 ionizable hydrogen. n HNO 3 nitric acid - monoprotic n H 2 SO 4 sulfuric acid - diprotic - 2 H + n H 3 PO 4 phosphoric acid - triprotic - 3 H +

21. Bronsted-Lowry Definitions n And acid is an proton (H + ) donor and a base is a proton acceptor. n Acids and bases always come in pairs. n HCl is an acid. n When it dissolves in water it gives its proton to water. n HCl(g) + H 2 O(l) H 3 O + + Cl - n Water is a base makes hydronium ion.

22. Bronsted-Lowry Definitions n Brønsted-Lowry HCl + H 2 O  Cl – + H 3 O + –Acids –Acids are proton (H + ) donors. –Bases –Bases are proton (H + ) acceptors. conjugate acid conjugate base baseacid

23. Bronsted-Lowry Definitions F - H 2 PO 4 - H2OH2OH2OH2O HF H 3 PO 4 H 3 O + n Give the conjugate base for each of the following: n Polyprotic - an acid with more than one H +

24. Bronsted-Lowry Definitions Br - HSO 4 - CO 3 2- HBr H 2 SO 4 HCO 3 - n Give the conjugate acid for each of the following:

25. Come in Pairs n General equation n HA(aq) + H 2 O(l) H 3 O + (aq) + A - (aq) n Acid + Base Conjugate acid + Conjugate base n This is an equilibrium. n B(aq) + H 2 O(l) BH + (aq) + OH - (aq) n Base + Acid Conjugate acid + Conjugate base n NH 3 (aq)+H 2 O(l) NH 4 + (aq)+OH - (aq)

26. How Strong

27. Strength n Strong acids and bases are strong electrolytes n They fall apart completely. n Weak acids don’t completely ionize. n Concentrated much dissolved. n Strong forms may ions when dissolved. n Mg(OH) 2 is a strong base- it falls completely apart when dissolved. n Not much dissolves.

28. Measuring strength n Ionization is reversible. n HAH + + A - n makes an equilibrium. n Equilibrium constant for an acid(acid dissociation constant. n K a = [H + ][A - ] [HA] n Stronger acid- more products. n larger K a (pg 450)

29. What about bases? n Strong bases dissociate completely. n B + H 2 O BH + + OH - n Base dissociation constant. n K b = [BH + ][OH - ] [B]we can ignore the water n Stronger base more dissociated. n Larger K b.

30. Practice n Write the expression for HNO 2 n Write the K b for NH 3

31. Neutralization reactions

32. Neutralization Reactions Acid + Base  Salt + water Acid + Base  Salt + water n Salt = an ionic compound n Water = HOH HNO 3 + KOH  HNO 3 + KOH  HCl + Mg(OH) 2  HCl + Mg(OH) 2  H 2 SO 4 + NaOH  H 2 SO 4 + NaOH  n Really just double replacement.

33. Reactions Happen in Moles n How many moles of HNO 3 are need to neutralize 0.86 moles of KOH? n How many moles of HCl are needed to neutralize 3.5 moles of Mg(OH) 2 ?

34. Usually happen in solutions n If it takes 87 mL of an HCl solution to neutralize 0.67 moles of Mg(OH) 2 what is the concentration of the HCl solution? n If it takes 58 mL of an H 2 SO 4 solution to neutralize 0.34 moles of NaOH what is the concentration of the H 2 SO 4 solution?

35. Titration Determining an unknown

36. Neutralization n Chemical reaction between an acid and a base. n Products are a salt (ionic compound) and water.

37. Neutralization ACID + BASE  SALT + WATER HCl + NaOH  NaCl + H 2 O HC 2 H 3 O 2 + NaOH  NaC 2 H 3 O 2 + H 2 O –Salts can be neutral, acidic, or basic. –Neutralization does not mean pH = 7. weak strong neutral basic

38. Titration n Titration –Analytical method in which a standard solution is used to determine the concentration of an unknown solution. standard solution unknown solution

39. n Equivalence point (endpoint) –Point at which equal amounts of H 3 O + and OH - have been added. –Determined by… indicator color change Titration dramatic change in pH

40. Titration moles H 3 O + = moles OH - M  V  n = M  V  n M:Molarity V:volume n:# of H + ions in the acid or OH - ions in the base

41. Titration n 42.5 mL of 1.3 M KOH are required to neutralize 50.0 mL of H 2 SO 4. Find the molarity of H 2 SO 4. H3O+H3O+H3O+H3O+ M = ? V = 50.0 mL n = 2 OH - M = 1.3M V = 42.5 mL n = 1 MV# = MV# M(50.0mL)(2)=(1.3M)(42.5mL)(1) M = 0.55M H 2 SO 4

42. Titration n When you add the same number of moles of acid and base, the solution is neutral. n By measuring the amount of a base added you can determine the concentration of the acid. n If you know the concentration of the base. n This is a titration.

43. Normality n Want moles of H + and OH - n molarity x liters = moles of acid or base n Don’t want moles of acid or base n Want moles of H + and OH - n Moles H + = Molarity x liters x # of H + n Normality = Molarity x # of H + n Normality x Liters = Moles of H + n Same process for base yields

44. Titration equations n M a x V a x # of H + = M b x V b x # of OH - n N a x V a = N b x V b n really moles of H + = moles of OH -

45. Practice n What is the normality of the following. n 2.0 M hydrofluoric acid n 0.18 M phosphoric acid n 4.0 M potassium hydroxide n 0.0020 calcium hydroxide

46. More Practice n If it takes 45 mL of a 1.0 M NaOH solution to neutralize 57 mL of HCl, what is the concentration of the HCl ? n If it takes 67 mL of 0.500 M H 2 SO 4 to neutralize 15mL of Al(OH) 3 what was the concentration of the Al(OH) 3 ? n How much of a 0.275 M HCl will be needed to neutralize 25mL of.154 M NaOH?