3. Essential Questions: What are the characteristics of an acid and a base? What is a salt? Characteristics of Acids: Have a sour taste Ex: acetic acid (vinegar) Have a sour taste Ex: acetic acid (vinegar) Change color with an acid-base indicator Change color with an acid-base indicator Aqueous solutions of acids are electrolytes (weak/strong). Aqueous solutions of acids are electrolytes (weak/strong). Aqueous solutions conduct an electrical current. Aqueous solutions conduct an electrical current. The more ions in a solution the stronger the electrolyte(stronger the acid). The more ions in a solution the stronger the electrolyte(stronger the acid). The less ions in a solution the weaker the electrolyte(weaker acid). The less ions in a solution the weaker the electrolyte(weaker acid).

4. ►A►A►A►Acids react with a base to form a salt and water (neutralization reaction). Ex: Acid + BaseSalt + Water ► S► S► S► Salt- product of a neutralization reaction ►R►R►R►React with certain metals to produce H2 gas. * Table J- those metals that are above H2 will react to produce H2 and a salt. Ex: Mg + 2HClMgCl2 + H2 Cu + HCl No reaction

6. Where have you seen an acid? Citric acid- citrus fruit Ascorbic acid- vitamin C Phosphoric acid- Coke Acetic acid- vinegar Hydrochloric acid- lab (and stomach)

8. Characteristics of Bases: H Have a bitter taste. Ex: soap C Change the color of an acid-base indicator. F Feel slippery A Aqueous solutions of acids can be strong or weak electrolytes. Bases conduct an electrical current. Ex: Bases with large number of ions in solution are strong bases B Bases react with an acid and acid to produce a salt and water (neutralization reaction) A Are caustic

10. Common bases:

11. Why are some acids and bases strong and others weak?  A strong acid or base produces lots of ions.  Strong Acid: completely ionizes  A weak acid produces very few ions.  Bases behave similarly.

13. Essential Question: What are the three theories of Acid and Bases ? Theories of Acids/Bases: A. Arrhenius B. Bronsted-Lowry

14. Write a neutralization reaction. Label all parts of the equation. Remember Tables L and K are your friends.

15. Arrhenius (Swedish chemist 1859-1927): Arrhenius (Swedish chemist 1859-1927): Proposed that acids are hydrogen-containing compounds Proposed that acids are hydrogen-containing compounds that ionize to yield hydronium ion in solution in an aqueous solution. Exs: a. HCl(aq)  H + (aq) + Cr - (aq) b. H+ + H 2 0  H 3 O + ( Hydronium) b. H+ + H 2 0  H 3 O + ( Hydronium) c. HCl(aq)  H 3 o + + Cl - H + combines to form H 3 O + H + combines to form H 3 O + Only H in very polar bonds are ionizable Only H in very polar bonds are ionizable CH 4 ( methane )- has no ionizable H and is not an acid. Very weak polar bonds. CH 4 ( methane )- has no ionizable H and is not an acid. Very weak polar bonds. *Not all substances that contain H are acids. However entanoic acid(CH 3 COOH) *Not all substances that contain H are acids. However entanoic acid(CH 3 COOH) Nature of H ion: H  H+ + le-

16. Let’s do some definitions: Arrhenius acid: Arrhenius acid: Producer of H + ion in solution Producer of H + ion in solution HCl HCl H 2 SO 4 (2 H + ’s) H 2 SO 4 (2 H + ’s) Arrhenius base: Arrhenius base: Producer of OH - in solution Producer of OH - in solution NaOH NaOH KOH KOH

17. Essential Question: What are monprotic, diproitic and triprotic acids? Monoprotic Acid- acids that contain one ionizable hydrogen. Ex: HNO 3 Diprotic Acid -acids that contain two ionizable hydrogens Ex: H 2 SO 4 H 2 SO 4  H+ + HSO 4 HSO 4  H+ + SO4 -2 Triprotic acid- acids that contain three ionzable hydrogens Ex:H 3 PO 4

18. Bases B. Bases are compounds that ionize to yield hydroxide ions (OH - ) in aqueous solution. Ex: NaOH(s)  Na(aq) + + OH(aq) -

19. Example of some Bases: NaOH: 1. Also known as lye 2. Used to clean clogged drains 3. Very caustic 4. Very soluble in water. Mg(OH)2: 1. Not very soluble in water. 2. Used in milk of magnesia (antacid and mild laxative)

20. B. Bronsted-Lowry Acid/Base Theory: 1. Proposed by Johannes Bronsted (Danish chemist and Thomas Lowry (English chemist) in 1923. 1. Proposed by Johannes Bronsted (Danish chemist and Thomas Lowry (English chemist) in 1923. 2. Define an acid as a H+ donor and a base as a H + ion acceptor. Ex: NH 3 (aq) + H 2 0 (l) NH 3 (aq) + OH - (aq) NH 3 (aq) + OH - (aq) 3. More compressive than Arrhenius theory.

21. BASES… what do they do? Bronsted-Lowry definition: BASES ACCEPT H + IONS. Arrhenius definition: bases produce OH - ions in solution  Ammonia… weak base. NaOH  Strong base.

22. Bronsted-Lowry: the better definition Bronsted- Lowry acid: Bronsted- Lowry acid: Acids donate protons (H + ) Acids donate protons (H + ) HCl  H + + Cl - HCl  H + + Cl - Bronsted- Lowry base: Bronsted- Lowry base: Bases accept protons (H + ions) NH 3 + H +  NH 4 + NH 3 + H +  NH 4 + OH - + H +  H 2 O OH - + H +  H 2 O

23. Let’s find the donors and acceptors in the following rxns. H 2 O + NH 3  NH 4 + + OH - H 2 O + NH 3  NH 4 + + OH - acidbase(water donates H + to NH 3 ) acidbase(water donates H + to NH 3 ) HCl + H 2 O  H 3 O + + Cl - HCl + H 2 O  H 3 O + + Cl - Acidbase (water accepts H + ) Acidbase (water accepts H + ) Water is amphoteric; it can act as an acid or a base. Water is amphoteric; it can act as an acid or a base. How about: HNO 3 + NH 3  NO 3 - + NH 4 + How about: HNO 3 + NH 3  NO 3 - + NH 4 +

24. Can you identify the donors (acids) and acceptors (bases)? HS + HF  F - + H 2 S Acceptor(base)Donor(acid)

25. One more time… HCl +NH 3   NH 4 + + Cl- Donor(acid)Acceptor(base)

26. Summary of Acid/Base Definitions: ACIDSBASES Says who? Produces H + ions in solution Produces OH - ions in solution Arrhenius Proton (H + )donor Proton (H + ) acceptor Bronsted-Lowry HCl + NH 3  Cl - + NH 4 + Acid base

27. How do we measure the strength of acids? We find the concentration of H + ions. We find the concentration of H + ions. Symbolically [H + ] or [H 3 O + ] Symbolically [H + ] or [H 3 O + ] H + and H 3 O+ represent the same thing. H + and H 3 O+ represent the same thing. [H + ] usually very small [H + ] usually very small If [H + ] is 0.1 M, you have a very strong acid If [H + ] is 0.1 M, you have a very strong acid If [H + ] is 0.001 M, you have a weak acid If [H + ] is 0.001 M, you have a weak acid Water contains a small amount of H + Water contains a small amount of H + [H + ] of water ~ 10 -7 M [H + ] of water ~ 10 -7 M

28. Why are some acids and bases strong and others weak? A strong acid or base produces lots of ions. A strong acid or base produces lots of ions. Strong Acid: completely ionizes Strong Acid: completely ionizes A weak acid produces very few ions. A weak acid produces very few ions. Bases behave similarly. Bases behave similarly.

29. Essential Questions: What is the pH scale? How do you determine the pH of a solution? pH Scale: 1. Proposed by Sorensen in 1909. 2. Scale of 0-14 3. Based on the concentration of H+ ions 4. Scale is logarithmic, thus each change of a single pH units signifies a tenfold change in concentration.

30. We use the [H+] to find pH of acids and bases: pH = -log [H + ] [H + ] = 10 -1 (very acidic) [H + ] = 10 -1 (very acidic) [H + ] = 10 -3 (acidic) [H + ] = 10 -3 (acidic) [H + ] = 10 -5 [H + ] = 10 -5 [H + ] = 10 -7 (pure water) [H + ] = 10 -7 (pure water) [H + ] = 10 -9 (basic) [H + ] = 10 -9 (basic) [H + ] = 10 -11 (very basic) [H + ] = 10 -11 (very basic) Lets find some: Lets find some: 1. pH= 1 2. pH= 3 3. pH= 5 4. pH = 7 5. pH= 9 6. pH = 11

31. The concentration of H+ is ten times greater in solution with a pH of 5 as in a solution with a pH pf 6. pH: 0-6.9 acidic 7 neutral 7.1 -14 basic 5. pH = -log H +

34. Exs: A solution with a pH of 9, H + = l x lO -9 M A solution with a pH of 4, H+ =1 x 10 -4 pH Problems: What is the pH of the following?: H+= l xlO -4 M pH = -log H + pH = -log (l x 10 -4 ) pH =4.0

35. pOH: 1. negative log of the OH- ions 2. pOH = -log OH- pH + pOH=14 pH=14-pOH or pOH =14-pH Ex: What is the pOH of a solution with a H+ = of 1.0 x 10-4M? pH=4 14-4 =POH 10=pOH

36. Essential Questions: What is an acid-Base indicator? What is the relationship of Table M to indicators? Acid-Base Indicators: 1. Substance that changes its color when it gains or loses a proton. Ex: Phenolphthalein (Hln) Hln is colorless when it contains a H atom. When a base is gradually added to an acid containing Hln, the solution is initially colorless. Once the acid has been neutralized by the addition of the base, the base reacts with the H atom of the indicator. Hln turns pink. Shows when a titration has reached an endpoint. Hln  H + + In

37. Table M Indicators are chemicals that have certain characteristic color’ depending on the pH. They can be used to determine if solution is acidic or basic, or even to narrows the range of pH of a solution down. Methyl orange is RED from a pH of 3.2 or lower, and YELLOW from a ph of 4.4 or more. The middle of the range is an intermediate color (in this case,ORANGE).

38. 2. Table M lists several indicators and color changes they undergo, and the pH range over which the color change occurs. 3. Indicators tend to have distinct colors at each of their useful pH range and pass thru intermediate color region that is a mixture of these two colors.

39. Essential Questions: What is neutralization? What is a salt? Acid-Base Reactions: Neutralization: 1. Reaction between an acid and a base in which a salt and water are produced. Exs: HCl(aq) + NaOH(aq)  NaCl(aq) + H 2 0(l) H 2 SO 4 (aq) + 2KOH(aq)  K 2 SO 4 (aq) +2H 2 0 H 2 SO 4 (aq) + 2KOH(aq)  K 2 SO 4 (aq) +2H 2 0

40. Method of obtaining pure samples of a salt Method of obtaining pure samples of a salt 3. Neutralization reactions are in specific ion-to-ion or mole-to-mole ratios. Exs: Exs: HC(aq) + NaOH(aq)  NaCl(aq) + H 2 0(l) 1:1:1:1 ratio 1:1:1:1 ratio

41. Salt: 1. Compounds consisting of anion from an acid and a cation from a base 2. Doesn't have any of the characteristics of the acid or base. 3. Used to make antacids and the neutralization of pH of soil.

42. What happens when I mix acids and bases? Acids and bases neutralize each other. One of the solutions is a known concentration Using its volume determines the concentration of the unknown. Technique is called TITRATION Aka neutralization

43. Essential Questions: What is titration? What is a standard solution? What is the endpoint? What is the formula for titration? Titration: 1. Process of adding measured volumes of an acid or abase of known concentration to an acid or base of unknown concentration until neutralization occurs. 2. Used to determine the concentration of an unknown acid or base. Standard solution-solution with known concentration Endpoint- point at which indicator turns a color

44. An ACID and BASE react to Neutralize each other. Double replacement reaction For any neutralization: ACID + BASE  Water + SALT NaOH(aq) + HNO 3 (aq)  NaNO 3 (aq) + H 2 O BASE ACIDSALTWATER

45. : 1. Add a measured volume of an acid with unknown concentration to a flask 2. Add several drops of indicator to the solution in the flask 3. Add measured volumes of base with known concentration into the acid until indicator just barely changes color.

46. We will be using phenolphthalein (PHTH). It is colorless in acid. When you add the base to the acid it begins to turn pink. When the pink stays, you are at the endpoint.

49. How do I find the unknown volume or concentration? An acid and base neutralize each other via a double replacement reaction An acid and base neutralize each other via a double replacement reaction Acid+ base  salt + waterAcid+ base  salt + water NaOH + HCl  NaCl + HOHNaOH + HCl  NaCl + HOH Ion swap!! Ion swap!! KOH + HNO 3  KNO 3 + HOH KOH + HNO 3  KNO 3 + HOH Always H + + OH -  H 2 O Always H + + OH -  H 2 O

50. Titration Problems: MA x VA = MB x VB M=moles of solute Liters of solution Ex: What is the concentration of hydrochloric acid solution if 50.0 ml of 0.250 M KOH are needed to neutralize 20.C ml of the HC1 solution of an unknown concentration? Known: Unknown: MKOH=.250M M of HCl VA = 20. 0 ml VB = 50.0 ml KOH +HCl H20 +KC1 MA x VA = MB x VB MA= MBxVB VA MA = 250M (50.0ml) 20.0 ml MA=.625 M

51. What is the concentration of a sulfuric acid solution if 50.0 ml of 0.250 M KOH are needed to neutralize 20.0 ml of theH2S04 solution of an unknown concentration? 2KOH + H 2 S0 4  2H 2 0 + K 2 S0 4 M A x V A = M B x V B M A = M B x V B V A V A M A =.250M x 50.0ml 2.0ml 2.0ml M A =.625 M Molarity H 2 S04 =H + =.625M=.31 M 2 2 2 2