The Chemistry of Acids and Bases

1. The Chemistry of Acids and Bases

2. Acid and Bases

3. Acid and Bases

4. Acid and Bases

5. Some Properties of Acids • Produce H+ (as H3O+) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule) • Taste sour • Corrode metals • Electrolytes • React with bases to form a salt and water • pH is less than 7 • Turns blue litmus paper to red “Blue to Red A-CID”

6. Some Properties of Bases • Produce OH- ions in water • Taste bitter, chalky • Are electrolytes • Feel soapy, slippery • React with acids to form salts and water • pH greater than 7 • Turns red litmus paper to blue “Basic Blue”

7. Some Common Bases Formula Name Common Name NaOH KOH Ba(OH)2 Mg(OH)2 Al(OH)3 sodium hydroxide lye potassium hydroxide liquid soap barium hydroxide stabilizer for plastics magnesium hydroxide “MOM” Milk of magnesia aluminum hydroxide Maalox (antacid)

8. Acid Nomenclature Binary  Ternary An easy way to remember which goes with which… “In the cafeteria, you ATE something ICky”

9. Acid Nomenclature Flowchart

10. Acid Nomenclature Review • HBr (aq) • H2CO3 • H2SO3 hydrobromicacid  carbonicacid  sulfurousacid

11. Try these • Hydroiodic Acid • HI (aq) • HCl (aq) • H2SO4 • HNO3 • H2CO3 • Hydrochloric Acid • Sulfuric Acid • Nitric Acid • Carbonic Acid

12. Try these • Hydrobromic Acid • HBr (aq) • HCN (aq) • H2SO3 • HClO4 • CH3OOH • Cyanic Acid • Sulfurous Acid • Perchloric Acid • Acetic Acid

13. Acid/Base definitions • Definition #1: Arrhenius (traditional) Acids – produce H+ ions (or hydronium ions H3O+) Bases – produce OH- ions (problem: some bases don’t have hydroxide ions!)

14. Arrhenius acid is a substance that produces H+ (H3O+) in water Arrhenius base is a substance that produces OH- in water NaOH + H2O  OH- + Na+ + H2O

15. Acid & Base Definitions • Definition #2: Brønsted–Lowry Acids – proton donor Bases – proton acceptor A “proton” is really just a hydrogen atom that has lost it’s electron! PDA (proton donated acid) BAD (Brønsted–Lowry acid donates)

16. ACID-BASE THEORIES A Brønsted-LowryAcidis a proton donor A Brønsted-LowryBaseis a proton acceptor The Brønsted definition means NH3 is aBasein water — and water is itself anAcid ConjugateBase ConjugateAcid Base Acid

17. Conjugate Pairs Conjugate Acid – the remaining ion or molecule that can re-accept the proton and act as a base Conjugate Base – the species that is formed when a Brønsted-Lowry base gains a proton.

18. Acids & Base Definitions Definition #3 – Lewis Lewis acid - a substance that accepts an electron pair Lewis base - a substance that donates an electron pair

19. Lewis Acids & Bases Formation ofhydronium ion is an excellent example. • Electron pair of the new O-H bond originates on the Lewis base.

20. Acids & Base Definitions Summary

21. SOME DEFINITIONS • Amphoteric - A substance that can act as either an acid or a base, e.g., H2O, HCO3- • Polyprotic acid or base - An acid or base that can donate or accept more than one proton or hydroxide, e.g., H3PO4, H2CO3, H4EDTA…Ba(OH)2, Al(OH)3

22. Strong and Weak Acids/Bases The strength of an acid (or base) is determined by the amount of IONIZATION. • Generally divide acids and bases into STRONG or WEAK

23. Strong and Weak Acids/Bases STRONG ACID: HNO3 (aq) + H2O(l) --> H3O+(aq) + NO3-(aq) HNO3 is about 100% dissociated in water. HNO3, HCl, HBr, HI, H2SO4 and HClO4 are among the only known strong acids.

24. Strong and Weak Acids/Bases • Weak acids are much less than 100% ionized in water. One of the best known is acetic acid = CH3COOH

25. CaO Strong and Weak Acids/Bases • Strong Base:100% dissociated in water. NaOH (aq) ---> Na+ (aq) + OH- (aq) Other common strong bases include KOH andCa(OH)2. CaO (lime) + H2O --> Ca(OH)2 (slaked lime)

26. Strong and Weak Acids/Bases • Weak base:less than 100% ionized in water One of the best known weak bases is ammonia NH3(aq) + H2O(l) NH4+(aq) + OH-(aq)

27. Other Weak Bases

28. The pH scale is a way of expressing the strength of acids and bases. Instead of using very small numbers, we just use the NEGATIVE power of 10 on the Molarity of the H+ (or OH-) ion.Under 7 = acid 7 = neutralOver 7 = base

29. pH of Common Substances

32. 1)Solution A [H3O+] = 5.89 x 10-7 pH = ?2)Solution B [H3O+] = 4.365 x 10-12 pH = ?3)Solution C [H3O+] = 1.05 x 10-4 pH = ?4)Solution D [H3O+] = 1.00 x 10-6 pH = ? Determine the pH of the following H3O+ concentrations

33. 1)Solution A [H3O+] = 5.89 x 10-7 pH = 6.232)Solution B [H3O+] = 4.365 x 10-12 pH = 11.363)Solution C [H3O+] = 1.05 x 10-4 pH = 3.984)Solution D [H3O+] = 1.00 x 10-6 pH = 6.00 Determine the pH of the following H3O+ concentrations

34. pH meter • Tests the voltage of the electrolyte • Converts the voltage to pH • Very cheap, accurate • Must be calibrated with a buffer solution

35. Calculating the pH pH = - log [H+] (Remember that the [ ] mean Molarity) Example: If [H+] = 1 X 10-10pH = - log 1 X 10-10 pH = - (- 10) pH = 10 Example: If [H+] = 1.8 X 10-5pH = - log 1.8 X 10-5 pH = - (- 4.74) pH = 4.74

37. pH calculations – Solving for H+ If the pH of Coke is 3.12, [H3O+] = ??? Because pH = - log [H3O+] then - pH = log [H3O+] Take antilog (10x) of both sides and get 10-pH =[H3O+] [H3O+] = 10-3.12 = 7.59 x 10-4 M *** to find antilog on your calculator, look for “Shift” or “2nd function” and then the log button

38. pOH • Since acids and bases are opposites, pH and pOH are opposites! • pOH is useful for changing bases to pH. • pOH looks at the perspective of a base pOH = - log [OH-] Since pH and pOH are on opposite ends, pH + pOH = 14

39. pH [H+] [OH-] pOH

42. The pH of rainwater collected in a certain region of the northeastern United States on a particular day was 4.82. What is the H+ ion concentration of the rainwater?

43. pH testing • There are several ways to test pH • Blue litmus paper (red = acid) • Red litmus paper (blue = basic) • pH paper (multi-colored) • pH meter (7 is neutral, <7 acid, >7 base) • Universal indicator (multi-colored) • Indicators like phenolphthalein • Natural indicators like red cabbage, radishes

44. pH indicators • Indicators are dyes that can be added that will change color in the presence of an acid or base. • Some indicators only work in a specific range of pH • Once the drops are added, the sample is ruined • Some dyes are natural, like radish skin or red cabbage

45. The pigment in red cabbage juice is anthocyanin, which changes color from red in acid solution to purplish to green in mildly alkaline solution to yellow in very alkaline solution.

46. Other pH Indicators

47. Universal Indicator • Determine the pH to the tenth and ion concentration of the following unknown solution given the color of each indicator: • qPhenolphthalein - colorless • qUniversal indicator – red-orange • qBromcresol Green – yellowish green

48. Universal Indicator • Determine the pH to the tenth and ion concentration of the following unknown solution given the color of each indicator: • qAlzarin Yellow R – yellow • qPhenolphthalein - pink • qThymolphthalein –blue

49. Universal Indicator • Determine the pH to the tenth and ion concentration of the following unknown solution given the color of each indicator: • qMethyl Orange – yellowish orange • qChlorphenol Red – yellow • qBromthymol Blue – yellow • qBromcresol Green – blue

50. Oxalic acid, H2C2O4 ACID-BASE REACTIONSTitrations H2C2O4(aq) + 2 NaOH(aq) ---> acidbase Na2C2O4(aq) + 2 H2O(liq) Carry out this reaction using aTITRATION.