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Introduction to Acids, Bases and Salts

Introduction to Acids, Bases and Salts. Arrhenius Definition of Acids and Bases. Acids produce H + in aqueous (water) solutions water HCl H + (aq) + Cl - (aq) Bases produce OH - in aqueous (water) solutions water NaOH Na + (aq) + OH - (aq).

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Introduction to Acids, Bases and Salts

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  1. Introduction to Acids, Bases and Salts

  2. Arrhenius Definition of Acids and Bases Acids produce H+ in aqueous (water) solutions water HCl H+ (aq) + Cl- (aq) Bases produce OH- in aqueous (water) solutions water NaOH Na+ (aq) + OH- (aq)

  3. The Hydronium Ion (H30+) • Acids produce the H+ ion • This is just a “bare proton” and is very reactive. • It immediately forms a coordinate covalent bond with nearby water molecules to form (H30+).

  4. Acids Produce H+ (as H3O+) ions in water Electrolytes (conduct in solution) Taste sour pH is < 7 Corrode metals (see Table J) React with bases to form salts and water (Neutralization)

  5. Bases Produce OH- ions in water Electrolytes (conduct in solution) Taste bitter, chalky pH is >7 Feel soapy, slippery React with acids to form salts and water (Neutralization)

  6. Learning Check Describe the solution in each of the following as: 1) acid 2) base or 3)neutral. A. ___soda B. ___soap C. ___coffee D. ___ wine E. ___ water F. ___ grapefruit

  7. Solution Describe each solution as: 1) acid 2) base or 3) neutral. A. _1_ soda B. _2_ soap C. _2_ coffee D. _1_ wine E. _3_ water F. _1_ grapefruit

  8. Learning Check Identify each as characteristic of an A) acid or B) base ____ 1. Sour taste ____ 2. Produces OH- in aqueous solutions ____ 3. Chalky taste ____ 4. Is an electrolyte ____ 5. Produces H+ in aqueous solutions

  9. Solution Identify each as a characteristic of an A) acid or B) base _A_ 1. Sour taste _B_ 2. Produces OH- in aqueous solutions _B_ 3. Chalky taste A, B4. Is an electrolyte _A_ 5. Produces H+ in aqueous solutions

  10. Some Common AcidsSee Table K HCl hydrochloric acid HNO3 nitric acid H3PO4 phosphoric acid H2SO4 sulfuric acid HC2H3O2 acetic acid

  11. Naming Acids (Honors) • Binary Acids • (Contain 2 elements only) • Ex: HCl, HBr, H2S, HF • Hydro __________ ic Acid

  12. Naming Acids (Honors) • Ternary Acids • (Contain hydrogen and a polyatomic ion) • Do NOT start with “Hydro” • Look at name of polyatomic ion • If it ends in “ate” the acid ends in “ic” • If it ends in “ite” the acid ends in “ous”

  13. HBr HNO3 H3PO4 HNO2 H2C2O4 HClO HBrO HClO4 H2S HIO3 Name These Acids

  14. HBr = hydrobromic acid HNO3 = nitric acid H3PO4 = phosphoric acid HNO2 = nitrous acid H2C2O4 = oxalic acid HClO = hypochlorous acid HBrO = hypobromous acid HClO4 = perchloric acid H2S = hydrosulfuric acid HIO3 = iodic acid Name These Acids

  15. Organic Acids • Contain carbon • Only one of the hydrogens is “acidic” and dissociates in solution • Ex: Acetic Acid • HC2H3O2 or CH3COOH

  16. Naming Bases • Name them like any other ionic compound. • Name usually ends in “hydroxide” • Ex: LiOH = lithium hydroxide

  17. Some Common BasesSee Table L NaOH sodium hydroxide KOH potassium hydroxide Ba(OH)2 barium hydroxide Mg(OH)2 magnesium hydroxide Al(OH)3 aluminum hydroxide

  18. Important Note • There are no “organic bases” (containing carbon). C2H5OH for example is not a base. It is an alcohol. The OH on this molecule does not dissociate to form OH- (hydroxide ion)

  19. Salts • “Salts” are ionic compounds that are not acids or bases. • Metal cation (+) & nonmetal anion (-) • They are electrolytes • Ex: NaCl, MgSO4, Li2S

  20. Learning Check Acid, Base Name or Salt CaCl2 ______ _______________ KOH ______ _______________ Ba(OH)2 ______ _______________ HBr ______ _______________ H2SO4 ______ ________________

  21. Answers Acid,Base Name or Salt CaCl2 salt calcium chloride KOH base potassium hydroxide Ba(OH)2 base barium hydroxide HBr acid hydrobromic acid H2SO4 acid sulfuric acid

  22. Dissociation • Dissociation: when a compound splits apart into ions in solution. How might these dissociate? H2SO4 KOH

  23. Acids React with Metals • See Reference Table J • Metals above Hydrogen on the table will react with acids to form a salt and H2 gas • Single Replacement Reaction 2Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)

  24. Will an acid react with these metals? • If so complete and balance the single replacement reaction. Mg + HNO3 Cu + HCl Ca + H2SO4

  25. Answers Mg + 2HNO3 Mg(NO3)2 + H2 Cu + HCl No reaction Cu in below hydrogen on Table J Ca + H2SO4 Ca(SO4) + H2

  26. Acid, Bases and Metals BBC (good for Indicators) • http://www.bbc.co.uk/schools/ks3bitesize/science/chemical_material_behaviour/acids_bases_metals/activity.shtml

  27. Pure Water is Neutral Self Ionization of Water: a small quantity of water molecules in a sample will self ionize. This results in a small, but equal amount of H+ and OH- H2O H+ + OH- Hydrogen Ion = Hydroxide Ion [H+] = [OH-] H+ OH-

  28. Self Ionization of Water http://youtu.be/kW-Zk4zABzw

  29. Acids Increase the H+ concentration As H+ increases, OH- decreases [H+] > [OH-] H+ OH-

  30. Bases Increase the hydroxide ion (OH-) concentration When OH- increases, H+ decreases [OH] > [H+] OH- H+

  31. Important Summary • Acidic: [H+] > [OH-] • Basic: [H+] < [OH-] • Neutral: [H+] = [OH-]

  32. Determining if it is an Acid or Base • How can you tell if something is acidic or basic?

  33. Use an electronic pH meter

  34. Use an indicator such as litmus

  35. Use pH paper containing universal indicator

  36. Acid/Bases IndicatorsSee Table M Examples: • Litmus • pH range for color change (4.5 – 8.3) • Color change: red to blue • Phenolphthalein • pH range for color change (8 - 9) • Color change: colorless to pink What color would these be if the pH = 10? pH = 3?

  37. pH Scale 0 1 2 3 4 5 6 7 8 910 11 12 13 14 Neutral [H+]>[OH-][H+] = [OH-][OH-]>[H+] Acidic Basic

  38. Pretty Hydrangeas • The color of hydrangea flowers depends on the pH of the soil.

  39. What is pH? • Tells us the relative quantity of H+ ions (or the acidity) in solution. • The greater the [H+] the lower the pH.

  40. Calculating pH pH = - log [H+] From the French pouvoir hydrogene (“hydrogen power” or power of hydrogen)

  41. [H+] pH 1 x 10-5 M 5 1 x 10-9 M 9 1 x 10-11M 11

  42. Calculating pOH • What if you are given the concentration of a base? • Ex: .000001M LiOH You need to find the pOH!!

  43. pOH pOH = -log [OH-] Ex: .000001M LiOH = 1 x 10-6 pOH = 6 Ex: .0001M NaOH = 1 x 10-4 pOH = 4

  44. How can you find pH of a Base? • Easy!!! pH + pOH = 14 Ex: .000001M LiOH = 1 x 10-6 pOH = 6 pH = 8 Ex: .0001M NaOH = 1 x 10-4 pOH = 4 pH = 10

  45. Kw If you know the concentration of one ion you can find the other! [H+] x [OH-] = 1 x 10-14 This is called the Kw Or the “ion product” of water.

  46. So what is the [OH-] is the [H+] is .001M? [1 x 10-3] x [OH-] = 1 x 10-14 [OH-] = 1 x 10-11 Everything keeps adding up to 14!! What’s up with that?

  47. Let’s Try It You have a .001 HCl solution. Find: [H+], [OH-], pH, pOH

  48. Let’s Try It You have a .000000001M NaOH solution. Find: [H+], [OH-], pH, pOH

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