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Introduction to Acids, Bases

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

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Introduction to Acids, Bases

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  1. Introduction to Acids, Bases

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

  3. Dissociation • Dissociation: when a compound splits apart into ions in solution. How might these dissociate? H2SO4 KOH DO NOW: Packet page 3, #7 Practice Writing Dissociation Equations

  4. Note: • Acids and Bases are only reactive if their ions are dissociated (when aqueous) • HCl (l) = hydrogen chloride • HCl (aq) = hydrochloric acid

  5. Getting to Know Some Acids

  6. Some Common AcidsSee Table K HCl hydrochloric acid HNO3 nitric acid H3PO4 phosphoric acid H2SO4 sulfuric acid HC2H3O2 acetic acid 6

  7. 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+). Do Now: Draw the formation of the Hydronium Ion

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

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

  10. 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”

  11. HBr HNO3 H3PO4 HNO2 H2C2O4 HClO HBrO HClO4 H2S HIO3 Name These Acids (Honors)

  12. 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 (Honors)

  13. Getting to Know Some Bases

  14. Naming Bases • All Arrhenius bases contain the hydroxide ion • Name ends in “hydroxide” • Ex: LiOH = lithium hydroxide • Note: • There are “Non” Arrhenius Bases, more on them later

  15. 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 15

  16. 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)

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

  18. Learning Check Acid, Base Name or Salt CaCl2 ______ _______________ KOH ______ _______________ Ba(OH)2 ______ _______________ HBr ______ _______________ H2SO4 ______ ________________ 18

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

  20. Electrolytes • Acids & Bases & Salts are electrolytes • Produce free ions when dissolved • Solutions will conduct. • More concentrated = more conductive. Do Now: Practice Ditto on Identifying Electrolytes http://www.kentchemistry.com/links/AcidsBases/Electrolytes.htm

  21. Taste & Feel • Acids: taste sour and give a burning sensation if touched • Bases: taste bitter and feel slippery if touched DO NOT attempt to determine an acid or base by taste or touch ever in the lab!

  22. Let’s Review • Which substance, when dissolved in water, forms a solution that conducts an electric current? (1) C2H5OH     (3) C12H22O11(2) C6H12O6 (4) CH3COOH

  23. A solid substance was tested in the laboratory. The test results are listed below.• dissolves in water• is an electrolyte• melts at a high temperature Based on these results, the solid substance could be (1) Cu               (3) C (2) CuBr2 (4) C6H12O6

  24. The compound HNO3 can be described as an (1) Arrhenius acid and an electrolyte (2) Arrhenius acid and a nonelectrolyte (3) Arrhenius base and an electrolyte (4) Arrhenius base and a nonelectrolyte

  25. Based on Reference Table F, which of these salts is the best electrolyte? A. sodium nitrate B. magnesium carbonate C. silver chloride D. barium sulfate

  26. A substance that conducts an electrical current when dissolved in water is called (1) a catalyst   (2) a non-electrolyte (3) a metalloid    (4) an electrolyte

  27. Which compound is an Arrhenius acid? (1) CaO  (2) K2O (3) HCl   (4) NH3

  28. When one compound dissolves in water, the only positive ion produced in the solution is H3O+(aq). This compound is classified as (1) a salt (2) a hydrocarbon (3) an Arrhenius acid (4) an Arrhenius base

  29. Which substance is an Arrhenius acid? (1) Ba(OH)2 (2) H3PO4 (3) CH3COOCH3 (4) NaCl

  30. Which compound releases hydroxide ions in an aqueous solution? (1) CH3COOH   (2) HCl (3) CH3OH    (4) KOH

  31. An Arrhenius base yields which ion as the only negative ion in an aqueous solution? (1) hydride ion  (2) hydronium ion (3) hydrogen ion      (4) hydroxide ion

  32. The compound NaOH(s) dissolves in water to yield (1) hydroxide ions as the only negative ions (2) hydroxide ions as the only positive ions (3) hydronium ions as the only negative ions (4) hydronium ions as the only positive ions

  33. How are HNO3(aq) and CH3COOH(aq) similar? (1) They are Arrhenius acids and they turn blue litmus red. (2) They are Arrhenius acids and they turn red litmus blue. (3) They are Arrhenius bases and they turn blue litmus red. (4) They are Arrhenius bases and they turn red litmus blue.

  34. Acids “Corrode” Certain 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)

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

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

  37. Bases DO NOT corrode metals • Interactive: • Acid, Bases and Metals BBC (good for Indicators) • http://www.bbc.co.uk/schools/ks3bitesize/science/chemical_material_behaviour/acids_bases_metals/activity.shtml DO NOW: Packet page 2 and 3, # 4, #5

  38. pH Scale • Used to help determine how acidic or basic something is. • pH = 7 Neutral • pH < 7 Acidic • pH > 7 Basic

  39. Acids & Bases Neutralize Each Other • H+ ion and OH- ions will join together to form neutral water. • Reaction is slightly exothermic (See Table I) H+ (aq) + OH- (aq) → H2O (l)

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

  41. Use an electronic pH meter

  42. Use an indicator such as litmus

  43. Use pH paper containing universal indicator

  44. Acid/Bases IndicatorsUsing Table M • 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 • pH = 10? • pH = 3?

  45. Let’s Review Based on the results of testing colorless solutions with indicators, which solution is most acidic? (1) a solution in which bromthymol blue is blue (2) a solution in which bromcresol green is blue (3) a solution in which phenolphthalein is pink (4) a solution in which methyl orange is red

  46. According to Reference Table M, what is the color of the indicator methyl orange in a solution that has a pH of 2? (1) blue  (2) orange (3) yellow  (4) red

  47. Which indicator would best distinguish between a solution with a pH of 3.5 and a solution with a pH of 5.5? (1) bromthymol blue  (2) litmus (3) bromcresol green    (4) thymol blue

  48. Which indicator is blue in a solution that has a pH of 5.6? (1) bromcresol green  (2) methyl orange (3) bromthymol blue   (4) thymol blue

  49. Which indicator is yellow in a solution with a pH of 9.8? (1) methyl orange (2) bromcresol green (3) bromthymol blue  (4) thymol blue

  50. In which solution will thymol blue indicator appear blue? (1) 0.1 M CH3COOH (2) 0.1 M HCl (3) 0.1 M KOH    (4) 0.1 M H2SO4

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