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Ch # 6

Ch # 6. Acids, Bases and Salts. ACIDS. An acid “is a hydrogen-containing substance that produces hydrogen ions” in water. (Hydronium ion: H 3 O + ) An aqueous solution that contains more H + ions than OH - ions is ‘acidic’. ACID PROPERTIES. Sour taste (think lemons and sour candies)

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Ch # 6

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  1. Ch # 6 Acids, Bases and Salts

  2. ACIDS • An acid “is a hydrogen-containing substance that produces hydrogen ions” in water.(Hydronium ion: H3O+) • An aqueous solution that contains more H+ ions than OH- ions is ‘acidic’

  3. ACID PROPERTIES • Sour taste (think lemons and sour candies) • Change the color of litmus from blue to red.

  4. Acid Properties (cont.) • React with a base to produce water and salt in a double displacement neutralization reaction. • React with metals such as zinc and magnesium to produce hydrogen gas in a single replacement reaction.

  5. BASES • An base is a hydroxide-containing substance that dissociates to produce hydroxide ions in aqueous solution. • An aqueous solution that contains more OH- ions than H+ ions is ‘basic’

  6. BASE PROPERTIES • Bitter or caustic taste. • A slippery, soapy feeling. • The ability to change litmus red to blue. • The ability to interact with acids in a neutralization reaction to produce water and salt.

  7. Ionization/Dissociation. • Ionization: A process in which ions are produced from a molecular compound when dissolved in a solvent. ACIDS • Dissociation: A process in which already existing ions in an ionic compound separate when an ionic compound is dissolved in a solvent. BASES

  8. Amphoteric substances • Glycine • Hydrogen carbonate

  9. Other kinds of acids and bases • FeCl3A metal ion that is acidic • CO32- An anion that is basic • NH4+A cation that is acidic

  10. Salts • A salt is an ionic compound containing a metal cation and a nonmetal anion • Produced in a neutralization reaction: HCl + NaOH H2O + NaCl

  11. 6.3 Conductance of A, B, S Solutions • Strong electrolyte • Weak electrolyte • Non-electrolyte

  12. 6.4 Dissociation of A & B • Strong acids & bases – strong electrolyte • Weak acids & bases – weak electrolyte

  13. 6.5 Buffers • A solution that resists major changes in pH when small amounts of acid or base is added to it.1) A substance to react with and remove added base. • 2) A substance to react with and remove added acid. • 3) weak acid-salt.

  14. 6.6 pH and Acidic / Basic Solutions

  15. Self ionization of water: • Ion product constant for water: • Kw = [H3O+] [OH-] = 1.00 x 10-14 • If [H3O+] = 7.50 x 10-5 M What is the [OH-] in this solution?

  16. pH = -log [H3O+] = -log [H+]

  17. H3O+

  18. Acidic solution: [H3O+]> [OH-] pH= 0-6 • Basic solution: [H3O+]< [OH-] pH =8-14 • Neutral solution: [H3O+]= [OH-] pH =7 • pH scale: Scale that is used to specify molar hydronium ion concentration in an aqueous solution.

  19. Problems Calculate pH for the following and identify as acidic or basic: [H3O+] = 1 X 10-3 [H3O+] = 1 X 10-9 [OH-] = 1 X 10-4 [H3O+] = 3.9 X 10-5 [H3O+] = 7.9 X 10-11 The number of decimal places of a logarithm is equal to the number of significant figures in the original number.

  20. Problem The pH of a solution is 5.70. What is the molar hydronium ion concentration for this solution? [H3O+] = 10-pH

  21. 6.7 Preparation of Acids • H2(g) + Cl2(g) 2HCl(g) • 2NaCl + H2SO4 2HCl(g) + Na2SO4 • SO2(g) + H2O  H2SO3

  22. 6.8 Preparation of bases: • Alkali metal and water to produce hydrogen and a hydroxide salt. • Ammonia in water • Carbonate in water

  23. 6.9 Preparation of Salts • The reaction of an acid with a base is called a neutralization reaction. In an aqueous solution the products are a salt and water. • Solvay process for making NaHCO3 and Na2CO3 (p226)

  24. Reactions of salts: Reaction with metals: Single replacement reaction according to activity series. • Reaction with acids: Double displacement reaction. A new weaker acid, new insoluble salt, gaseous compound is one of the products. • Reaction with bases: Insoluble precipitate forms, or weaker base. • Reaction of salts with each other: Double displacement reaction. Insoluble salt is formed.

  25. 6.10 Acidic and Basic Salts • Ions that contain H+ • Bases: See Page 213 • Hydroxyapatite Ca5OH(PO4)3 • Reactions: NaHCO3 + NaOH Na2CO3 + H2O

  26. 6.11 Water of Hydration • Water binds to some salts: • These are hydrates. They are used as desiccants (drying agents). • A desiccant is a hygroscopic substance that induces or sustains a state of dryness (desiccation) in its vicinity. • Anhydrous (without water of hydration)

  27. Examples and names CaSO4▪2H2O calcium sulfate dihydrate (gypsum-dry wall, plaster of paris, Dri-rite) CuSO4▪5H2O copper(II) sulfate pentahydrate

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