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Acids

Acids. Arrhenius acids produce H + ions in water. are electrolytes. have a sour taste. turn litmus red. neutralize bases. Note acid name endings: -ic (if anion was –ide or –ate) -ous (if anion was –ite). Acids you need to know by name and formula (see Syllabus).

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Acids

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  1. Acids Arrhenius acids • produce H+ ions in water. • are electrolytes. • have a sour taste. • turn litmus red. • neutralize bases.

  2. Note acid name endings: -ic (if anion was –ide or –ate) -ous (if anion was –ite)

  3. Acids you need to know by name and formula (see Syllabus) • Hydrochloric acid = HCl • Hydrofluoric acid = HF • Sulfuric acid = H2SO4 • Phosphoric acid = H3PO4 • Carbonic acid = H2CO3 • Nitric acid = HNO3 • Acetic acid = HC2H3O2 = CH3COOH • Hydrogen sulfide = H2S Dihydrogen phosphate ion = H2PO4- Monohydrogen phosphate ion = HPO42- Bicarbonate ion = HCO3-

  4. Bases Arrhenius bases • produce OH− ions (hydroxide ions) in water. • taste bitter or chalky. • are electrolytes. • feel soapy and slippery. • neutralize acids.

  5. Hydroxides are typical Arrhenius Bases

  6. BrØnsted-Lowry Acids and Bases According to the BrØnsted-Lowry theory, • acids donate a proton (H+). • bases accept a proton (H+).

  7. NH3, a BrØnsted-Lowry Base In the reaction of ammonia and water, • NH3 is the base that accept H+. • H2O is the acid that donates H+.

  8. NH3

  9. Comparing Acids and Bases Identify compound as acid or based by given property and formula.

  10. Learning Check Identify each as a characteristic of an A) acid or B) base. 1. has a sour taste 2. produces OH- in aqueous solutions 3. has a chalky taste 4. is an electrolyte 5. produces H+ in aqueous solutions

  11. Strengths of Acids and Bases

  12. Strong and Weak Acids • In an HCl solution, the strong acid HCl dissociates 100%. • A solution of the weak acid CH3COOH contains mostly molecules and a few ions.

  13. A strong acidcompletely ionizes (100%) in aqueous solutions. Is a strong electrolyte. HCl(g) + H2O(l) H3O+ (aq) + Cl− (aq)

  14. A weak acid dissociates only slightly in water to form a few ions in aqueous solutions. H2CO3(aq) + H2O(l) H3O+(aq) + HCO3− (aq)

  15. Strong Bases Strong bases • are formed from metals of Groups 1A (1) and 2A (2). • include LiOH, NaOH, KOH, and Ca(OH)2. • dissociate completely in water. KOH(s) K+(aq) + OH−(aq)

  16. Weak Bases Weak bases • are most other bases. • dissociate only slightly in water. • form only a few ions in water. NH3(g) + H2O(l) NH4+(aq) + OH−(aq)

  17. Ionization of Water H2O + H2O H3O++ OH-

  18. Pure Water is Neutral In pure water, • the ionization of water molecules produces small, but equal quantities of H3O+ and OH−ions. • molar concentrations are indicated in brackets as [H3O+] and [OH−]. [H3O+] = 1.0 x 10−7 M [OH−]=1.0 x 10−7 M

  19. Ion Product of Water, Kw The ion product constant, Kw, for water • is the product of the concentrations of the hydronium (H3O+ or H+ hydrogen ion) and hydroxide ions (OH-). Kw = [ H3O+][ OH−] • can be obtained from the concentrations in pure water. Kw = [ H3O+][ OH−] Kw = [1.0 x 10− 7 M] x [ 1.0 x 10− 7 M] = 1.0 x 10− 14

  20. Acidic Solutions Adding an acid to pure water • increases the [H3O+]. • cause the [H3O+] to exceed 1.0 x 10-7 M. • decreases the [OH−].

  21. Basic Solutions Adding a base to pure water • increases the [OH−]. • causes the [OH−] to exceed 1.0 x 10− 7M. • decreases the [H3O+].

  22. acidic – neutral – basic solutions

  23. [H3O+] determines acid or neutral or base 1.0 x 10-7M = 0.0000001 = neutral If < -7 (ie -1 through -6) = acidic If > -7 (ie -8 through -14) = basic

  24. Calculate [H3O+] or [OH-] Kw = 1.0×10-14 =[H3O+] x [OH- ] If [H3O+] is known: If [OH- ] is known:

  25. Calculating [H3O+] What is the [H3O+] of a solution if [OH−] is 5.0 x 10-8M? STEP 1: Write the Kw for water. Kw = [H3O+ ][OH−] = 1.0 x 10−14 STEP 2: Rearrange the Kw expression. STEP 3: Substitute [OH−]. 2.0 × 10-7 M

  26. Learning Check If lemon juice has [H3O+] of 2 x 10−3 M, what is the [OH−] of the solution? Rearrange the Kw to solve for [OH- ] Kw = [H3O+ ][OH−] = 1.0 x 10−14 5 x 10−12 M

  27. Learning Check The [OH−] of an ammonia solution is 4.0 x 10−2 M. What is the [H3O+ ] of the solution? 2.5 x 10−13 M

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