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Chapter 16 Acids and Bases

Chemistry B2A. Chapter 16 Acids and Bases. Acids and Bases. Acids: sour. Bases: bitter or salty. Acids and Bases. Arrhenius definition:. (If H 2 O is involved.). Acid: produces H 3 O +. CH 3 COOH(aq) + H 2 O(l) CH 3 COO - (aq) + H 3 O + (aq). H 3 O + (Hydronium ion):.

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Chapter 16 Acids and Bases

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  1. Chemistry B2A Chapter 16 Acids and Bases

  2. Acids and Bases Acids: sour Bases: bitter or salty

  3. Acids and Bases Arrhenius definition: (If H2O is involved.) Acid: produces H3O+ CH3COOH(aq) + H2O(l) CH3COO-(aq) + H3O+(aq) H3O+ (Hydronium ion): H+(aq) + H2O(l) H3O+(aq) Base: produces OH- H2O NaOH(s) Na+(aq) + OH-(aq) NH3(aq) + H2O(l) NH4+(aq) + OH-(aq)

  4. Acids and Bases Bronsted and Lowry definition: (If H2O is not involved.) Acid: donates H+ (proton) Base: accepts H+ (proton) HCl + H2O Cl- + H3O+ acid base Conjugate base Conjugate acid Conjugate acid-base pair Conjugate acid-base pair

  5. Acids and Bases HCl + H2O Cl- + H3O+ Proton (H+) is transferred.

  6. CH3COOH + NH3 CH3COO- + NH4+ acid base Conjugate base Conjugate acid Conjugate acid-base pair Conjugate acid-base pair Acids and Bases C6H5OH + H2O C6H5O- + H3O+ acid base Conjugate base Conjugate acid Conjugate acid-base pair Conjugate acid-base pair

  7. Acids and Bases Weak acid and base:is partially ionized in aqueous solution. produces less H+ and OH- CH3COOH(aq) + H2O(l) CH3COO-(aq) + H3O+(aq) NH3(aq) + H2O(l) NH4+(aq) + OH-(aq) Strong acid and base:is completely ionized in aqueous solution. produces more H+ and OH- HCl(aq) + H2O(l) Cl-(aq) + H3O+(aq) NaOH(aq) + H2O(l) Na+(aq) + OH-(aq)

  8. Acids and Bases HCl(aq) + H2O(l) Cl-(aq) + H3O+(aq)

  9. Acids and Bases A strong acid contains a weak conjugate base.

  10. Amphiprotic:it can act as either an acid or a base. HCl(aq) + H2O(l) Cl-(aq) + H3O+(aq) base NaOH(aq) + H2O(l) Na+(aq) + OH-(aq) acid Acids and Bases Monoprotic acids HCl Triprotic acids H3PO4 Diprotic acids H2SO4

  11. Acids and Bases Oxyacids: acidic H is attached to an oxygen atom. H2SO4 H3PO4 HNO3 Organic acids: contain carboxyl group (-COOH). They are usually weak. CH3COOH

  12. Anion : -ide ion + Hydro -ic acid Naming binary acids HF F-: flouride ion Hydroflouric acid HCl Cl-: chloride ion Hydrochloric acid H2S S2-: sulfuride ion Hydrosulfuric acid

  13. Naming ternary acids -ite ion -ous acid Anion: -ate ion -ic acid HNO2 NO2-: Nitrite ion Nitrous acid HNO3 NO3-: Nitrate ion Nitric acid H2CO3 CO32-: carbonate ion carbonic acid H2SO3 SO32-: sulfurite ion sulfurous acid

  14. [A-] [H3O+] Ka < 1 Ka = K [H2O] = Acid ionization constant [HA] Ka↑ or pKa ↓ Stronger acid Ionization constant HA + H2O A- + H3O+ [A-] [H3O+] K = not for strong acids Equilibrium constant [HA] [H2O] - Log Ka = pKa

  15. Ionization of water H2O + H2O OH- + H3O+ KW = [H3O+] [OH-] = (1×10-7) (1×10-7) [H3O+] [OH-] = 1×10-14 pH + pOH = 14

  16. [H+] and [OH-] [H+] = [OH-] Neutral solution [H+] > [OH-] Acidic solution [H+] < [OH-] Basic solution

  17. pH and pOH pH = - log [H3O+] or -log [H+] pOH = - log [OH-] pH scale: 0 7 14 Base Neutral Acid [H3O+] ↑ [H3O+] ↓ and [OH-] ↑

  18. pH meter and pH indicators

  19. Nature & pH indicators Bigleaf Hydrangea In acidic soil In basic soil (alkaline)

  20. pH of strong acids HCl(aq) + H2O(l) Cl-(aq) + H3O+(aq) 0.10 M HCl  pH = ? 0.10 M HCl  0.10 M H+ and 0.10 M Cl- [H+] = 0.10 M pH = -log [H+] pH = -log (0.10) = 1.00

  21. 2. Reaction with metal hydroxides: a salt and water are produced. KOH(aq) + 2HCl(aq) KCl(aq) + H2O(l) Acid Reactions 1. Reaction with metals (strong acids): a salt and H2 are produced. Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g)

  22. Acid Reactions 3. Neutralization: reaction between an acid and a base. A salt and water are produced. KOH(aq) + 2HCl(aq) KCl(aq) + H2O(l) 2NaOH(aq) + H2SO4(aq) Na2SO4(aq) + 2H2O(l) Strong acid reacts with strong base to produce the weaker acid and weaker base. (This is the direction of a reaction)

  23. B A Titration (Neutralization reaction) MB: known VB: known MA: unknown VA: known Equivalence point: equal amount of acid (H+) and base (OH-) (pH = 7). NaOH + HNO3 NaNO3 + H2O MA× VA = MB× VB

  24. Normality 2NaOH + 1H2SO4 NaSO4 + 2H2O Different coefficients Equivalent of an acid = amount of an acid that can furnish 1 mol of H+ Equivalent of a base = amount of a base that can furnish 1 mol of OH- Equivalent weight of acid (base) = mass (g) of 1 equivalent of that acid (base). HCl 1 equivalent HCl = 1 mole HCl equivalent weight HCl = 36.5 g NaOH 1 equivalent NaOH = 1 mol NaOH equivalent weight NaOH = 40 g

  25. Normality H2SO4 1 mol H2SO4 = 2 mol H+ 1/2 mol H2SO4 = 1 mol H+ 1 equivalent H2SO4 = 1/2 mole H2SO4 equivalent weight H2SO4 = 98.0/2 = 49.0 g H3PO3 1 mol H3PO3 = 3 mol H+ 1/3 mol H3PO3 = 1 mol H+ 1 equivalent H3PO3 = 1/3 mole H3PO3 equivalent weight H3PO3 = 82.0/3 = 27.3 g

  26. Normality Number of equivalents Normality = Volume of solution (L) NAVA = the number of equivalents of an acid NBVB = the number of equivalents of a base [H+] = [OH-] Neutralization: number of equivalents of an acid = number of equivalents of a base NA× VA = NB× VB

  27. Buffers acid or base pH stays constant. Buffer Equal molar amount of a weak acid and a salt of weak acid. Equal molar amount of a weak acid and its conjugate base. 1 mole CH3COOH + 1 mole CH3COONa 1 mole CH3COOH + 1 mole CH3COO-

  28. Buffers pH of blood = between 7.35 and 7.45 Carbonate buffer H2CO3 / HCO3- Phosphate buffer H2PO4- / HPO42- Proteins buffer H2CO3 + OH-→ HCO3- + H2O HCO3- + H3O+ → H2CO3 + H2O

  29. HA + H2O A- + H3O+ If [AH] (weak acid) ≠ [A-] (conjugate base) Henderson-Hasselbalch equation: [A-] pH = pKa + log [HA] Buffers If [AH] (weak acid) = [A-] (conjugate base) pH of buffer = pKa of weak acid

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