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Acids and Bases

Acids and Bases. These are acids…. HNO 3 HCl H 2 SO 4 HC 2 H 2 OOH H 3 PO 4 What do they all have in common?. What all acids have in common…. Sour or tart taste (take my word for it) Electrolytes in solution React with metals to produce H 2(g)

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Acids and Bases

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  1. Acids and Bases

  2. These are acids….. • HNO3 • HCl • H2SO4 • HC2H2OOH • H3PO4 • What do they all have in common?

  3. What all acids have in common… • Sour or tart taste (take my word for it) • Electrolytes in solution • React with metals to produce H2(g) • React with bases to produce water and a salt • Change the color of an acid/base indicator • Many are in foods and drinks.

  4. These are all bases…. • NaOH • KOH • Ca(OH)2 • Mg(OH)2 • What do they all have in common? • NH3 is also a base.

  5. What all bases have in common… • Taste bitter (take my word for it) • Feel slippery on skin (take my word for it) • Electrolytes in solution • Change the color of an acid/base indicator • React with acids to produce water and a salt • Almost none are in foods.

  6. Arrhenius Acids and Bases • Acids ionize in water to produce hydrogen ions (H+) • HCl + H2O → H+(aq) + Cl-(aq) • Bases ionize in water to produce hydroxide ions (OH-) • NaOH + H2O → Na+(aq) + OH-(aq)

  7. Brönsted-Lowry Acids and Bases • An acid donates a hydrogen ion (H+) • HCl + H2O → H+(aq) + Cl-(aq) • A base accepts a hydrogen ion • NH3(g) + H2O(l) → NH4+(aq) + OH-(aq) • That’s why NH3 is listed as a base!

  8. Conjugate Acids and Bases • HCl + H2O → H+(aq) + Cl-(aq) • A more accurate version is this: • HCl + H2O ↔ H3O+ + Cl- • H3O+ is called hydronium ion • We are agreed that reactions are reversible, right?

  9. Self-Ionization of Water • Sometimes water comes apart: • H2O ↔ H+(aq) + OH-(aq) • If [H+] = [OH-] you have a neutral solution • In H2O, [H+] = 1.0 x 10-7M. So is [OH-] • For any aqueous solution, [H+] x [OH-] = 1 x 10-14 • This is called the ion-product constant for water, Kw = [H+] x [OH-] =1.0 x 10-14

  10. Self-Ionization of Water • In an acidic solution, [H+] > [OH-] • In an acidic solution, [H+] > 1.0 x 10-7M • In a basic solution, [OH-] > [H+] • In a basic solution, [H+] < 1.0 x 10-7M • pH = -log[H+]

  11. pH • pH = -log[H+] • In a neutral solution, [H+] = 1.0 x 10-7M • What is the pH? • If [H+] = 4.8 x 10-8M, what is the pH? • If pH = 3.32, what is [H+]? • [H+] = antilog(-pH)

  12. Titration • Method of determining the concentration of an acid/base. • Let’s say you have an acid of unknown concentration. • You add a base, whose concentration is known, until an indicator shows that you are at the equivalence point. • Equivalence point is where moles of acid=moles of base.

  13. Titration • At the equivalence point, MaVa=MbVb • During the actual titration, it is HUGELY important that you do not overrun the equivalence point. • Example: 40.0mL of a nitric acid solution required 32.6mL of 0.50M NaOH to neutralize it. What is the molarity of the nitric acid?

  14. Strong/Weak Acids & Bases

  15. Strong/Weak Acids & Bases • What do acids do in water? • They IONIZE • Some ionize completely (strong), and some hardly ionize at all (weak). • Strong acids: HCl, H2SO4, HNO3, H3PO4, H2CO3, HClO,CH3COOH

  16. Strong/Weak Acids & Bases • Ka, the acid dissociation constant, is a ratio that numerically expresses how strong an acid is. • Strong acids have a high Ka value (1 or higher), and weak acids have a low Ka value (far below 1).

  17. Salt Hydrolysis Rxns • When salts dissolve in water, they dissociate into their component ions. • Some of these ions act as weak Bronsted-Lowry acids or bases. • There are four possibilities….

  18. Salts of Strong Acids and Bases—(NaCl, K2SO4) produce neutral solutions • Salts of Strong Acids & Weak Bases– (NH4Cl) produce slightly acidic solutions

  19. 3. Salts of Weak Acids & Strong Bases—(Na2CO3)produce slightly basic solutions. 4. Salts of Weak Acids and Bases— can produce either acidic, basic, or neutral solutions. Very hard to predict

  20. Strong Acids • H2SO4—Sulfuric • HNO3—Nitric • All of the hydrogen halides except fluorine (HCl—Hydrochloric, HBr—Hydrobromic, HI—Hydroiodic)

  21. Strong Bases • All of the hydroxides of the alkali metals (LiOH, NaOH, KOH, RbOH, CsOH) • The hydroxides of the alkaline earth metals except for Be and Mg (Ca(OH)2, Sr(OH)2, Ba(OH)2)

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