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Acids - Bases

Acids - Bases. Arrhenius : Acid …. A substance that increases the hydrogen ion, H + , concentration when dissolved in H 2 O. Eg. HCl, H 2 SO 4 , HC 2 H 3 O 2 (CH 3 COOH), etc. Base…. A substance that increases hydroxide ion, OH - , concentration. Eg. NaOH, NH 4 OH, etc.

bernard-casey
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Acids - Bases

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  1. Acids-Bases Arrhenius: Acid…. A substance that increases the hydrogen ion, H+, concentration when dissolved in H2O. Eg. HCl, H2SO4, HC2H3O2 (CH3COOH), etc. Base…. A substance that increases hydroxide ion, OH-, concentration. Eg. NaOH, NH4OH, etc. Bronsted-Lowry (1923) (not worried about increasing/decreasing H+ or OH- concentrations) Acid … a “proton donor”, p+ = H+, any formula HA. Eg. HCl, H2SO4, HC2H3O2 (CH3COOH), etc. Base …. A “proton acceptor” Eg. OH-,NH3 ; Cl-

  2. Acid solutions: HCl(g) + H2O(l) H3O+(aq) + Cl-(aq) .. H .. + .. .. H :Cl: H :O: - + .. .. H :O: + :Cl: .. .. H H Hydrogen ion, H+, or hydronium ion, H3O+ has formed H3O+(aq) = H+(aq) HCl(g) + H2O(l)H+(aq)+ Cl-(aq)

  3. Strengthof an acid can be determined by conductivity. Good or poor electrolyte? Large or small # of ions? 12 M HCl HCl(g) + H2O(l)H3O+(aq)+ Cl-(aq)

  4. Strengthof an acid can be determined by conductivity. Good or poorelectrolyte? Large or small # of ions? Pure HC2H3O2 Diluted HC2H3O2

  5. Properties of Acids:

  6. More Bronsted-Lowry Acid/Base info: General acid/base reaction: HA + B = A- + HB+

  7. Titration problems What is the volume of a 0.325 M NaOH solution needed to just neutralize 65.2 ml of 1.37 M HNO3? Balanced equation: 1 NaOH + 1 HNO3 = 1 HOH + 1NaNO3 65.2ml x x x x x = 274.8 = 275ml NaOH

  8. Basic Solutions: • Strong Arrhenius bases: • Group IA hydroxides. Eg. NaOH, KOH • Lower Group IIA hydroxides. Eg. Sr(OH)2, Ba(OH)2

  9. More Bronsted-Lowry Acid/Base info: Bases react with water to produce OH-

  10. Acidic solution Neutral solution Basic solution Hydrolysis Salt + H2O 

  11. Hydrolysis (continue) NaClO + H2O : NaClO is a salt of a base NaOH and an acid HClO

  12. Lewis Acid/Base Lewis acid: electron pair acceptor Lewis base: electron pair donor + H H .. .. H+ + :N: H .. : N : H H .. H H “adduct” … the product of a L.acid/base rxn

  13. Acid-Base Equilibria Review: In pure water & all aqueous solutions: H2O + H2O = H3O++OH-

  14. Solutions of Strong Acids/ Bases: 0.10 M HNO3 actually consists of 0.10 M H3O+ or [H+] = 0.10 M 0.10 M NaOH…. Adds 0.10 OH- to the water solution

  15. Solutions of Weak acids/bases 0.10 MHC2H3O2: a weak acid - when it reacts with water it does not ionize100%. What is the[H3O+]forthis solution? Ka = 1.8 x 10-5

  16. Weak acids (continue) [H3O+] [C2H3O2-] Ka = = 1.8 x 10-5 [HC2H3O2] [H3O+] = [C2H3O2-] = [HC2H3O2 ] =

  17. Weak acids (continue) So…. 2 = 1.8 x 10-5

  18. Weak bases…. B + H2O = BH+ + OH- NH3 + H2O =

  19. Weak bases (continue) If the [OH-] = 2.5 x 10 -3 , what is the [H3O+]?

  20. pH A simple scale for ranking the H3O+ concentrations of dilute acid/base solutions. (Sorenson). The logarithm of a number is that number expressed as an exponent of the base 10. For example, the logarithm of 1 is 0, 1 x 100.

  21. pH Scale [H3O+][OH-]= 1x10-14 pH = - log[H3O] pH + pOH = 14 Formulas to remember

  22. More About the pH Scale • Given a 3.25 x 10-4 M HNO3 , solve for: • [H3O+] • pH = • [OH-] =

  23. Sample Problem What is the pH of a 0.10 M HC2H3O2 solution? [H3O+] [C2H3O2-] = 1.8 x 10-5 Ka = [HC2H3O2 ]

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