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STRONG BASES LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH) 2 , Sr(OH) 2 , Ba(OH) 2

STRONG BASES LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH) 2 , Sr(OH) 2 , Ba(OH) 2. Equations for Strong Arrhenius bases - ionize completely to form OH - LiOH (s) → Li + + OH - Ca(OH) 2 (s) → Ca 2+ + 2 OH -. Calculate the pH of 0.15M Calcium hydroxide solution.

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STRONG BASES LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH) 2 , Sr(OH) 2 , Ba(OH) 2

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  1. STRONG BASES • LiOH, NaOH, KOH, RbOH, CsOH, • Ca(OH)2, Sr(OH)2, Ba(OH)2 Equations for Strong Arrhenius bases - ionize completely to form OH- LiOH (s) → Li+ + OH - Ca(OH)2 (s) → Ca2+ + 2 OH - Calculate the pH of 0.15M Calcium hydroxide solution.

  2. Weak Acids & Bases Equations for dissociation ( produce OH- by equilibrium dissociation) 1. Weak OH- bases Fe(OH)3(s) Fe 3+(aq) + 3 OH-(aq) 2. Weak NH3 bases NH3 (aq) NH4+(aq) + OH-(aq) 3. Conjugate of weak acid-bases: OCl-(aq) HOCl (aq) + OH- (aq) Base Dissociation Constant: Kb Kb = [NH4+] [OH-] NH3(aq) + H2O ↔OH- (aq) + NH4+ (aq) [NH3]

  3. Write the dissociation equation and the Kb expression for the reaction of each base with water: • Propyl amine, C3H7NH2 • Monohydrogen phosphate ion, HPO42- • Benzoate ion, C6H5CO2- • Calculate the molar concentration of OH-ions in a 1.15M solution of hypo bromite ion, BrO-, Kb = 4.0 x 10-6. What is the pH?

  4. Weak Base Problem solving with % Ionization Weak Base Problem #2 Ammonia is a weak base that dissociates in water with a dissociation constant, Kb = 1.8 x 10-5 : NH3 + H2O  NH4+ + OH- I C E • Determine the hydroxide ion concentration and the % dissociation of 0.150M solution of ammonia. • Determine the pH of a solution prepared by adding 0.0500 mole of solid ammonium chloride to 100 ml of 0.15M ammonia.

  5. I. Arrhenius Acids form H3O+, Bases form OH- HCl H3O + + Cl- Ca(OH)2 Ca2+ + 2 OH- • Bronsted-Lowry Acids donate protons Bases accept protons HF + OH- F- + H2ONH3 + H2O  NH4+ + OH- • Lewis Acids are electron pairBases are electron pair acceptors donors Zn2+ (aq) + 4H2O : Zn(H2O)42+ (aq) acidbase

  6. Identifying Acids & Bases • Write the formula, identify as • Arrehnius, B-L, Lewis • Acid or Base • Write the conjugate partner: • Write the acid equation: • Write the base equation:

  7. Chalkboard Races Write the following net ionic equations, guess the pH when 1 M solutions are mixed. NH3 C6H5COOH NaOH + HNO3 NaOH + CH3COOH Mg(OH)2 H3PO4 HCl + KOH HCl + NH3

  8. Writing Net Ionic Acid-Base Reactions • 1. Strong acid - strong base: • net: H+(aq) + OH-(aq)  H2O • 2. Strong base - weak acid (HF + Ca(OH)2 ) • net: HF(aq) + OH- H2O + F-(aq) • 3. Strong acid - weak base ( HCl + NH3 ) • net: H+(aq) + NH3(aq)  NH4+(aq) • *In each case, the species present at highest concentrationis written • * Weak or insoluble are written as molecular, • strong or soluble are written as ions. • Notice that salts of weak acids will form basic solutions, • and salts of weak bases will form acidic solutions.

  9. Polyprotic Acids Polyprotic Acids When acid has more than one hydrogen proton, it will have more than one Ka. Ka1 = the dissociation constant for the first proton, will be much larger Ka2 = second dissociation constant, much lower than the first. Example: H2S  H+ + HS- HS-  H+ + S-2 The total Ka for a polyprotic acid is Ka1 x Ka2 = [H+][HS-] [H+][S2-] [H2S] [HS-] which results in an overall Ka= [H+]2 [S2-] [H2S] Ka1 = [H+][HS-] Ka1 = [H2S] Ka2 = [H+][S2-] Ka2 = [HS-]

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