chemexam3 - 17.1-17.8 - Bronsted-Lowry acid proton (H+)...

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17.1-17.8 - Bronsted-Lowry acid – proton (H+) donor - monoprotic – capable of donating one proton - polyprotic - capable of donating 2+ protons - Bronsted-Lowry base – proton acceptor - polyprotic bases – capable of accepting 2+ protons - conjugate acid-base pair – two species that differ from each other by the presence of one hydrogen ion - every rxn b/n a Bronsted acid/base involves two conjugate acid-base pairs - autoionization – water still conduts electricity to a small extent: 2H 2 O  H 3 O + + OH - - K w = [H 3 O + ] [OH - ] = 1.0 x 10 -14 - in a neutral solution, [H 3 O + ] = [OH - ], both are equal to 1.0 x 10 -7 - in an acidic solution, [H 3 O + ] > [OH - ], [H 3 O + ]>1.0 x 10 -7 - in a basic solution, [H 3 O + ] < [OH - ], [H 3 O + ] < 1.0x10 -7 - lower pH, greater [H + ], stronger acid, more of the acid ionizes - weak/strong acids/bases - strong monoprotic acid, [H 3 O + ] in solution = [original acid] (same for bases) - weak acid, [H 3 O + ] << [original acid] (same for bases) - for a series of weak monoprotic acids (type HA) of the same concentration, [H 3 O + ] will increase (pH decrease) as acids become stronger - for a series of weak bases, [OH - ] will increase (pH increase) as bases become stronger - K a = [H 3 O + ][A - ]/[HA] - equilibrium constants rules - large K, product favored; small K, reactant favored - strongest acids have largest K a values - strongest bases have largest K b values - the weaker the acid (smaller K a ), the stronger its conjugate base (larger K b ) - acid-base properties of common cations/anions - anions that are conjugate bases of strong acids are such weak bases that they have no effect on solution pH - there are numerous basic anions – all are conjugate bases of weak acids - basic cations are conjugate bases of acidic cations - all metal cations are hydrated in water - table 17.4 pg 774 - pK a = -logK a - pK a value decreases as acid strength increases - K a x K b = K w - all proton transfer rxns proceed from stronger acid and base to weaker acid and base - table 17.5 pg 778 - strong acid/base net ionic equation: H 3 O + + OH -  2 H 2 O - mixing equal amts of strong base with strong acid produces neutral solution (pH=7) - weak acid with strong base: equal amts produces a salt whose anion is the conjugate base of the weak acid, solution is basic - strong acid with weak base: equal amts produces a salt whose cation is conjugate acid of the weak base, solution is acidic - weak acid with weak base: equal amts produces a salt whose cation is conjugate acid of weak base and whose anion is conjugate base of weak acid, solution pH depends on K a /K b - approximation that [HA] equilibrium = [HA] – [H 3 O + ] is about [HA] 0 is valid whenever [HA] 0 is greater than or equal to 100xK a - example 17.8 pg 786 - polyprotic acids/bases: the pH of many polyprotic acids depends primarily on the H + generated in the first ionization step (same for bases) 19.2, 19.4-19.7 - in a spontaneous process, energy goes from being more concentrated to more disperse - second law of thermo: a spontaneous process is one that results in an increase of the entropy of the universe
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chemexam3 - 17.1-17.8 - Bronsted-Lowry acid proton (H+)...

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