19 Acid & Base Ionization Constants

19 Acid & Base Ionization Constants - Which one of the...

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1 1 Which one of the following is not correct? If all are correct, respond (E) A) A reaction as written (I+II III+IV) has both a forward direction and a reverse direction. B) A reaction has both an exothermic direction and an endothermic direction. I+II III+IV with H<0 is exothermic. III+IV I+II with H>0 is endothermic. C) When the temperature decreases, equilibrium shifts toward the exothermic direction. D) When the temperature increases, equilibrium shifts toward the endothermic direction. E) A – D all are correct statements. 1 ln( ) oo H S K RT R  2 How good is enzyme catalysis for the production of ammonia? Compare the equilibrium constants at 300 K and 800 K (used in the commercial process). N 2 (g) + 3H 2 (g) 2NH 3 (g): H o = - 92 kJ/mol, S o = - 199 J/mol K, G o = - 32 kJ/mol R = 8.314 J/mol K What did you get? A) 300 K = 4.2 x 10 5 and 800 K = 4.1 x 10 -5 B) 36.9 and 23.9 C) 12 x 10 3 and 8 x 10 -3 D) 13.0 and 10.1 o ln( ) G=H-TS 1 o G K RT H S K R TR 
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2 3 Acid Ionization Equilibrium Constants HA + H 2 O H 3 0 + + A - If K a >> 1 Ionization is essentially 100% Called strong acids K a <1 Only a fraction of the molecules ionize. Called weak acids See values in MSJ Table 16.2. p. 788 K a = [H 3 O + ] [A - ] [HA] 4 Weak Acid Example Weak acids do not ionize completely in water. Equilibrium is reached before the acid has ionized completely into ions. HF(aq) + H 2 O(l) H 3 O + (aq) + F - (aq) Lots of this! Not much of this! K a = [H 3 O + ] [F - ] [HF] < 1 Acid Conjugate Base
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3 5 Base Ionization Equilibrium Constants B + H 2 O BH + + 0H - If K b >> 1 Ionization is essentially 100% Called strong bases K b <1 Only a fraction of the molecules ionize.
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This note was uploaded on 02/13/2011 for the course CHE 132 taught by Professor Hanson during the Spring '08 term at SUNY Stony Brook.

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19 Acid & Base Ionization Constants - Which one of the...

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