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Topic: Acids and the Equilibrium Constant  (Read 6795 times)

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Offline Sis290025

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Acids and the Equilibrium Constant
« on: February 10, 2006, 03:43:14 PM »
Acids donate protons to water according to the general equation:

HA (aq) + H20 (l) <-> H30+ (aq) + A- (aq)

Consider the following acids and their equilibrium constants for reaction with water at 25C. If all the acids have the same initial concentration, which is the strongest acid (i.e. which donates the most protons to water)?

  a. HBrO, Kc = 2.0 x 10-9    
  b. HNO2, Kc = 4.5 x 10-4    
  c. HF, Kc = 3.5 x 10-4    
  d. HIO3, Kc = 1.7 x 10-1    


I am unsure what to do here, but, after complying equations of each in reference to the given general equation and forming the ratio of concentrations for each K_c, the higher the K_c indicates a higher proton number??? So is it HIO3??

Please explain. Thanks.

Offline Borek

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Re:Acids and the Equilibrium Constant
« Reply #1 on: February 10, 2006, 04:14:05 PM »
So is it HIO3??

Yes. The stronger the acid, the higher dissociation constant (and these Kc values are nothing else but Ka - acid dissociation constants - see acid base equilibrium and Bronsted-Lowry theory). HIO3 has the highest dissociation constant of these four acids, thus it is the strongest.
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