Notes Auto Ionization of Water

Dissociation constants for a generalized acid

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Unformatted text preview: ion Constants: -for a generalized acid dissociation, HA(aq) + H2)(l) produces A-(aq) + H3O (aq) -the equilibrium expression would be: Kc=[H3O+][A-]/[HA] -this equilibrium constant is called the acid-dissociation constant, Ka -if see OH on product side, you will write a Kb -the greater the value of Ka, the stronger the acid -we only use Ka for weak acids, bc strong acid would have 0 in denominator -at 25 degrees Celsius: a description bc Ka is affected by temperature -what side of equilibrium are weak acids favoring: the left (reactants) -Ka is less than one ! Calculating Ka from pH: -the pH of a 0.10 M solution of formic acid, HCOOH, at 25 degrees celcius is 2.38. Calculate Ka for formic acid at this temperature -look at notebook ! Calculating Percent Ionization: -test you can do to see if assumption of initial concentration minus x can be made -if 5% bigger, have to apply .10-x, and have a quadratic -depends on strength of weak acid -look at notebook ! Polyprotic acid...
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