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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: mandy9008 on March 13, 2009, 04:32:49 PM

Title: determining Kb with given concentration and pH
Post by: mandy9008 on March 13, 2009, 04:32:49 PM

what is the Kb value for the base?

given:
0.120M weak base
pH=11.28

initially i thought about the equation
pH=pKa+log[base]
                [acid]

so i did:
11.28=pKa+log(0.120)
pKa=12.20

pKa=-log Ka
10^-12.20
Ka=6.31*10^-13

Ka*Kb=Kw=1.0*10^-14
Kb=.0158

this is not the answer, however.
please help me determine the answer

Title: Re: determining Kb with given concentration and pH
Post by: Borek on March 13, 2009, 05:25:24 PM

How would you calculate pH of the base knowing its concentration and Kb?