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Topic: need help with ph problems!!  (Read 1318 times)

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Offline asigna

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need help with ph problems!!
« on: February 26, 2013, 12:03:24 AM »
What is the pH of a 0.25 M methylamine solution?

The formula is ch3nh2
so what I did was .25*2=.5
-log(.5)=.30

Calculate the pH of a 0.50 M solution of potassium cyanide

the formula is kcn
I did -log(.5)=.30



Am I doing this right? I feel that since these aren't strong acids/bases there should be more work involved

Offline argulor

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Re: need help with ph problems!!
« Reply #1 on: February 26, 2013, 12:17:20 AM »
Am I doing this right? I feel that since these aren't strong acids/bases there should be more work involved

I agree. Are you familiar with ICE tables?

The pKb of methylamine is 3.36 and the pKb of KCN is 3.00.

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