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Topic: Find PH of Solution  (Read 2738 times)

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Offline benworld128

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Find PH of Solution
« on: October 27, 2011, 12:26:35 AM »
Two acid are combined in solutions , first being .500M HF and second being .100M HNO3.

Ka HF = 3.5 X 10-4

Find PH.

How do I solve it ?

Not sure how to proceed with this problem.
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Offline benworld128

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Re: Find PH of Solution
« Reply #1 on: October 27, 2011, 12:31:35 AM »
Do I have to find PH for each one... since HNO3 is strong acid its ph is 1

And since HF is weak acid, after solving for ka and doing approximation method I get x = 1.75 E -4  , ph of that is 3.75

So I  would have two ph in  one solution ?
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Offline AWK

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Re: Find PH of Solution
« Reply #2 on: October 27, 2011, 02:29:21 AM »
Forget about a weak acid in the presence of the strong one.
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AWK

Offline Borek

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Re: Find PH of Solution
« Reply #3 on: October 27, 2011, 02:46:16 AM »
Quote from: benworld128 on October 27, 2011, 12:31:35 AM
So I  would have two ph in  one solution ?

No, you will have one pH in the solution, with both acids contributing to it. If acids have similar strengths, calculations can be difficult, but when they differ in strengths approach suggested by AWK will work.
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