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Topic: Buffer questions please help  (Read 8084 times)

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Offline jokulsa

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Re: Buffer questions please help
« Reply #15 on: October 06, 2014, 04:00:54 AM »
ok so is it

pH = pKa + log([base]/[acid])

3.50 = 3.14 + log([0.15]/[acid])

...and then finding [acid]?
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Offline Hunter2

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Re: Buffer questions please help
« Reply #16 on: October 06, 2014, 04:14:07 AM »
Yes correct. Solve the equation to Acid.
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Offline jokulsa

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Re: Buffer questions please help
« Reply #17 on: October 06, 2014, 04:50:34 AM »
I solved it and got 0.065M HF.

I used mol=M×vol to find the moles of acid
= 0.0325

Is this correct?

However, I still don't understand why I had to calculate the moles of the base, when the [base] of 0.30M was given in the question.
Would you be able to explain this please?
thanks 
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Offline Hunter2

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Re: Buffer questions please help
« Reply #18 on: October 06, 2014, 05:33:54 AM »
The 0.065 mol is the result its not M. You convertet also the 0.3 M NaF to 0.15 mol

It was asks how much moles you have to add to 0.5 l. So for this reason you have to convert everything to the given volume.
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