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Topic: Calculating the pH of a solution.  (Read 5338 times)

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Offline Scoobiedoobiedoo!

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Calculating the pH of a solution.
« on: November 15, 2008, 10:24:30 AM »
25cm3 of 1 mol/dm-3 HCl mixed with 25cm3 of 0.5 mol dm-3 NaCl, find the ph of the solution.

Any help working these types of questions out would be great.
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Offline enahs

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Re: Calculating the pH of a solution.
« Reply #1 on: November 15, 2008, 10:36:10 AM »
Strong acid and Strong base react completley to neutralize each other. Which one is in excess? How much of the excess is left over? What is the pH of that?

Please show your attempts and try your problems. We spend our free time to help people, not do homework problems for them. If we were going to do peoples homework problems, I would be asking a fee!  :D
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Offline Scoobiedoobiedoo!

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Re: Calculating the pH of a solution.
« Reply #2 on: November 15, 2008, 10:39:18 AM »
Yeh sorry about lack of attempt, but thanks for help I had forgotten that one was in excess :)
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Offline enahs

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Re: Calculating the pH of a solution.
« Reply #3 on: November 15, 2008, 10:46:22 AM »
Wait!
I looked back again.
The first time I read it as "NaOH". But you typed "NaCl". If it is NaCl, a salt, it has no effect for your purposes and level. If it is NaOH as I originally thought (as it makes sense) then that method is correct.
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Offline Scoobiedoobiedoo!

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Re: Calculating the pH of a solution.
« Reply #4 on: November 15, 2008, 10:52:34 AM »
Not a typo I would assume it is meant to be in a solution. I am not in a high school in America by the way, these are questions found in an aptitude test for Cambridge uni. 
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Offline Borek

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Re: Calculating the pH of a solution.
« Reply #5 on: November 15, 2008, 11:09:40 AM »
Ionic strength 0.75. So it is either a typo or just a dilution problem.
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Offline Scoobiedoobiedoo!

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Re: Calculating the pH of a solution.
« Reply #6 on: November 15, 2008, 11:26:30 AM »
Well it was a question made by the top university in the world so I would go with a dilution problem, how much temperature aproximately do you think would be needed?
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Offline Borek

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Re: Calculating the pH of a solution.
« Reply #7 on: November 15, 2008, 11:31:46 AM »
Quote from: ConcH2SO4+Water!!! on November 15, 2008, 11:26:30 AM
how much temperature aproximately do you think would be needed?

Huh? You sure Cambridge won't be too demanding?  ;)
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Offline Scoobiedoobiedoo!

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Re: Calculating the pH of a solution.
« Reply #8 on: November 15, 2008, 11:33:38 AM »
I am not doing chemistry lol I am doing Biology but we need a base knowledge of certain aspects of chemistry.
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Offline AWK

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Re: Calculating the pH of a solution.
« Reply #9 on: November 17, 2008, 01:08:05 AM »
After dilution this is 0.5 M HCl with an ionic strength of 0.75 M.
pH calculated on the basis of H3O+ concentration should be corrected by about +0.14 taking into account the ionic strength.
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Offline Scoobiedoobiedoo!

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Re: Calculating the pH of a solution.
« Reply #10 on: November 17, 2008, 03:28:03 PM »
I get ph 3.2 of the mixture from the .000625 mol/dm-3 excess HCl after the reaction. Was I right in doing -log0.000625 ?


Thanks again for all your help.
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Offline Borek

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Re: Calculating the pH of a solution.
« Reply #11 on: November 17, 2008, 05:58:05 PM »
Doesn't look OK to me.

How many moles of HCl were left after reaction?

What was solution volume?

What was concentration of HCl left?
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