Question 6E.3 7th edition

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ConnorRazmaDis2I
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Question 6E.3 7th edition

Postby ConnorRazmaDis2I » Sun Jan 20, 2019 10:28 pm

The question states "ignoring second deprotonations only when the approximation is justified. How do we know when its justified?

aisteles1G
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Re: Question 6E.3 7th edition

Postby aisteles1G » Mon Jan 21, 2019 2:10 pm

When the difference in Ka1 and Ka2 values is over 10^3 you can ignore the second Ka and just use the one for ka1 but if its like ka1= 1*10^-2 and ka2=1*10^-3 then you have to use the second K value and can't ignore it. Hope this helps! It talks about this in the 6E chapter in the textbook

Chem_Mod
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Re: Question 6E.3 7th edition

Postby Chem_Mod » Mon Jan 21, 2019 2:12 pm

The book states that the second deprotonation will always occur, but so long as the provided Ka2 is less than about Ka1/1000 then the second deprotonation will be so small that it will not affect the pH significantly and can thus be ignored.


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