Using the HH Equation

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tchar96_1F
Posts: 14
Joined: Fri Sep 26, 2014 2:02 pm

Using the HH Equation

Postby tchar96_1F » Tue Dec 09, 2014 2:05 am

For number 12.9 part a in the book, I don't understand why we can't use the HH equation, and we have to set up the ICE table?

The question says "Calculate the pH of the solution that results from mixing a) 30 mL of 0.05 M HCN with 70 mL of 0.03 M NaCN"

Thank you!

HimaniMadnawat3L
Posts: 15
Joined: Fri Sep 26, 2014 2:02 pm

Re: Using the HH Equation

Postby HimaniMadnawat3L » Tue Dec 09, 2014 3:53 pm

You can use the HH equation and still get the same answer. I did this and it worked out. If you notice, the problem says the +/-x values in the expression of Ka are deemed negligible and can be removed. This is basically the Henderson equation which you are left with since you are multiplying the Ka with the ratio of the Acid/Base, and this will give the hydronium concentration. This can give the pH.


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