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Q: Calculation of Acid Constant ( Answered 5 out of 5 stars,   0 Comments )
Subject: Calculation of Acid Constant
Category: Science > Chemistry
Asked by: medicine_man-ga
List Price: $9.00
Posted: 19 Nov 2006 22:30 PST
Expires: 19 Dec 2006 22:30 PST
Question ID: 784170
The pH of a 0.55 mol L-1 solution of a weak acid, HZ, is 3.76.

Calculate Ka for HZ?

Please show workings.

Subject: Re: Calculation of Acid Constant
Answered By: livioflores-ga on 27 Nov 2006 22:07 PST
Rated:5 out of 5 stars

Assuming that the dissociation equation is:
HZ(aq) <---> H+ + Z- (aq)

Ka = [H+]^2/[HZ]   ([H+] = [Z-])

[H+] = 10^(-pH) = 10^(-3.76) = 1.7378*10^-4

Ka = (1.7378*10^-4)^2/0.55 = 5.491*10^-8

At the following Powerpoint file you will find an excellent source for
a further reading and explanations on this topic:
"Acids and Bases" by Tsun-Mei Chang at University of Wisconsin-Parkside site:

I hope this helps you. Feel free to request for a clarification if you need it.

Best regards,
medicine_man-ga rated this answer:5 out of 5 stars
Excellent answer thanks for your help :)

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