Homework Help: chem

Posted by tomi on Thursday, April 16, 2009 at 2:09pm.

Calculate [H3O] in the following solutions.
5.15x10-2M HCl and 7.62x10-2M NaC2H3O2

Responses

HCl + NaC2H3O2. It appears there is an excess of H^+ which will react with NaC2H3O2 to form HC2H3O2. That gives you a buffer of C2H3O2 and HC2H3O2 and you use the H-H equation to solve for pH.
Post your work if you get stuck.

i used the H-H equation.
pKa=4.74, conjugate base= 7.62x10-2, Acid=5.15X10-2. i got a pH 0f 4.91 and H30 turned out to be 1.2X10-5.
Is this right?

chem - DrBob222, Thursday, April 16, 2009 at 3:04pm
I don't think so.
Now that I see the question again, I'm wondering if this is a problem with two parts; i.e., the question is asking for the pH of 0.0515 M HCl and for the pH of a separate solution of 0.0762 M NaC2H3O2? And after noticing that there is no volumes listed for EITHER solution, I suspect this may be the right interpretation. So the first would be the pH of HCl and the second would be the pH of a sodium acetate solution and my first response would be null and void.
IF, however, it really is a mixture of two solutions, I started with 100 mL of each. That gives me 5.15 mmoles HCl and 7.62 mmoles NaC2H3O2. The final product is 5.15 mmoles (which you have correctly identified) BUT the sodium acetate remaining is 7.62 mmoles - 5.15 mmoles = 2.47 mmoles.
pH = 4.74 + log(2.47/5.15) = 4.42. Check my work but especially look at the question again. I'll bet you are to determine the pH of EACH solution separately and it isn't a mixture.
chem - vanessa, Thursday, April 23, 2009 at 8:07pm
i'm problems with the same question, did you find out the correct answer?
and to clarify, the question is asking the [H30+] concentration when the 2 are mixed, so you have to use the common ion effect method.

Answer this Question

Related Questions

chemistry - Calculate [H3O] in the following solutions. a)4.0×10&#8722...
Chemistry - a solution is made by combining 5 mL of .2M HC2H3O2, 5 mL of .2M ...
Chemistry - Calculate the pH of 75 ml of the buffer composed of .1M HC2H3O2 with...
Chemistry - Hi please help with this. You will mix 5 ml of each 2M HCL and 2M ...
ap chemistry - for the following, mix the equal volumes of one solution from ...
CHEM - 0.16 M HC2H3O2 and 0.31 M of NAC2H3O2 titrated with what ml of 0.25 M HCL...
chem--buffers - Calculate [H30+] in a solution that is 0.0525M HCl and 0.768M ...
Chemistry - 1) How many drops of 12M HCl would you add to 1.00 L of 0.100 M ...
Chemistry - In each of the following groups, identify the two substances whose ...
Chemistry - What volume of 6M HCl and 2M HCl should be mixed to get 2 litres of ...

For Further Reading

First Name:
School Subject:
Answer: