Posted by Saira on Thursday, July 9, 2009 at 2:01am.
[CH3COOH] + [CH3COO-]= 0.100 M
pH = pKa + log [CH3COO-] / [CH3COOH]
5.00 = 4.760 + log [CH3COO-] / [CH3COOH]
10^0.24 =1.74 = [CH3COO-]/ [CH3COOH]
I have an idea how to solve it but i dunt know how to get the M of CH3COO AND CH3COOH
So far so good. To save time in typing, I'll call CH3COO- (acetate) = B (for base) and CH3COOH(acetic acid) = A (for acid).
So what you have is B/A = 1.74 and we can rearrange that to
B = 1.74 x A (I would carry that out to one more place; i.e., instead of 1.74 I would go with 1.738.
Now you know that
B + A = 0.1 so substitute for B from above to obtain
1.738A + A = 0.1
and solve for A, then B.
That's how you obtain A and B (concn in moles/L = M). Then in short, the rest of the problem is
How much acid is in the buffer of 5.00? That is 150 mL x (A) = ??
How much base is in the buffer of 5.00?
That is 150 mL x (B) = ??
Now, when you add the 0.280 M HCl what is happening?
Base + HCl ==> acid + Cl^-
So how much acid are you adding? That is 0.280 M x 5.60 mL = ??= I'll say x.
So you add x to acid and subtract x from the base, then reset pH = pKa + log (B/A) and solve for the new pH.
I did a quickie calculation and obtained 4.81 or so. You need to redo the whole thing. Check my work. Does that answer make sense? Yes, because it was pH = 5.00 and we added HCl, a strong acid to it, so it should become more acid and 4.81 is more acid than 5.00.
Chemistry - A beaker with 150 mL of an acetic acid buffer with a pH of 5.00 is ...
chemistry help!! - A beaker with 195 mL of an acetic acid buffer with a pH of 5....
Chemistry - A beaker with 200 mL of an acetic acid buffer with a pH of 5.00 is ...
Chemistry - A beaker with 100 mL of an acetic acid buffer with a pH of 5.00 is ...
Chemistry - I don't get this at all. A beaker with 105mL of an acetic acid ...
CHEMISTRY HELP! - (1) A beaker with 165 mL of an acetic acid buffer with a pH of...
Chemistry - You are asked to prepare 500. mL of a 0.150 M acetate buffer at pH 5...
school - What is the pH of 0.1 M formic acid solution? Ka=1.7e10-4? What ...
Chemistry - A buffer contains 5.00 M acetic acid and 5.00 M acetate anion. ...
Chemistry - Pure acetic acid, known as glacial acetic acid, is a liquid with a ...
For Further Reading