#1
0.02L of 0.3M Acetic acid reacts with 0.01L of 0.5M NaOH. Find the ion concentration of acetate ions after the two solutions are mixed.

I don't really understand this. I know how to do this when both solutions are completely ionized, but since there is acetic acid, a weak acid, I'm a bit stuck on what to do. Can someone please give me a little walkthrough?

(I couldn't find the Science help thread, so please point me to it if you know where it is )

Thanks!
Last edited by kirbyrocknroll at Nov 11, 2008,
#2
****shit. I thought this was going to be easy. I just finished chem last year. Worst class evar.
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#3
hah dont think ve gotten to this yet. i spent a whole 2 hr class going over problems and no lab cuase people didn't do good on the test. but i haven't done ionized stuff yet. and yea-i thought this might be easy too =]
#4
i pity tha fool who starts a chem thread
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#5
I would convert both to moles, and then from there calculate the moles of H+ ions that would neutralize moles of OH- ions.
#7
molar mass/Atomic Mass = concentration

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#9
Quote by Skierinanutshel
just pretend they arent acids/bases, and figure out the limiting reagent, since they react in a 1 to 1 ratio

But then since its a weak base, wouldn't some of the acetate from the acetic acid react, and some not react? The way I would see is that there would be some acetate that doesn't react, and some that does react to form sodium acetate, which is soluble, and breaks up into sodium ions and acetate ions.

Would I just add those up? I asked someone how to do this, and they did this:

moles acetic acid = 0.02 L x 0.3 M = 0.006
moles NaOH = 0.01 L x 0.5 M = 0.005

CH3COOH + OH- >> CH3COO- + H2O

moles acetic acid = 0.006 - 0.005 = 0.001
moles acetate = 0.005
total volume = 0.02 + 0.01 = 0.03 L

concentration acetic acid = 0.001 / 0.03 = 0.033 M
concentration acetate = 0.005/ 0.03 = 0.17 M

What I don't get is how does that equation account for the acetate that is used to form the sodium acetate?
#10
it would all react.

weak/strong has nothing to do with "how much reacts" but rather the concentration of the H+ floating around, and the ability of an acid/base to form its conjugate counterpart.


edit: are you sure the salt that is formed is soluble in water? i dont know off hand if it is a soluble salt of not.
Last edited by Skierinanutshel at Nov 11, 2008,
#11
Quote by Skierinanutshel
it would all react.

weak/strong has nothing to do with "how much reacts" but rather the concentration of the H+ floating around, and the ability of an acid/base to form its conjugate counterpart.


edit: are you sure the salt that is formed is soluble in water? i dont know off hand if it is a soluble salt of not.

But wouldn't the fact that weak acids don't completely ionize mean that not all of the acetic acid would react? That and the fact that it's in excess? If I found out exactly how much acetic acid was in excess, would all of that be broken down into H+ and acetate ions?

So the products would just be sodium acetate and water?

EDIT: Yes, the salt would be sodium acetate, and all alkali metal salts are soluble.
Last edited by kirbyrocknroll at Nov 11, 2008,
#12
sneakytopedit: haha yeah i remember that now....its soluble in water (sorry if i'm a bit rusty, been a couple of years since this stuff)

Quote by kirbyrocknroll
But wouldn't the fact that weak acids don't completely ionize mean that not all of the acetic acid wouldn't react? That and the fact that it's in excess? If I found out exactly how much acetic acid was in excess, would all of that be broken down into H+ and acetate ions?

So the products would just be sodium acetate and water?



if the acetic acid is in excess (i really didnt look at it closely enough to tell), i guess you would have some that wouldnt react and left in solution.

i was just mentioning if it was in a 1:1 ratio. (anything in excess will not react with the limiting reagent).

and yes, it would still be in the ions form.
Last edited by Skierinanutshel at Nov 11, 2008,
#13
Ok, so I tried that, and I just ended up with the concentration being 0.006mol/0.03L = 0.2M of acetate ions.

Shouldn't the number of mols of the acetate ion be less than what we originally started with because the acetic acid doesn't completely dissociate into H+ and C2H3O2-?