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Topic: Species in Solution  (Read 6834 times)

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Offline Messi

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Species in Solution
« on: October 13, 2012, 08:58:58 PM »
If I have a solution of Sodium Acetate (CH3OH), what species would I expect in solution in order of  decreasing concentration?

I said:
CH3COONa
H2O
CH3COOH
NaOH
H+ & OH-

I wasn't sure where I would put Na+ and CH3COO- as I guess some of these ions would be expected in the solution, no?
« Last Edit: October 13, 2012, 09:44:53 PM by Messi »

Offline Dan

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Re: Species in Solution
« Reply #1 on: October 14, 2012, 05:43:52 AM »
Quote
I have a solution of Sodium Acetate (CH3OH)

A methanolic solution of sodium acetate? Can you explain how you propose to form water from sodium acetate and methanol?
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Offline Messi

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Re: Species in Solution
« Reply #2 on: October 14, 2012, 09:26:59 AM »
Sorry, I meant Sodium Acetate (CH3COONa)! I had a brain fart when I wrote the molecular formula!

Offline Arkcon

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Re: Species in Solution
« Reply #3 on: October 14, 2012, 09:41:23 AM »
I wasn't sure where I would put Na+ and CH3COO- as I guess some of these ions would be expected in the solution, no?

Sure, can you work on the rest?  How much [NaAcetate] molecular do you expect to exist an aqueous solution?
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Offline Messi

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Re: Species in Solution
« Reply #4 on: October 14, 2012, 10:15:24 AM »
Ok I guess I'll put this as my list in order of decreasing concentration:

I said:
CH3COONa
H2O
CH3COO- & Na+
CH3COOH
NaOH
H+ & OH-

I think the above list is correct? It makes sense to me in a conceptual manner.

Offline Borek

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Re: Species in Solution
« Reply #5 on: October 14, 2012, 10:21:49 AM »
Acetic acid is a weak one, so you should expect quite strong hydrolysis.
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Offline Arkcon

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Re: Species in Solution
« Reply #6 on: October 14, 2012, 10:54:49 AM »
So you expect sodium acetate to exist in solution mostly as a molecular species?  So, comparing a solution of sodium acetate in water, you think the properties are more like sucrose in water, and less like sodium chloride in water?  That is to say, sodium acetate isn't very ionic in character?  A solution won't conduct electricity, for example?
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Offline fledarmus

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Re: Species in Solution
« Reply #7 on: October 14, 2012, 11:39:34 AM »
Why would you expect less water than sodium acetate? What is the solubility of sodium acetate in water?

Offline Messi

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Re: Species in Solution
« Reply #8 on: October 14, 2012, 03:43:45 PM »
Well here is my rational:

There are two equilibriums going on... one of them is:
H2O :rarrow: OH + H
The other one is:
CH3COONa + H20 :rarrow: CH3COOH + NaOH

H2O rarely breaks down into OH and H so these should be in the lowest concentration. NaOH is a strong base so dissociates almost completely so there should not be much NaOH left. If NaOH reacts with CH3COOH then there should not be much CH3COOH either?

So my list is:
CH3COONa
H2O
CH3COO- & Na+
CH3COOH
NaOH
H+ & OH-
« Last Edit: October 14, 2012, 03:51:17 PM by Borek »

Offline Borek

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Re: Species in Solution
« Reply #9 on: October 14, 2012, 03:50:23 PM »
You can safely assume acetate is dissociated 100%. You can also assume there is almost no NaOH in the solution, as a strong base it is 100% dissociated as well.

You are still missing the hydrolysis part which is what the question is most likely about.
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Offline Messi

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Re: Species in Solution
« Reply #10 on: October 14, 2012, 06:49:31 PM »
Hydrolysis part? Didn't I show the Sodium acetate being hydrolysed into NaOH and acetic acid?

Offline Borek

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Re: Species in Solution
« Reply #11 on: October 15, 2012, 04:03:27 AM »
You listed them, but you ignored other hydrolysis products.
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Offline Messi

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Re: Species in Solution
« Reply #12 on: October 15, 2012, 06:16:13 AM »
Do you mean... H2O + H2O :rarrow: H3O + OH ?
« Last Edit: October 15, 2012, 06:25:00 AM by Borek »

Offline Borek

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Re: Species in Solution
« Reply #13 on: October 15, 2012, 06:24:53 AM »
No.

Write reaction equation of the CH3COO- hydrolysis. What are the products?
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Offline Messi

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Re: Species in Solution
« Reply #14 on: October 15, 2012, 06:27:52 AM »
Did I not already write them?  ???

CH3COONa + H20  :rarrow: CH3COOH + NaOH

or

CH3COO + H20  :rarrow: CH3COOH + OH

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