1. ## Degree of ionisation

Please explain what "degree of ionisation" means, my understanding was the ability to dissociate ions (is this wrong?).

What would be the answer to this question?

2. ## Re: Degree of ionisation

I probably wouldn't use the word 'ability'. I think degree of ionisation is more so the extend to which the substance will dissociate or the proportion of particles that have dissociated. i.e. high degree of ionisation means the majority or virtually all of the particles will dissociate into ions (like with HCl), low degree of ionisation means only a small percentage of the particles present will dissociate into ions (e.g. acetic acid).

3. ## Re: Degree of ionisation

Add water --> dilution --> decrease acidity --> increases pH

so A or C

$\small CH_3COOH_{(aq)} + H_2O_{(l)} \rightleftharpoons CH_3COO^-_{(aq)} + H_3O^+_{(l)}$

If we decrease acidity...that means less H3O+ ions, by Le Chatelier's Principle, a disturbed system shifts to counteract change, hence shifts to the right to produce more H3O+, increasing deg of ionisation

is this correct?
only thing i can think of because increasing vol. of water will have no effect

so is it C?

EDIT: ITS IN BOLD

4. ## Re: Degree of ionisation

Originally Posted by HeroicPandas
Add water --> dilution --> decrease acidity --> increases pH

so A or C

$\small CH_3COOH_{(aq)} + H_2O_{(l)} \rightleftharpoons CH_3COO^-_{(aq)} + H_3O^+_{(l)}$

If we increase acidity...that means less H3O+ ions, by Le Chatelier's Principle, a disturbed system shifts to counteract change, hence shifts to the right to produce more H3O+, increasing deg of ionisation

is this correct?
only thing i can think of because increasing vol. of water will have no effect

so is it C?
hey, when you say increase acidity why does that mean less H3O+? I thought the more acidic something was, the more H3O+?

EDIT: and yes it is C , can you further explain it though?

5. ## Re: Degree of ionisation

Originally Posted by Kimyia
I probably wouldn't use the word 'ability'. I think degree of ionisation is more so the extend to which the substance will dissociate or the proportion of particles that have dissociated. i.e. high degree of ionisation means the majority or virtually all of the particles will dissociate into ions (like with HCl), low degree of ionisation means only a small percentage of the particles present will dissociate into ions (e.g. acetic acid).
Hi, but what does water do to it? I'm still confuzzled

6. ## Re: Degree of ionisation

Obviously, if you dilute an acid, pH increases (less acidic) so that leaves A or C.

Degree of ionisation refers to how many acetic acid molecules will break apart to form ions, that is, as a proportion of all acid molecules, how many of them will dissociate. To explain this, the Le Chatelier's principle reference is correct.

7. ## Re: Degree of ionisation

Originally Posted by AnimeX
hey, when you say increase acidity why does that mean less H3O+? I thought the more acidic something was, the more H3O+?

EDIT: and yes it is C , can you further explain it though?
sorry made a mistake, sorry for the confusion

In this question, imagine this chemical equilibrium in ur mind!
$\small CH_3COOH_{(aq)} + H_2O_{(l)} \rightleftharpoons CH_3COO^-_{(aq)} + H_3O^+_{(l)}$
Add water --> dilution --> decrease acidity --> less H3O+ ions --> system wants to produce more H3O+ to compensate for the loss (Le Chatelier's Principle) --> equation shifts to the right to produce mroe H3O+ --> shifting to the right means more acetic acid molecules will ionise into ethanoate and hydronium ions

8. ## Re: Degree of ionisation

alternatively you could use c1v1=c2v2 you'll see that the value of c decrease and dumping that back into -log(conc) you'll see that rise

9. ^what?

10. ## Re: Degree of ionisation

Originally Posted by golgo13
alternatively you could use c1v1=c2v2 you'll see that the value of c decrease and dumping that back into -log(conc) you'll see that rise
no

Firstly, $pH = -log_{10}[H^+]$

secondly, acetic acid doesnt not completely ionise and hence u dont know the exact concentration of H+, hence u cannot find the exact pH

11. ## Re: Degree of ionisation

Originally Posted by HeroicPandas
sorry made a mistake, sorry for the confusion

In this question, imagine this chemical equilibrium in ur mind!
$\small CH_3COOH_{(aq)} + H_2O_{(l)} \rightleftharpoons CH_3COO^-_{(aq)} + H_3O^+_{(l)}$
Add water --> dilution --> decrease acidity --> less H3O+ ions --> system wants to produce more H3O+ to compensate for the loss (Le Chatelier's Principle) --> equation shifts to the right to produce mroe H3O+ --> shifting to the right means more acetic acid molecules will ionise into ethanoate and hydronium ions
thanks, this makes much more sense!

so, just confirming: acetic molecules ionising to ethanoate and hydronium is correct, in terms of wording?

12. Acetic acid can react with water to produce acetate and hydronium ions in solution.

The problem with yours is that you forget to mention water so you can't make hydronium ions.

13. ## Re: Degree of ionisation

Sorry to start the thread up again, but just to point out an error. The relative concentration of each of the products (bar water) would remain the same (the concentration of the species in the above equilibrium would be diluted by the same factor).

Hence, it isn't the fact that there is a decrease in hydrogen ions, but rather than there is an increase in the water species which drives the equilibrium reaction forward.

14. ## Re: Degree of ionisation

Originally Posted by _luke_
Sorry to start the thread up again, but just to point out an error. The relative concentration of each of the products (bar water) would remain the same (the concentration of the species in the above equilibrium would be diluted by the same factor).

Hence, it isn't the fact that there is a decrease in hydrogen ions, but rather than there is an increase in the water species which drives the equilibrium reaction forward.
yes this post is correct
Degree of ionisation

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