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Thread: Degree of ionisation

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    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?


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    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).

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    Re: Degree of ionisation

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

    so A or C



    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
    Last edited by HeroicPandas; 24 Jun 2013 at 10:57 PM.

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    Re: Degree of ionisation

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

    so A or C



    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?

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    Re: Degree of ionisation

    Quote Originally Posted by Kimyia View Post
    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

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    Re: Degree of ionisation

    The answer is C.

    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.
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    Re: Degree of ionisation

    Quote Originally Posted by AnimeX View Post
    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!

    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
    Last edited by HeroicPandas; 24 Jun 2013 at 11:03 PM.

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    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
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    ^what?
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    Re: Degree of ionisation

    Quote Originally Posted by golgo13 View Post
    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,

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

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    Re: Degree of ionisation

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

    In this question, imagine this chemical equilibrium in ur mind!

    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?

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    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.
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    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.

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    Re: Degree of ionisation

    Quote Originally Posted by _luke_ View Post
    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.
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