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    (Original post by man i)
    yeah i sort of messed up the equation because of my bad set up, i got the salt etc and done molex1000/v to get conc for both the left over solution and salt and then messed up my number by using 9.25x10-3 rather than my worked out concentration. so i shouldve got it right either way.

    just another question i wanted to ask for KC if the volume of the container increases say 1.5dm3 to 3.0dm3 it does not effect the kc does it or the conc right or does it effect the conc only. im really confused on these for some reason
    The only thing that affects Kc is Temp, nothing else. That the explanation you need really, for a simple Q, but i think its due to partial prssure and stuff like that .. for a harder one, doubt a hard one will come up .. but revise it if you want.
    and I do mess up a lot on doing the same, would recommend rechecking your work, or just doing the Q again , to check. Since its an easy mark to lose .. and we/I need all the marks we can get.
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    What do you do if OH is in excess when you add a base to a weak acid??
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    (Original post by meerkatinhiding)
    What do you do if OH is in excess when you add a base to a weak acid??
    I assume the Kw of the base should be given so that you solve the question? correct me if im wrong
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    (Original post by meerkatinhiding)
    What do you do if OH is in excess when you add a base to a weak acid??
    Take away all the Acid and add to the salt , like normal. But acid will be 0 in the EQ ,.do nothing with the extra base, since you cant really do anything with it from out A2 learning ( unless we have teh Kw; even then i doubt we could do it .. since we arent taught it , or i wasnt and its not in the book or past papers), this is why we never get that Q... since we just arent taught it well enough or at all.
    This has Never happened and i doubt it will, but revise it. I havent much since i dount itll come up and if it does... **** AQA, simple as.

    Also the above persons, will also make sense. Since then we can do something with the extra base .. but like i siad, its never happened so far.
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    (Original post by rimstone)
    Take away all the Acid and add to the salt , like normal. But acid will be 0 in the EQ ,.do nothing with the extra base, since you cant really do anything with it from out A2 learning ( unless we have teh Kw; even then i doubt we could do it .. since we arent taught it , or i wasnt and its not in the book or past papers), this is why we never get that Q... since we just arent taught it well enough or at all.
    This has Never happened and i doubt it will, but revise it. I havent much since i dount itll come up and if it does... **** AQA, simple as.

    Also the above persons, will also make sense. Since then we can do something with the extra base .. but like i siad, its never happened so far.
    Thanks!
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    (Original post by rimstone)
    Take away all the Acid and add to the salt , like normal. But acid will be 0 in the EQ ,.do nothing with the extra base, since you cant really do anything with it from out A2 learning ( unless we have teh Kw; even then i doubt we could do it .. since we arent taught it , or i wasnt and its not in the book or past papers), this is why we never get that Q... since we just arent taught it well enough or at all.
    This has Never happened and i doubt it will, but revise it. I havent much since i dount itll come up and if it does... **** AQA, simple as.

    Also the above persons, will also make sense. Since then we can do something with the extra base .. but like i siad, its never happened so far.
    wudnt u jus work out xs OH- divide by total volume... then divide it by Kw to find [h+]
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    Hey guys, just wanted to say that if anyone wanted a quick summary on everything you need to know for the course as a bit of last minute revision stuff then I made a thread. Don't know if it'll be useful but here:

    http://www.thestudentroom.co.uk/show....php?t=4159211

    Anyway good luck, hope it goes well for you all. :woo:
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    (Original post by rimstone)
    Take away all the Acid and add to the salt , like normal. But acid will be 0 in the EQ ,.do nothing with the extra base, since you cant really do anything with it from out A2 learning ( unless we have teh Kw; even then i doubt we could do it .. since we arent taught it , or i wasnt and its not in the book or past papers), this is why we never get that Q... since we just arent taught it well enough or at all.
    This has Never happened and i doubt it will, but revise it. I havent much since i dount itll come up and if it does... **** AQA, simple as.

    Also the above persons, will also make sense. Since then we can do something with the extra base .. but like i siad, its never happened so far.
    the questions with excess OH- come up loads. you just use kw
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    (Original post by Anon_98)
    Hey guys, just wanted to say that if anyone wanted a quick summary on everything you need to know for the course as a bit of last minute revision stuff then I made a thread. Don't know if it'll be useful but here:

    http://www.thestudentroom.co.uk/show....php?t=4159211

    Anyway good luck, hope it goes well for you all. :woo:
    legend, will you be doing the same for unit5?
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    (Original post by rimstone)
    Take away all the Acid and add to the salt , like normal. But acid will be 0 in the EQ ,.do nothing with the extra base, since you cant really do anything with it from out A2 learning ( unless we have teh Kw; even then i doubt we could do it .. since we arent taught it , or i wasnt and its not in the book or past papers), this is why we never get that Q... since we just arent taught it well enough or at all.
    This has Never happened and i doubt it will, but revise it. I havent much since i dount itll come up and if it does... **** AQA, simple as.

    Also the above persons, will also make sense. Since then we can do something with the extra base .. but like i siad, its never happened so far.
    You would use the base dissociation constant, Kb, if there was an excess of a weak base. If there is an excess of a strong base, you just use Kw, to find [H+]. However, we are not tested on questions using Kb, it's either an excess of weak acid or an excess of a strong base.
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    (Original post by Jpw1097)
    You would use the base dissociation constant, Kb, if there was an excess of a weak base. If there is an excess of a strong base, you just use Kw, to find [H+].
    oh well if its weak base it wont come up as that isnt on the spec at all so i wouldn't worry about kb
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    (Original post by Hadigy)
    Guys - look out for properties of fats/oil, m+4 peak, chromatography, converting sodium salts back to fatty acids, half equivalence, aspirin, dative covalent bonding amines, properties of amino acids as solids and liquids, disposing polymers, diprotic acids.
    m+4 peak?
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    (Original post by Hadigy)
    Guys - look out for properties of fats/oil, m+4 peak, chromatography, converting sodium salts back to fatty acids, half equivalence, aspirin, dative covalent bonding amines, properties of amino acids as solids and liquids, disposing polymers, diprotic acids.
    why?
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    (Original post by Kaya22)
    oh well if its weak base it wont come up as that isnt on the spec at all so i wouldn't worry about kb
    Exactly.
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    Hey, sorry if it's already been mentioned I just skipped to the end. Does anyone know where I can find the WJEC CH4 and CH5 threads if there are some??
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    (Original post by Hadigy)
    Guys - look out for properties of fats/oil, m+4 peak, chromatography, converting sodium salts back to fatty acids, half equivalence, aspirin, dative covalent bonding amines, properties of amino acids as solids and liquids, disposing polymers, diprotic acids.
    what's the M+4 peak??
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    (Original post by Ultracrepidarian)
    legend, will you be doing the same for unit5?
    Yes, planning to but I've got quite a few exams next week so I'm worried I won't be able to fit it in.
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    (Original post by Ebaysass)
    what's the M+4 peak??
    I found it in the cgp book, it is just when you have 2 x +2 isotopes such as 2 x br81 bonded to the same compound.
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    (Original post by Hadigy)
    I found it in the cgp book, it is just when you have 2 x +2 isotopes such as 2 x br81 bonded to the same compound.
    oh ok, what page was that??
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    (Original post by Ebaysass)
    oh ok, what page was that??
    Page 123
 
 
 
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