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OCR Salters Chemistry F335 12th June 2013 Exam revision thread Watch

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    (Original post by ells-13)
    Was there a question asking to classify the reaction, condensation or addition and a reason for it???
    This was really misleading, jumping straight into it I saw an amide link and put condensation. After looking at it more carefully I noticed nothing had been lost from the monomers, and also the question after stated it was 100% atom economy - so had to be addition.
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    (Original post by Pandora's Box)
    Yeah I got that equation, but... a) does it matter which side the dot goes? I can't remember where I put it.. And b) did you have to label them initiation and termination because if so I didn't read the question.. :/
    the dot doesn't matter and it asked in the question for the type of radical reaction, i missed it that when i did the equation but saw that it was worth four marks so i read the questions again and saw it
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    (Original post by Sujman)
    What about a*
    Is it not just 90% so maximum of 107/120 if there was no cap of full UMS?
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    (Original post by abzy1234)
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    (Original post by suncake)
    But then the salt:acid conc ratio is still 2:1? Water dilutes them both so no effect?

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    Oh I do hope so! Thanks!
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    (Original post by Reina)
    Sticking random numbers in to help explain:

    I was thinking if you start off with 100 salt and 100 acid. Then half the acid is neutralised to form 50 acid and 50 salt which is added to the original salt. So you end up with 150 salt divided by 50 acid. So the ratio is 3?
    Acid + salt = water, though!

    I put exactly the same curly arrows as you.

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    (Original post by billybobs)
    This was really misleading, jumping straight into it I saw an amide link and put condensation. After looking at it more carefully I noticed nothing had been lost from the monomers, and also the question after stated it was 100% atom economy - so had to be addition.
    Ye addition but my reason was no small molecule was eliminated, is that right?
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    (Original post by ells-13)
    Was there a question asking to classify the reaction, condensation or addition and a reason for it???
    I think there was a "is this addition or a condensation" question as well as a "classify this reaction question" but I can't remember what kind of reactants were involved

    I think I put addition for the first one and elimination for the second.
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    (Original post by billybobs)
    This was really misleading, jumping straight into it I saw an amide link and put condensation. After looking at it more carefully I noticed nothing had been lost from the monomers, and also the question after stated it was 100% atom economy - so had to be addition.
    But where does the hydrogen atom go from the OH groups of ethandiol? Crap. Another mark lost.

    (Original post by hayleyvictoria)
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    (Original post by C.JTop)
    addition 100% yield
    How many marks was that
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    (Original post by Reina)
    I think there was a "is this addition or a condensation" question as well as a "classify this reaction question" but I can't remember what kind of reactants were involved

    I think I put addition for the first one and elimination for the second.

    i got additions then elimination too
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    (Original post by Reina)
    Did anyone divide Ka by three for the neutralisation of half the acid question?
    I think I did something like that. Cause originally the salt/acid ratio was 1/1 so if half the acid reacts and gets turned into salt, you get 1.5/0.5 which equals 3? So Ka = [H+] x 3? pH came out as 4.2 or something I think, can't remember..
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    (Original post by ells-13)
    Ye addition but my reason was no small molecule was eliminated, is that right?
    Mmmm, possibly. I put no molecules are lost AND two smaller monomer units join together to form one large polymer.
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    (Original post by Futuristicmedic)
    I reckon A = 85/120 ?


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    oh that would be nice, made so many little errors.
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    The polymerisation Question, what did people put..... what type of polymerisation was it?
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    Guys any ideas what the grade boundaries will be?

    I checked the previous papers and they all seem to be about 70% raw marks (84) = A. Hope they follow the same pattern
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    2 HCOOH + caco3 --> co2 + h2o + (Hcoo)2ca


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    and the isocyanate question, only one product formed thus no side reactions hence 100% atom economy.
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    (Original post by HTB)
    what did people put for the 'industrial use of hydrogen'? (i think that was the question!)
    Making ammonia using the haber process


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    (Original post by Pandora's Box)
    I think I did something like that. Cause originally the salt/acid ratio was 1/1 so if half the acid reacts and gets turned into salt, you get 1.5/0.5 which equals 3? So Ka = [H+] x 3? pH came out as 4.2 or something I think, can't remember..
    i got that too through halving ka - didn't understand wht was going on though
 
 
 
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