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    (Original post by shiney101)
    http://filestore.aqa.org.uk/subjects...W-QP-JUN08.PDF

    Can someone help me with q1di?
    It stays at 4.20. Water only partially dissociates and very weakly at that. Therefore it only changes pH by +- 0.01 if that. mostly, doesn't change pH
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    (Original post by Gezza_O'Brien)
    So the 5 peaks on the M/Z are
    Carbon-12
    Hydrogen-1
    Oxygen-16
    Chlorine-35
    Chlorine-37

    And then the for the most abundant peak
    1) get an average abundance for Cl-35 and Cl-37

    So (37x25+35x75)/100

    Which gives you 35.5

    2)most abundant peak is the molecular ion
    So basically add up the Mr

    12*12 + 1*4 + 2*16 + 4*35.5 = 322.0



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    your explanation for part a is wrong. its the configurations of Cl 35 and Cl 37

    Peak 1: all 4 Cls are 35
    peak 2: 3 Cls are 35 and 1 is Cl 37
    peak 3: 2 Cls are 35 and 2 Cls are 37
    etc.

    so 5 different peaks
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    (Original post by Gezza_O'Brien)
    Yeah exactly. So if you were to add, say, HCl instead of NaOH, then there is more H+ ions in the equilibrium that need to be used, so the equilibrium shifts to the left (to use up H+) so there is less Y- and more HY, so you take the moles of HCl from Y- and you add them to HY, then put the new moles into Kc blah blah blah, does that make sense? Tbf it's pretty confusing but you've just got to think about it in terms of what's happening to the equilibrium


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    yh sort of I will look into it a bit later,

    Do you mind helping me with 4ei and 4eii.
    I thought NaOH causes the amino acid to be split up again.
    And Im not sure what ethanoyl chloride dos
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    Just for Reference guys;

    Terylene is a polyester made from 1-4 benzene dicarboxylic acid + ethane-1-2-diol

    Kevlar is a polyamide - Benene 1-4 diamine + Benzene 1-4 dicarboxylic acid

    Nylon 6-6 - Polyamide - 1-6 diaminohexane + 1--6 hexanedioic acid
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    (Original post by ravichauhan11)
    your explanation for part a is wrong. its the configurations of Cl 35 and Cl 37

    Peak 1: all 4 Cls are 35
    peak 2: 3 Cls are 35 and 1 is Cl 37
    peak 3: 2 Cls are 35 and 2 Cls are 37
    etc.

    so 5 different peaks
    Oh crap sorry. There was me thinking I actually understood this lmao


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    Checklist for Chem4

    - https://94300b5f86746b14725de6267cbd...%20A-level.pdf
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    (Original post by Super199)
    yh sort of I will look into it a bit later,

    Do you mind helping me with 4ei and 4eii.
    I thought NaOH causes the amino acid to be split up again.
    And Im not sure what ethanoyl chloride dos
    NaOH is a strong base, which functional group of the amino acid will react with the base?

    For the reaction with Ethanoyl Chloride, what part of the amino acid will act as a nucleophile?
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    (Original post by Greenemma)
    It stays at 4.20. Water only partially dissociates and very weakly at that. Therefore it only changes pH by +- 0.01 if that. mostly, doesn't change pH

    OH that makes sense, thank you so much!
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    (Original post by Parallex)
    NaOH is a strong base, which functional group of the amino acid will react with the base?

    For the reaction with Ethanoyl Chloride, what part of the amino acid will act as a nucleophile?
    Im not sure sorry
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    (Original post by Gezza_O'Brien)
    Attachment 548885

    I find it helps to write out the actual chemical equations so you can see what's going on


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    What year is this question from?
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    (Original post by Super199)
    Im not sure sorry
    Bases react with acids in a neutralisation reaction, an amino acid has a carboxylic acid group.

    The reaction with ethanoyl chloride is the exact same as any nucleophile attacking the electron-deficient carbon. Reaction between ammonia and ethanoyl chloride? Just so happens that an amino acid has the N with a lone pair that will react in the same way.
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    (Original post by Cakey_101)
    What year is this question from?
    Jan 2011. Very worthwhile practicing these questions, you can lose a decent amount of marks if you don't know what you're doing


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    (Original post by Parallex)
    Yeah. You're looking at how much excess there is after neutralisation. If it's a strong acid then you have to multiply by 2 because it will fully dissociate and 2H+ is available for neutralisation.
    im so confused you've bypassed my question and contradicted yourself so many times
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    (Original post by Gezza_O'Brien)
    Can anyone think of anything from AS we need to go over? Like do we need to know like the UV thingy and shapes and stuff like that?


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    Just gonna bump this lmao I need answers please


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    (Original post by Sniperdon227)
    im so confused you've bypassed my question and contradicted yourself so many times
    2 people including myself have tried answering whatever you're asking, I literally don't even know what else you want me to say. There's nothing to it other than that...
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    (Original post by Parallex)
    NaOH is a strong base, which functional group of the amino acid will react with the base?

    For the reaction with Ethanoyl Chloride, what part of the amino acid will act as a nucleophile?
    Reacts with COOH - weak acid strong base

    B.) the NH2 - it's a nucleophilic addition elimination mechanism

    I wrote the mechanism out if it helps you imagine it

    OOPs; just realised i didn't do the other COOH group, but that would be the same too! Sorry
    Attached Images
     
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    (Original post by Parallex)
    Bases react with acids in a neutralisation reaction, an amino acid has a carboxylic acid group.

    The reaction with ethanoyl chloride is the exact same as any nucleophile attacking the electron-deficient carbon. Reaction between ammonia and ethanoyl chloride? Just so happens that an amino acid has the N with a lone pair that will react in the same way.
    hmm ok but it seems quite complicated to draw?
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    (Original post by Super199)
    hmm ok but it seems quite complicated to draw?
    Eh not really. Look at the post above yours.
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    (Original post by hopingmedicinae)
    Reacts with COOH - weak acid strong base

    B.) the NH2 - it's a nucleophilic addition elimination mechanism

    I wrote the mechanism out if it helps you imagine it

    OOPs; just realised i didn't do the other COOH group, but that would be the same too! Sorry
    (Original post by Parallex)
    Eh not really. Look at the post above yours.
    Got it cheers
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    If it doesn't ask you to leave your answer to a specific d.p, does that mean you can round it to any decimal place?? doesn't really say on the mark schemes???
 
 
 
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