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F334 (19/06/2013 9:00AM) - Salters Chemistry (Chemistry of Materials) Revision Thread Watch

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    (Original post by EstebanK0)
    I put down neutral, but I don't know if my reasoning was correct. Could you explain what would you write?
    I got that question wrong but I think I now know what the right answer is and understand why. Basically it was Neutral, as in water (a neutral solution) tyrosine forms a zwitterion, in that zwitterion, one H+ is gained and one H+ is lost, so overall there is no change, so its not anymore acidic than it is alkaline or vice versa, hope this helps
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    Didn't the question say something like it was hydrolysed using NaOH, and then put in water?

    And since phenols react with NaOH, would that therefore make an ion with an O- at the phenol, which would therefore still be ionic in water?

    I might be completely wrong but that was my thinking behind it.

    Did anyone ask their teachers?
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    (Original post by :)ella)
    Didn't the question say something like it was hydrolysed using NaOH, and then put in water?

    And since phenols react with NaOH, would that therefore make an ion with an O- at the phenol, which would therefore still be ionic in water?

    I might be completely wrong but that was my thinking behind it.

    Did anyone ask their teachers?
    I've forgotten tbh, but i dont think they'd ask us about the pH of a solution after you add an alkaline, wouldnt really make sense, so i think it was neutral solution - that would follow on from the zwitterion question
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    I wrote neutral because the charges cancel out. Couldn't think of anything else to write :/


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    (Original post by super121)
    I wrote neutral because the charges cancel out. Couldn't think of anything else to write :/


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    Pretty much what I wrote. Said it was neutral because one part is positive and the other is negative and therefore cancel each other out.
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    (Original post by EstebanK0)
    Pretty much what I wrote. Said it was neutral because one part is positive and the other is negative and therefore cancel each other out.
    I wrote it was neutral as charges cancel out. Tbh I didn't even see the phenol group and may have answered differently if I had seen that group. But in water its defiantly neutral as shown on Wikipedia. And I think it's something to do with the phenol only reacting with strong alkalis as it's a weak acid from looking in the cgp book.

    It was the previous question where NAOH was involved I think.
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    (Original post by Mattywooda)
    Google is your friend. Quick search shows tyrosine neutral and polar (http://www.elmhurst.edu/~chm/vchembo...structure.html).
    Ah crap. This was a 2 mark question

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    I did the N+H3 correctly but I removed the 'H' from the OH and putting O- on the benzene ring instead of the carbonyl group :/

    Do you think I'll still get a mark?
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    http://www.chemguide.co.uk/organicpr...l/acidity.html
    This says phenol is acidic, I'm so confused!
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    (Original post by :)ella)
    http://www.chemguide.co.uk/organicpr...l/acidity.html
    This says phenol is acidic, I'm so confused!
    Phenol is acidic, not very acidic though so solutions it creates will be acidic but will be effectively neutral compared to the solutions created by other acids, but nonetheless it will be very slightly acidic.
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    (Original post by EstebanK0)
    Ah crap. This was a 2 mark question

    Name:  561tyrsm.gif
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    I did the N+H3 correctly but I removed the 'H' from the OH and putting O- on the benzene ring instead of the carbonyl group :/

    Do you think I'll still get a mark?
    I did something similar, put the NH3+ and O- on carboxylic acid and O- on the phenol. My chemistry teacher said it could be right, as phenol does very slightly dissociate in water, but it's down to the mark scheme I guess, it may say "ALLOW O- on Phenol group", dunno. At least 1 mark if you did what I did though.
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    I put acidic for the zwitterion question. At the isoelectric point, the polar groups NH2 and COOH will ionise and charges will balance out but then I added that the phenol in the R group can partially ionise in water to form a phenoxide ion by donating a proton, so the overall solution would be slightly acidic. I am hoping that they allow neutral or acidic with reasoning!
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    (Original post by EstebanK0)
    Yeah, I'm having a cup of tea now. Feel like crap lol. Used the CGP as much as I could but didn't much do much in terms of past papers. Hopefully we'll all do good

    Good luck!
    Haha thanks I did the same haha
    Ahhh i think i preferred the f335 paper to be honest
    And I'm so annoyed, how the night before i stopped on Q3 june 2011... And Q4 was titration but I didnt know, so in the exam it came up and i was clueless Lost six marks right there. And I got home, saw the booklet and realised the next question was titration. Aghhhh could've gotten those six marks if i spent an extra 5 mins awake lol :/ Ah well it's over!
    How did you find it? Hope it went well!
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    (Original post by RainieXD)
    Haha thanks I did the same haha
    Ahhh i think i preferred the f335 paper to be honest
    And I'm so annoyed, how the night before i stopped on Q3 june 2011... And Q4 was titration but I didnt know, so in the exam it came up and i was clueless Lost six marks right there. And I got home, saw the booklet and realised the next question was titration. Aghhhh could've gotten those six marks if i spent an extra 5 mins awake lol :/ Ah well it's over!
    How did you find it? Hope it went well!
    I found it alright but now finding it reassuring when people are saying the same answers as I got. Fingers crossed it goes well!

    Yeah, titration was the last thing I looked at just before the exam. Although my memory of it was hazy during the exam, I got some of the key points in like burette and pipette and that the end point is a pink colour, although I didn't write permanent pink.
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    Hi,

    I was wondering if anyone had the june 2013 paper for this and the mark scheme?

    i'm resiting next summer so like to see where i went wrong

    thank youu

    pleaseee if anyone has it it'd be really useful
 
 
 
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