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    i thought that was weird paper, the nickel question, especially. i went completely mad about the ionic equation, for the silver doesn't change in oxidation number!...i did an ester for the displayed structure...but couldn't locate a chiral centre (so i think i am wrong...), the last equation i got the formula i think and the reaction goes to completion. the born haber cycle threw me when i looked at it first, but then it was ok!...it seems nuffield has concentrated on maths based questions more this time round, as the unit 4 paper was similar (full of maths, but was great )
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    what kind of next exam was that, i got some next arene ring with four carbons, got a weird Nickel oxidation state (what was the answer), electrode potential was weird1!!

    (Original post by wodoodporny)
    my molecular formula was C10 H12 02; a lot of others seemed to have got this

    according to the info in the question, its an ester ie:sweet smelling

    it has a ketone group

    it has a hydroxyl group

    in this case how can there be 2 O atoms, since an ester grouping itself has 2 atoms?

    my Mr must be wrong, im curious to know what others got
    i dont think itwas def an ester
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    I really hated that paper. for th first time in an exam I've had to guess stuff and even leave some questions. I really hated the last 2 questions, and thicnk I got 0 for the both! I need to get an A in chemistry, and if I just get the As in 4 and 5, i need 76UMS from that paper. What sort of raw mark would that be, I belive that the marks are increased UMS. It was worse than the physics synoptic and that's saying something. Made a few silly errors - the displayed formula in the first question, 2nd q was OK, but the one with the amine and the SEPs was pure hell. That paper was some kind of sick joke.
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    I'm just confused about born-haber cycle value....

    Did you guys get an enthalpy change ofsolution of -31.6 kj or round about?
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    Yes, I got -31 point something. The entropy of the surroundings was around one hundred and something, anyway.

    The first compound, there was definitely a phenol there, and definitely a ketone group. The sweet smelling thing was thrown in at the start, but I couldn't get an ester out at all, so I just ignored it and tried to put in as many of the other features as possible.
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    Crap, i got -34.6 I remember now. My Surrounding was like +119.something
    Nuffield don't award carry on marks do they?
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    great...i got some huge positive no...are u talking about the enthalpy change of solution here? how did u calculate the value of H2?
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    I just did Lattice - delta H2
    for delta H2 looked things up and just reversed the signs when the arrows were reversed.

    But according to a website the actual value is -21kJ mol^-1

    I got -34.6 so it looks like we're both fluffed.
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    the answer was minus 30 something or other. i thought it would be a positive value since delta H 2 was -900 and something. Nonetheless it was only one mark, the rest of the paper was straight foward.
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    christ it was horrible. i need 3 As for cambridge and all my exams are going awful. keep remembering stupid things i did wrong, which is even more annoying than the fact i didn't understand half the paper. i got high As last year so i suppose it might be alright. :confused: anyone know about what i'd need to get to scrape it? i suppose the grade boundaries will have to be low if we all hated it. fingers crossed! i'd be very surprised if i scored more than half marks.
    oh well everyone try and enjoy summer. im trying to revise politics now. bloody a levels.
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    im so silly. i got all my units wrong.
    for all the entropy of system and surroundings i wrote kJ mol instead of J mol K
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    Did the calculation again, it was for the second time -35.6kJ mol^-1
    Lattice = -958
    Delta H2 = -(Enthalpy change of atomisation [Ag] + Em1[Ag] +Eaff[F] + enthalpy change of atomisation [F]) + (enthalpy change of formation [Ag^+(aq)] + (enthalpy change of formation [F^-(aq)] )

    = - (284.6 + 731 + -328 + 79) + (105.6 + -332.6)
    = -766.6 + -227
    = -993.6

    Enthalpy change of solution = delta H2 - Lattice energy
    = -993.6 - (-958)
    = -35.6 kJ mol^-1

    Done it over and over...all values from the book of data. I remember getting this exacy value, but who's wrong, Nuffield's data book? Or the standard enthalpy change of solution of AgF according to....google ?
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    :eek:
    (Original post by coulson_2000)
    organic acids are weak acids so it did have a cooh group
    the bradys reagent told you it had a carbonyl group C=O
    the benedicts test told you it wasnt an aldehyde
    the absorbtion at 830 told you it was an arene ring with 2 adjacent hydrogens
    cant remember what the other test were

    over all i didt think the paper was too bad - just triky - made me think a lot!
    what you are saying is right guys, im certain about this tho:
    yes brady reagent is for the c=o group BUT carb acid eg methoxybenzoic WILL give both orage precip w bradys BUT WOULD ALSO BE STRONG ENOUGH TO GIVE CO2.

    therefor it couldnt hav bin a carboxylic, it must hav been phenolic with an aldehyde group (gave precip w benedicts) i cant remem xactly but i think i gt sumtin like a phenol with propanal type bit stuck on it

    anyway im so f**** glad you guys all found it hard!! im sorry but i really was CRYING MY SOUL OUT i rekon i got a D for this one and for the rest of my units i got 81/90 or over, all that work WASTED.
    LOW GRADE BOUDARIES!!!!YAY!!!!if we all suffered, mus be hard paper, tho i thought if i revisd betr wud have dun betr than the past pprs. im so p***d i thoght ther was a doulble blank pg @ the end, so missed out the easiest Q!!! damn!!!

    What did ne 1 get for the value of x in the nickel complex? i got 1 every1 else got 2! an how the hell did yu draw the electrode graf thing?
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    (Original post by cipapfatso)
    Did the calculation again, it was for the second time -35.6kJ mol^-1
    Lattice = -958
    Delta H2 = -(Enthalpy change of atomisation [Ag] + Em1[Ag] +Eaff[F] + enthalpy change of atomisation [F]) + (enthalpy change of formation [Ag^+(aq)] + (enthalpy change of formation [F^-(aq)] )

    = - (284.6 + 731 + -328 + 79) + (105.6 + -332.6)
    = -766.6 + -227
    = -993.6

    Enthalpy change of solution = delta H2 - Lattice energy
    = -993.6 - (-958)
    = -35.6 kJ mol^-1

    Done it over and over...all values from the book of data. I remember getting this exacy value, but who's wrong, Nuffield's data book? Or the standard enthalpy change of solution of AgF according to....google ?

    sorry is me again, i cud only do this and q1 but im sur i did them defn8ly r8
    i got -35.6kj mol in the xm plz tel me im r8??!! i need this grade!!
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    (Original post by magiccarpet)
    :eek:

    what you are saying is right guys, im certain about this tho:
    yes brady reagent is for the c=o group BUT carb acid eg methoxybenzoic WILL give both orage precip w bradys BUT WOULD ALSO BE STRONG ENOUGH TO GIVE CO2.

    therefor it couldnt hav bin a carboxylic, it must hav been phenolic with an aldehyde group (gave precip w benedicts) i cant remem xactly but i think i gt sumtin like a phenol with propanal type bit stuck on it

    anyway im so f**** glad you guys all found it hard!! im sorry but i really was CRYING MY SOUL OUT i rekon i got a D for this one and for the rest of my units i got 81/90 or over, all that work WASTED.
    LOW GRADE BOUDARIES!!!!YAY!!!!if we all suffered, mus be hard paper, tho i thought if i revisd betr wud have dun betr than the past pprs. im so p***d i thoght ther was a doulble blank pg @ the end, so missed out the easiest Q!!! damn!!!

    What did ne 1 get for the value of x in the nickel complex? i got 1 every1 else got 2! an how the hell did yu draw the electrode graf thing?
    It didn't react with benedicts so if anything it was a ketone side group.
    However I am very confused...Nuffield buggered it. Why say it was responsible for a sweet fruity smell of berries and then go on to give evidence which contradicted an ester?
    I think it was a phenol with a ketone group sidechain arranged in such an arrangement that there was a chiral centre. Still, they buggered that question up bad.

    SEP graph was straight forward I thought. Both equations had an Ecell > +0.6V so both would go to completion/large Kc

    Either way what's done is done.
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    (Original post by magiccarpet)
    sorry is me again, i cud only do this and q1 but im sur i did them defn8ly r8
    i got -35.6kj mol in the xm plz tel me im r8??!! i need this grade!!
    Yeah i got that too. So entropy of system ended up being negative but outweighed by entropy of surroundings as it was positive. Stotal was positive so it was soluble.
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    (Original post by sorcetags&codes)
    ****in hell. :eek: got to be the hardest exam i have ever taken in my life. i'm sure i've failed that, and i dont think i did to well on food science. thought i found food science easy, i'm beginning to think to easy, so i must have done something wrong.

    for the first question did anyone get an ester?

    i'm dead upset...i hate chemistry now. :mad: :mad:
    YEAH I F*** AGREE SO SO MUCH WITH U THIS IS EXACTLY EXACTLY HOW I FEEL WHAT A PILE OF SH** :mad: :mad: :mad:
    F*** CHEM
    JUS F** CHEM
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    [QUOTE=cipapfatso]It didn't react with benedicts so if anything it was a ketone side group.
    However I am very confused...Nuffield buggered it. Why say it was responsible for a sweet fruity smell of berries and then go on to give evidence which contradicted an ester?
    I think it was a phenol with a ketone group sidechain arranged in such an arrangement that there was a chiral centre. Still, they buggered that question up bad.

    SEP graph was straight forward I thought. Both equations had an Ecell > +0.6V so both would go to completion/large Kc

    Either way what's done is done.[/QUOT

    aldehydes smell too, not just esters
    ne way i dunno abt them but was me tht buggered up that question bad
    actually, buggered up all the qs bad :mad: :confused:

    (Original post by magiccarpet)

    aldehydes smell too, not just esters
    ne way i dunno abt them but was me tht buggered up that question bad
    actually, buggered up all the qs bad :mad: :confused:
    It wasn't an aldehyde though. An aldehyde would have reacted with Benedict's.

    By the way (not to you just in general), Brady's reagent comes up negative for carboxylic acids. The -OH modifies the properties of the =O; it isn't the same as the =O in an aldehyde or ketone.

    C=O on its OWN is a carbonyl group - in acids it's a carboxyl group together with the -OH.

    Brady's reagent is only positive for C=O in aldehydes/ketones (I am not sure about esters, but I don't think it would be positive as an ester is really a substituted carboxylic acid group and not a plain carbonyl group).
 
 
 
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