Join TSR now and get all your revision questions answeredSign up now
    Offline

    0
    ReputationRep:
    I'm resitting this paper next week. To be quite honest I haven't had a chance to prepare for it.. h e l p. What must I do..keep in mind I have an RS exam on friday /:
    Offline

    0
    ReputationRep:
    (Original post by Samtaylor47)
    I've just done June 2011 as well, got 50/60 which isn't too bad for me. But for the diazonium ion question, if you for the equation wrote it as C6H5N2+CL- and you'd get HCL as a product. Would i get the benefit of the doubt or would i lose the mark for including the cl?
    That was allowed in the markscheme.

    Chromotography separates a mixture of compounds by partition. This answer is acceptable for the two types on this specification, being Gas (Liquid) Chromotography and Thin Layer Chromotography.

    The compounds separate because they have different affinities for the stationary phase. They are carried by the mobile phase.

    The stationary phase is the phase that does not move in Chromotography. The mobile phase is the one that does.

    In TLC, the stationary phase is silica gel coated on a glass/plastic support. The mobile phase is a solvent. The sample is dotted onto the bottom of the card, and the solvent is filled up to just below it in a test tube. The solvent then travels up the card, taking the sample with it. The sample separates into its different components by the components adsorbing to the silica gel (by forming hydrogen bonds) with different strengths. Therefore polar molecules will adsorb more strongly to the silica and travel a shorter distance. If a component is not adsorbed to the silica gel it is travelling up the card with the solvent. Rf values can be calculated by distance traveled by component / distance traveled by solvent front.You can compare these values to a database of known Rf values to identify what compounds you have. However this is limited where the compounds are similar (stereoisomers etc) so have similar Rf values and cannot be differentiated.

    Therefore TLC separates components by adsorption (partition is acceptable).
    Above where I reference the silica gel you can use stationary phase. And where I use solvent you can use mobile phase.

    In GC the stationary phase is a high boiling point alkane (liquid) coated on the inside of the capillary tube (therefore it is supported). The mobile phase is an inert gas such as H2 (g). The sample is a mixture of gases, which is injected at the injection port, travels through the column (a long tube that goes round in a circle, to save space) which is inside a heated oven (as you are dealing with gases). Eventually the different components are detected at the detector, and their retention times are the time between injection and detection.
    The sample is in gaseous form when travelling with the mobile phase, however it can form VDW forces with the stationary phase and so dissolves. As the molecules are constantly moving eventually it will evaporate and continue moving through the column. Therefore what you are looking for are non polar and long chain molecules (no branches), these two factors combined form the most VDW forces and therefore the most interaction between a component and the stationary phase, giving that component the longest retention time. Polar molecules will pass through the quickest as they have the least affinity for the non polar stationary phase. GC is limited when gases have similar retention times, as you can't differentiate between them.

    Therefore GC separates components by partition.

    GC-MS is where the samples are put through a mass spectrometer after emerging from the column. This quantitatively identifies them as their mass spectra can be compared to those in a database to identify them.
    TLDR; both separate by partition!
    Offline

    0
    ReputationRep:
    Anyone have any predictions? I know this paper is hard to predict, so maybe a key list of re-occuring questions might be more applicable?
    Nevertheless anything to narrow down the topics so I can actual focus on stuff and not sit there, staring at the textbook panicking.. would be a great help!
    Offline

    0
    ReputationRep:
    Any good videos on internet which go over NMR spectroscopy well ?
    Offline

    2
    ReputationRep:
    do we need to know the specific examples for formation of kevlar from 1,4-dioic acid and 1,6-diaminohexane or are they just examples?
    • Study Helper
    Offline

    3
    ReputationRep:
    (Original post by AFC_123456789)
    do we need to know the specific examples for formation of kevlar from 1,4-dioic acid and 1,6-diaminohexane or are they just examples?
    I'm not sure but I'd learn them just in case
    Offline

    1
    ReputationRep:
    Could someone please tell me how you figure out splitting patterns in proton NMR for the question in Jan 13 below. Thanks Name:  image.jpg
Views: 155
Size:  503.8 KB
    Offline

    0
    ReputationRep:
    Does anyone have any predictions, Those That are really accurate usually with them... Really need them.??
    Offline

    0
    ReputationRep:
    (Original post by Lysipud)
    Could someone please tell me how you figure out splitting patterns in proton NMR for the question in Jan 13 below. Thanks Name:  image.jpg
Views: 155
Size:  503.8 KB

    We completed that paper for a mock! Here's my answers, is there anything you dont understand??
    Attached Images
     
    Offline

    0
    ReputationRep:
    (Original post by Lysipud)
    Could someone please tell me how you figure out splitting patterns in proton NMR for the question in Jan 13 below. Thanks Name:  image.jpg
Views: 155
Size:  503.8 KB
    The splitting patterns would be going top to bottom. Ch3 has no adjacent protons so singlet. Ch2 has 2 adjacent protons so triplet. Ch2 has 3 adjacent protons so quartet. Ch has 2 adjacent protons so splitting of triplet and finally cooh has no adjacent protons so singlet
    Offline

    1
    ReputationRep:
    (Original post by Raj Kang)
    The splitting patterns would be going top to bottom. Ch3 has no adjacent protons so singlet. Ch2 has 2 adjacent protons so triplet. Ch2 has 3 adjacent protons so quartet. Ch has 2 adjacent protons so splitting of triplet and finally cooh has no adjacent protons so singlet

    (Original post by ellenm_)
    We completed that paper for a mock! Here's my answers, is there anything you dont understand??
    Ah I get it =] thanks both!
    Offline

    1
    ReputationRep:
    Is it with the CIS fatty acid that it bends around so the molecules are side by side thus causing lots of points of contact so harder to break?
    Offline

    1
    ReputationRep:
    (Original post by Lysipud)
    Is it with the CIS fatty acid that it bends around so the molecules are side by side thus causing lots of points of contact so harder to break?
    No, cis do bend in same direction but trans arrange oppositely, molecules can get closer together, so more vdw, higher melting point. They also increase bad cholesterol

    Posted from TSR Mobile
    Offline

    2
    ReputationRep:
    (Original post by Mus1995)
    Read the thread I've posted all the papers.


    Posted from TSR Mobile
    ohh okay thanks
    Offline

    2
    ReputationRep:
    Perhaps someone can explain LDL's and HDL'S what they are and differences between them
    Offline

    2
    ReputationRep:
    hey guys please can you help and explain this for me:

    Write the formulae of the salts that would be formed when an EXCESS of C2H5NH2 reacts with h2so4 and ch3cooh (sulphuric acid and ethanoic acid)

    thanks a lot
    Offline

    1
    ReputationRep:
    (Original post by D4rth)
    No, cis do bend in same direction but trans arrange oppositely, molecules can get closer together, so more vdw, higher melting point. They also increase bad cholesterol

    Posted from TSR Mobile
    Ah so it's the trans that are harder to break! Okay thanks =]
    Offline

    0
    ReputationRep:
    hey does anyone know what page the jan 2013 paper is?
    Offline

    1
    ReputationRep:
    Can anyone recommend any good websites with revision packs/exam papers Pre 2010? Perks of being a gapper lol.

    And any predictions for the very big and the very small questions?

    Cheers
    Offline

    0
    ReputationRep:
    (Original post by AFC_123456789)
    hey guys please can you help and explain this for me:

    Write the formulae of the salts that would be formed when an EXCESS of C2H5NH2 reacts with h2so4 and ch3cooh (sulphuric acid and ethanoic acid)

    thanks a lot
    wierd question, i don't know where to go after you figure out the ions made, can anyone help?

    C2H5NH4+, HSO4-, CH3COO-
 
 
 
Poll
Should MenACWY vaccination be compulsory at uni?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Quick reply
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.