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Edexcel - Chemistry Unit 2 - 4 June 2013 Watch

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    (Original post by Jayqwe)
    Well unfortunately they have been rising quite substantially, for example the Jan 2013 paper=77/80, may 2012=75/80,may 2011=70/80,may 2010=72/80

    so I reckon for Tuesday it will be 79/80 for full ums lool
    thanks! I know I won't be getting full ums then!
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    (Original post by James A)
    The answer is C.

    Only three possible solutions.

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    oh yes!
    79+81=81+79 !

    Horrible mistake..I assumed the answer was D and basing on that I did the posible combinations for each atom!
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    (Original post by StUdEnTIGCSE)
    oh yes!
    79+81=81+79 !

    Horrible mistake..I assumed the answer was D and basing on that I did the posible combinations for each atom!
    Yeah you gotta remember that:

    Br(79)CH2CH2Br(81)

    is the same as

    Br(81)CH2CH2Br(79)

    I almost made the same error!
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    I am terrified of tomorrow, I hope it never comes
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    (Original post by James A)
    Possibly phosphorus, but I'd try to remember them all anyway! Unfortunately
    Ah god damn it so much to remember for this unit... there was far less stuff to remember in unit 4 !

    I'm just going to keep copying out the group 2 & 7 equations tomorrow morning on a load of paper That's what I did last year and it seemed to have worked. Get Section B & C out of the way first !


    (Original post by ASStudent)
    Do we need to know the sodium thiosulfate equations anyone?
    Unlikely, but it's good to remember this:

    I2 + 2S2O3^2- -----> 2I- + S4O6^2-
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    how do you carry out a flame test?
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    Calculate mean - sum of the two values all over 2. = 28.0cm^3

    Use moles=conc x (vol/1000) with the vol you just found = 2.8x10^-3

    Use the same formula again rearranged = 2.8x10^-3 / 25x10^-3 = 0.112 mol

    then multiply by 10 as it is ten times the vol. = 1.12 mol

    then use moles =mass/mr so 60 x 1.12 = 67.2 gdm^-3

    Hope this helps
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    (Original post by SophieL1996)
    how do you carry out a flame test?
    Use nichrome wire (as it is unreactive) and use conc HCl.

    Mix acid and powdered salt and pick up sample on the wire. Burn and observe.

    you have to make sure the wire is clean first by placing in the hcl then in the flame and then in hcl etc, until it burns with no colour.

    Hope this is accurate.
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    (Original post by beaver_tron)
    Calculate mean - sum of the two values all over 2. = 28.0cm^3

    Use moles=conc x (vol/1000) with the vol you just found = 2.8x10^-3

    Use the same formula again rearranged = 2.8x10^-3 / 25x10^-3 = 0.112 mol

    then multiply by 10 as it is ten times the vol. = 1.12 mol

    then use moles =mass/mr so 60 x 1.12 = 67.2 gdm^-3

    Hope this helps
    Thanks for the reply! ill have a read then see if I have any q's. Thanks!!!
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    (Original post by James A)
    Yeah you gotta remember that:

    Br(79)CH2CH2Br(81)

    is the same as

    Br(81)CH2CH2Br(79)

    I almost made the same error!
    Yes, don't worry I banged my head on the wall several times for that mistake (without any helmet).

    I thought that they were asking about the possible combinations neglecting any overlaps.
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    - Group 1 and 2 elements have fixed oxidation states right?
    - How are isomers of a molecule identified and differentiated by IR spectroscopy? Is it only by looking at the fingerprint region?
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    Which organic reactions do we need to know the mechanisms for?
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    (Original post by SKK94)
    Group 1 and 2 elements have fixed oxidation states right?
    Mostly, but not always. Eg in NaHS the oxidation number of sodium is -2. I have no idea why though.

    EDIT: Sorry this was a "Read the question" mistake, the question I answered was about sulphur not sodium! No wonder I got it wrong. Then yes assume Na is always +1.
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    Colourless to purple/ pink


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    (Original post by A Peppers)
    Which organic reactions do we need to know the mechanisms for?
    http://www.edexcel.com/migrationdocu...4%20250510.pdf

    go to page 43. or page 41 if you look on the bottom right corner of the actual document.
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    (Original post by adi19956)
    Mostly, but not always. Eg in NaHS the oxidation number of sodium is -2. I have no idea why though.
    Who told you that sulfur is +1 then?

    It depends what the question tells you tbh.
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    Hello does anyone know if we need to know the naming system for halogenoalkane refrigerants (eg R134a) on page 214 in the edexcel textbook?
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    with displacement reactions of halogens with k halides, why can you shake it with an organic solvent? what does it do and why does it happen??
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    why does magnesium react diffrently with steam? do we need to know why? also does anyone know if we need to know about back titrations?- what are they?
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    (Original post by Katy1704)
    Hello does anyone know if we need to know the naming system for halogenoalkane refrigerants (eg R134a) on page 214 in the edexcel textbook?
    No but you will be required to discuss the uses of halogenoalkanes, eg as fire retardants and
    modern refrigerants.
 
 
 
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