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    [QUOTE=FemaleBo55;63012439]I was looking for a Chemistry Revision Thread but there were not any so I decided to make one

    Feel free to ask questions regardless of your exam board (because chemistry is chesmitry), and we'll all be happy to answer
    hey question here........
    Compound X changes the colour of warm acidified sodium dichromate(VI) from orange to green.
    1 mol of X reacts with 2mol of HCN in the presence of KCN.
    What could X be?
    A)CH3CH2CH2CHO
    B)CH3COCH2COCH3
    C)H2C=CHCH2CHO
    D)OHCCH2CH2CHO
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    I have ocr 2015 paper and mark scheme for all chemistry units so pm me if u need them people
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    Do you think we need to remember ores like Bauxite or Galena for the actual exam?
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    Oh and I have no idea how chemical equations work. Confundles me every time.
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    (Original post by Glavien)
    Has anyone got the June 2015 AQA unit 4 and unit 5 papers?


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    They're on the website.
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    You know in proton and carbon nmr
    You know those questions they label certain atoms of a molecule A or B and you have to tell the splitting pattern of that atom in a compound.

    How are you supposed to know which 'adjacent' carbon causes the splitting pattern cause it could be different ones on either side. So which adjacent do you use?

    Thanks


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    Help with MAss spectrum
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    (Original post by Bloom77)
    Help with MAss spectrum
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    There will be another peak for Chlorine-37 (+), like the already plotted Chlorine-35 (+) one.

    The x-axis represents mass/charge or m/e ratio - I.e. Mass divided by charge.

    So there will be another peak for 35/2(+) = 17.5

    And another at 37/2(+) = 18.5

    (Also y-axis represents relative abundance - for example could be written as a percentage)

    There is no real way of knowing from the information given what the abundance of Cl (+) is compared to Cl (2+) however you would expect there to be much less of the 2+ ions
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    (Original post by RDB1826)
    There will be another peak for Chlorine-37 (+), like the already plotted Chlorine-35 (+) one.

    The x-axis represents mass/charge or m/e ratio - I.e. Mass divided by charge.

    So there will be another peak for 35/2(+) = 17.5

    And another at 37/2(+) = 18.5

    (Also y-axis represents relative abundance - for example could be written as a percentage)

    There is no real way of knowing from the information given what the abundance of Cl (+) is compared to Cl (2+) however you would expect there to be much less of the 2+ ions
    Thank you, yes I would do what u do. But
    The mark scheme says if there's four peaks, you lose a mark

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    (Original post by Bloom77)
    Thank you, yes I would do what u do. But
    The mark scheme says if there's four peaks, you lose a mark

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    If more than 3 peaks drawn, so if you were to draw 4 then yes I think you'd lose that mark, but 4 in total including the peak already provided is alright I assume
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    (Original post by RDB1826)
    If more than 3 peaks drawn, so if you were to draw 4 then yes I think you'd lose that mark, but 4 in total including the peak already provided is alright I assume
    Oh right, that makes so much sense, thank you!!


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    [QUOTE=alyoan tariq;64901641]
    (Original post by FemaleBo55)
    I was looking for a Chemistry Revision Thread but there were not any so I decided to make one

    Feel free to ask questions regardless of your exam board (because chemistry is chesmitry), and we'll all be happy to answer
    hey question here........
    Compound X changes the colour of warm acidified sodium dichromate(VI) from orange to green.
    1 mol of X reacts with 2mol of HCN in the presence of KCN.
    What could X be?
    A)CH3CH2CH2CHO
    B)CH3COCH2COCH3
    C)H2C=CHCH2CHO
    D)OHCCH2CH2CHO
    so as it reduces chromium from +6 to +3 (orange to green) then the substance must be oxidised so it cannot be a ketone ( not c ) it reacts with HCN and KCN so must be a carbonyl but not ketone so has to be an aldehyde and as one mole of it reacts with two moles of HCN then there must be 2 aldehyde groups so answer is D ?
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    Does anyone know what Kc actually is?
    I'm so confused because i thought it showed where the position of equilibrium was for a reaction but if that is the case then surely it would change with pressure/concentration because these move the position of equilibrium?
    Thanks
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    Do you guys do SALTERS ( past papers for A level Chemistry) ? And are they good enough? 😁


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    Kc comes from Rate Equations of forward and backward reactions. Since Rate constant is only temperature dependant, according to Arrhenius equation so is Kc only temp dependant


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    hello frommmmm JUPITER,

    For ocr salter cHem, am making a grouppppppppppppppp on whatsapp DM me HUMANS... F332,F334, F335 SHALL BE REVIEWED MWAHAHAHAHAHAHAHAHAH
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    Right... I have just over 7 days to get an A in my Chemistry Unit 1 resit, 22 days to get an A in Unit 2 resit.

    Also have 26 days to get an A* in 6CH04 and 34 days to get an A* in 6CH05.
    Should be fun... (already done Unit 1 revision and just starting Unit 2 now .-.)

    Edexcel btw
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    A branched Alkene A was reduced with Hydrogen to form a compound B. Compound B had a composition by mass of C:82.8%, H:17.2% (Mr=58).

    Compound A was reacted with steam with an acid catalyst to produce a mixture of two structural isomers C and D .

    a)Calculate the empirical and molecular formula of a compound B?

    I'd like some advice as to where to start trying to work out how to tackle this question.

    any help is greatly appreciated .

    kind regards to anyone who is helping me
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    (Original post by phspa)
    A branched Alkene A was reduced with Hydrogen to form a compound B. Compound B had a composition by mass of C:82.8%, H:17.2% (Mr=58).

    Compound A was reacted with steam with an acid catalyst to produce a mixture of two structural isomers C and D .

    a)Calculate the empirical and molecular formula of a compound B?

    I'd like some advice as to where to start trying to work out how to tackle this question.

    any help is greatly appreciated .

    kind regards to anyone who is helping me
    Work out the empirical formula of B.
    Then work out the Mr of the empirical formula. If it doesn't match the Mr of 58, it isn't the molecular formula as well. So, multiply the empirical formula's Mr to get the Mr of 58.

    You know how to do the empirical formula right?
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    (Original post by Peppercrunch)
    Work out the empirical formula of B.
    Then work out the Mr of the empirical formula. If it doesn't match the Mr of 58, it isn't the molecular formula as well. So, multiply the empirical formula's Mr to get the Mr of 58.

    You know how to do the empirical formula right?

    Sorry my friend I dont this is the part I'm struggling with . if you could point me in the correct direction I'd be greatly appreciative .

    thanks
 
 
 
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