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AQA GCSE Chemistry C2/C3 May 15th 2014 watch

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    Calculate the percentage yield if 9.0g MgSO4 was made from 4.0g MgO.

    I knew how to do this before, but I've spent 30 minutes trying to work this out? CHESWDCKJNEWLksmdc.m sdkj
    The answer is 75%. Please explain. -_-
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    (Original post by rm_27)
    Calculate the percentage yield if 9.0g MgSO4 was made from 4.0g MgO.

    I knew how to do this before, but I've spent 30 minutes trying to work this out? CHESWDCKJNEWLksmdc.m sdkj
    The answer is 75%. Please explain. -_-
    What's the reaction equation?

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    (Original post by majmuh24)
    What's the reaction equation?

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    It's not given. I think they assume we should know it.
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    (Original post by rm_27)
    It's not given. I think they assume we should know it.
    I assume it's MgO + SO3 ==> MgSO4 then (was there something to do with acid rain?)

    1 mol. Mg ==> 1 mol. MgSO4

    RMM magnesium is 24
    RMM oxygen is 32
    RMM sulfur is 16

    Using this, we get that

    56g MgO ==> 168g MgSO4

    Dividing by 14 gives

    4g MgO ==> 12g MgSO4

    And the problem is easy from there

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    (Original post by rm_27)
    It's not given. I think they assume we should know it.
    Sorry but I don't know >.<
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    (Original post by Silver-wind)
    Come at me brah
    Please give me any tips you have
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    Oxygen is 16...sulfur 32 :P
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    okay so basically the relative atomic masses first
    oxygen =16
    sulfur=32
    magnesium=24

    so mgo---> mgS04

    mgo=24+16=40
    mgso4 = 24=16=(16x3)=120

    so its 40:120
    which can be cancelled to 4:12
    so 12g of mgso4 should be produced
    actual/theoretical X 100 to get the percentage yield right
    so 9/12 = 0.75x100 = 75% not that hard theyre just trying to be confusing!
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    Anyone got any thoughts on what the 6 marker will be on C2? Based on previous years etc?
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    (Original post by chronicmusic)
    Please give me any tips you have
    Got a feeling about whats going to come up in the exam, it came to me and the more I think about it the more it makes sence!
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    (Original post by Kevin Paul Beale)
    Got a feeling about whats going to come up in the exam, it came to me and the more I think about it the more it makes sence!
    and whats that then
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    Do you guys think anything on nano particles will come up? Or precipitation reactions? Titration was last year, but could it be repeated?
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    (Original post by Kevin Paul Beale)
    Got a feeling about whats going to come up in the exam, it came to me and the more I think about it the more it makes sence!
    Have you got the Folens revision guide? It's really good for downloading powerpoints and claiming they are your own work that took you 12 hours!
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    Predicted 6 markers for C2:

    I believe there will be 2 six markers, the first on nanoscience (uses and what nanoparticles are) and the other on polymers (platics, thermosoftening/setting, exothermic/endothermic). Only one will be a QWC though so you'll need about 4/5 points each
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    (Original post by chronicmusic)
    Predicted 6 markers for C2:

    I believe there will be 2 six markers, the first on nanoscience (uses and what nanoparticles are) and the other on polymers (platics, thermosoftening/setting, exothermic/endothermic). Only one will be a QWC though so you'll need about 4/5 points each
    nanoscience has loads of points, polymers I can think of maybe 2/3 for each
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    (Original post by voxdock)
    nanoscience has loads of points, polymers I can think of maybe 2/3 for each
    Yeah true, would you mind listing your points to help me/other people out?
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    Can someone please explain to me how to make insoluble salts? I tried CGP and my-gcsescience but I still can't understand. :confused:
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    (Original post by chronicmusic)
    Yeah true, would you mind listing your points to help me/other people out?
    nanoparticles-1-100nm in length, inc fullerenes
    nano science: fullerenes
    huge SA:vol so industrial catalysts
    nanomedicine-absorbtion by body
    cosmetics
    buildings
    strong covalent bonds, so strong
    conductrors-computer parts
    sun cream
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    My teacher has a strong feeeling that electrolysis is going to be on the c2 exam for the 6 marks...im really worried an unprepared for this exam!

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    (Original post by kkomde)
    Can someone please explain to me how to make insoluble salts? I tried CGP and my-gcsescience but I still can't understand. :confused:
    I will use silver chloride as an example. Silver chloride is insoluble. You need a soluble silver salt and a soluble chloride salt to make it. Silver nitrate and sodium chloride are both soluble. When you mix their solutions together, you make soluble sodium nitrate and insoluble silver chloride:

    • silver nitrate + sodium chloride → sodium nitrate + silver chloride
    • AgNO3(aq) + NaCl(aq) → NaNO3(aq) +AgCl(s)

    The silver chloride appears as tiny particles suspended in the reaction mixture - it forms a precipitate. The precipitate can be filtered, washed with water on the filter paper, and then dried in an oven.
    Remember: if you want to make an insoluble salt XY, mixing X nitrate with sodium Y will always work. In the example above, X is silver and Y is chloride.
 
 
 

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