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    ...from its elements

    This is what I thought it was 2Mg(s) + O2(g)---> 2MgO(s)

    but the books answer says Mg(s) + 1/2 O2(g)---> MgO(s)

    why have they done that? I really don't understand, please explain

    thank you
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    They are both right; some people like the second as you have less numbers everywhere, and I favour it too. All that matters are that the ratios are the same.

    e.g. 4X + 2Y ---> 2X2Y
    is the same as 2X + Y ---> X2Y
    Is the same as X + 1/2Y ----> 1/2X2Y
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    (Original post by minacolada)
    They are both right; some people like the second as you have less numbers everywhere, and I favour it too. All that matters are that the ratios are the same.

    e.g. 4X + 2Y ---> 2X2Y
    is the same as 2X + Y ---> X2Y
    Is the same as X + 1/2Y ----> 1/2X2Y
    ok thank you, another quick question , do you think I would not get the mark if that was a question in an exam?
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    (Original post by BuuTuu)
    ...from its elements

    This is what I thought it was 2Mg(s) + O2(g)---> 2MgO(s)

    but the books answer says Mg(s) + 1/2 O2(g)---> MgO(s)

    why have they done that? I really don't understand, please explain

    thank you
    Is this to do with the Enthalpy change topic and the 'enthalpy change of formation'?
    If so, remember that it is the formation of ONE mole of a compound, which is made in the second equation.
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    (Original post by BuuTuu)
    ok thank you, another quick question , do you think I would not get the mark if that was a question in an exam?
    Yes, either lowest whole numbers or halves are fine, or at least they were/are for my exam board (Edexcel) Good luck

    Unless as the above said, they were asking for the equation for enthalpy change of formation.
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    Formation will generally be forming one mol of substance.

    OCR didn't allow formation of 2 or more mols for a Enthalpy change definition, so I'd say only the second one is correct.
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    Either is right, personally, I prefer your answer, it means you don't have half moles

    EDIT: oh for gods sake :rolleyes: can't someone have an opinion?
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    As long as the ratios are the same, you should be fine
    So what the book says, what you said and the guy above me said are correct
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    ok, thanks everyone
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    (Original post by EffKayy)
    Is this to do with the Enthalpy change topic and the 'enthalpy change of formation'?
    If so, remember that it is the formation of ONE mole of a compound, which is made in the second equation.
    This.

    (Original post by BuuTuu)
    ...from its elements

    This is what I thought it was 2Mg(s) + O2(g)---> 2MgO(s)

    but the books answer says Mg(s) + 1/2 O2(g)---> MgO(s)

    why have they done that? I really don't understand, please explain

    thank you
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    (Original post by BuuTuu)
    ok, thanks everyone
    Can I ask, was this part of the enthalpy change topic though?
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    (Original post by EffKayy)
    Can I ask, was this part of the enthalpy change topic though?
    no, I have no idea what that is
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    I love how everyone's asking about enthalpy changes when OP's probably just started GCSEs :P
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    (Original post by The Tesco Jinn)
    I love how everyone's asking about enthalpy changes when OP's probably just started GCSEs :P
    lol, nope just started AS
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    Salters by any chance?
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    (Original post by BuuTuu)
    lol, nope just started AS
    Oh, oops, my bad sorry . But yeah same, :five: Well...IB anyway
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    (Original post by The Tesco Jinn)
    Oh, oops, my bad sorry . But yeah same, :five: Well...IB anyway
    lol
 
 
 
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