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    Hi

    I need help with this topic.I will post particular question with which I am struggling now
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    read this question

    the only difference between two spectra is that one has higher transmittance % and other has more absorption.The question says that why student concluded water vapours is most effective.....
    the mark scheme just say that because it has higher absorbance and that what I wrote by looking graphs But I don't have background knowledge that what it mean that if there is more absorption of wavelength why it is more effective.........?
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    The Earth gets heated by radiation from the Sun. This energy is lost through IR. If the atmosphere was 100% transparent to IR, the Earth would cool quickly. BUT some of the frequencies of IR are absorbed by gases in the atmosphere and some of that is re-admitted back towards the ground, i.e. preventing it from escaping.

    Water transmits less (and therefore absorbs more) and over a larger range of frequencies and therefore can trap more heat.
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    (Original post by Pigster)
    The Earth gets heated by radiation from the Sun. This energy is lost through IR. If the atmosphere was 100% transparent to IR, the Earth would cool quickly. BUT some of the frequencies of IR are absorbed by gases in the atmosphere and some of that is re-admitted back towards the ground, i.e. preventing it from escaping.

    Water transmits less (and therefore absorbs more) and over a larger range of frequencies and therefore can trap more heat.

    thanks it makes sense
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    (Original post by Pigster)
    The Earth gets heated by radiation from the Sun. This energy is lost through IR. If the atmosphere was 100% transparent to IR, the Earth would cool quickly. BUT some of the frequencies of IR are absorbed by gases in the atmosphere and some of that is re-admitted back towards the ground, i.e. preventing it from escaping.

    Water transmits less (and therefore absorbs more) and over a larger range of frequencies and therefore can trap more heat.
    can you also help in this question
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    (Original post by Qer)
    can you also help in this question
    Look at the displayed formula of the molecule, identify the functional groups, look up the wavenumbers associated with those functional groups, see if those absorptions are present on the IR spectrum or not.

    If they're not, then that expected functional group is missing.
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    (Original post by Pigster)
    Look at the displayed formula of the molecule, identify the functional groups, look up the wavenumbers associated with those functional groups, see if those absorptions are present on the IR spectrum or not.

    If they're not, then that expected functional group is missing.
    Yeah I do the same
    I wrote that there is no absorption peak of OH BUT mark scheme says no absorption peak of C=O
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    (Original post by Qer)
    Yeah I do the same
    I wrote that there is no absorption peak of OH BUT mark scheme says no absorption peak of C=O
    Alcohol OH peaks are broad at about 3300 - which are present, the U shaped dip on the left.

    C=O peaks are about 1700, which is absent - the line is pretty much at the top, showing pretty much total transmission.

    Transmission means no bond is present to absorb that frequency.
 
 
 

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