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Edexcel - Chemistry Unit 2 - 4 June 2013 Watch

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    State two things that you would see when anhydrous calcium nitrate is heated.
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    (Original post by posthumus)
    I guess alkenes have a very low boiling temperature, which makes sense !

    So does anyone have an image of what the apparatus should look like ? I know geor posted one yesterday

    Also is Beryllium the only one which has BeO layer, hence it can't react with water ? If not, then why is it so unreactive
    May 2010 Unit -1 Question # 18a)iii)

    Instead of heating dodecane, you heat a mixture of 2-chlorobutane and alcoholic potassium hydroxide soaked in wool. Aluminium oxide is optional.
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    (Original post by posthumus)
    Yup stick to two !!! It's four in solid form (crystals).
    Can you please explain why this is? Is it something to do with the number of long pairs on the Oxygen atom or is it the fact it has two Hydrogen atoms? The MS also says HF can only form 1 hydrogen bond per molecule, so I'm guessing it's the latter reason.

    Thanks.
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    (Original post by GCSE-help)
    Guys in the Jan 2012 MS it says Water can form 2 Hydrogen bonds per molecule, but some guys on here seem to think it's four?
    Its four, two for the Lone pairs on the oxygen and one per hydrogen, hence why H20 has a much higher boiling point than H-F which only forms two hydrogen bonds per molecule
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    (Original post by airheadbuster)
    May 2010 Unit -1 Question # 18a)iii)

    Instead of heating dodecane, you heat a mixture of 2-chlorobutane and alcoholic potassium hydroxide soaked in wool. Aluminium oxide is optional.
    Okay thanks, but do you have an image of what the apparatus looks like ?


    (Original post by Linked)
    State two things that you would see when anhydrous calcium nitrate is heated.
    Brown fumes of NO2 for sure ! Possibly bubbles of Oxygen gas. Or if CaO has a particular colour, not sure
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    (Original post by posthumus)
    Okay thanks, but do you have an image of what the apparatus looks like ?




    Brown fumes of NO2 for sure ! Possibly bubbles of Oxygen gas. Or if CaO has a particular colour, not sure
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    (Original post by posthumus)
    Yup stick to two !!! It's four in solid form (crystals).
    Can you please explain why this is? Is it something to do with the number of long pairs on the Oxygen atom or is it the fact it has two Hydrogen atoms? The MS also says HF can only form 1 hydrogen bond per molecule, so I'm guessing it's the latter reason.

    Thanks.
    (Original post by bhowland1994)
    Its four, two for the Lone pairs on the oxygen and one per hydrogen, hence why H20 has a much higher boiling point than H-F which only forms two hydrogen bonds per molecule
    Well the mark scheme clearly says two :/
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    does anyone want to revise ??
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    (Original post by posthumus)
    Okay thanks, but do you have an image of what the apparatus looks like ?




    Brown fumes of NO2 for sure ! Possibly bubbles of Oxygen gas. Or if CaO has a particular colour, not sure
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    Here's another better one.

    @GCSE, there are two hydrogen in a molecule of water. So, there will be two hydrogen bonding per molecule.
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    (Original post by GCSE-help)
    Guys in the Jan 2012 MS it says Water can form 2 Hydrogen bonds per molecule, but some guys on here seem to think it's four?
    One water molecule will form 2 hydrogen bonds due to the 2 lone pairs.

    However, the 2 hydrogens can be involved in hydrogen bonds formed by other molecules, giving the appearance of 4 hydrogen bonds around the water molecule.

    So one molecule can form 2 hydrogen bonds, but can be involved in up to 2 more.

    EDIT: Not sure if it's because of the hydrogens or the lone pairs, but that's the basic idea anyway (forms 2, is involved in 2)
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    (Original post by GCSE-help)
    Can you please explain why this is? Is it something to do with the number of long pairs on the Oxygen atom or is it the fact it has two Hydrogen atoms? The MS also says HF can only form 1 hydrogen bond per molecule, so I'm guessing it's the latter reason.

    Thanks.


    Well the mark scheme clearly says two :/
    Then we have to go with what the MS says then ..... but the internet disagrees :P http://wiki.answers.com/Q/What_is_th...ecule_can_form
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    (Original post by bhowland1994)
    Then we have to go with what the MS says then ..... but the internet disagrees :P http://wiki.answers.com/Q/What_is_th...ecule_can_form
    Don't look for the answers on the internet now. It will only confuse you.
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    (Original post by airheadbuster)
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    Here's another better one.

    @GCSE, there are two hydrogen in a molecule of water. So, there will be two hydrogen bonding per molecule.
    SO all the alkenes produced in this reaction are gases ?
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    (Original post by Gnome :))
    One water molecule will form 2 hydrogen bonds due to the 2 lone pairs.

    However, the 2 hydrogens can be involved in hydrogen bonds formed by other molecules, giving the appearance of 4 hydrogen bonds around the water molecule.

    So one molecule can form 2 hydrogen bonds, but can be involved in up to 2 more.
    This makes sense !!!! THANK YOU
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    (Original post by airheadbuster)
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    (Original post by airheadbuster)
    Name:  2.png
Views: 191
Size:  27.8 KB

    Here's another better one.

    @GCSE, there are two hydrogen in a molecule of water. So, there will be two hydrogen bonding per molecule.
    Thank you very much I think I like the second one better !

    (Original post by GCSE-help)
    Can you please explain why this is? Is it something to do with the number of long pairs on the Oxygen atom or is it the fact it has two Hydrogen atoms? The MS also says HF can only form 1 hydrogen bond per molecule, so I'm guessing it's the latter reason.
    I just read it somewhere in the book in all honesty. But theoretically it should have 4, but in solution due to reasons such as steric hinderance I'm guessing there can only be 2. Just think of each appropriate bond pair as being able to produce 1 hydrogen bond. There are 2 O-H bonds, therefore 2 hydrogen bonds are possible. Only 1 H-F, therefore 1 hydrogen bond. Now NH3.... 3 hydrogen bonds?? Hmmm I'll need to check that one
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    (Original post by DrTK278)
    SO all the alkenes produced in this reaction are gases ?
    But-1-ene is a gas at room temperature.
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    (Original post by airheadbuster)
    Don't look for the answers on the internet now. It will only confuse you.
    I know, i was wrong anyway i didnt realise the difference between the word forms and contains .. haha #head slap
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    carry out experiments to study the solubility of simple molecules
    in different solvents - CAN ANYONE GIVE ME ANY EXAMPLES OF THESE? PLS!
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    (Original post by airheadbuster)
    Name:  2.png
Views: 191
Size:  27.8 KB

    Here's another better one.

    @GCSE, there are two hydrogen in a molecule of water. So, there will be two hydrogen bonding per molecule.
    Hi, what does the aluminum oxide do in the above reaction?

    And does ammonia only form 1 hydrogen bond per molecule as it has one lone pair of e- per molecule?
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    A short question : Why does H20 have a higher boiling point than : HF, NH3 , and CH4 ?

    Thanks
 
 
 
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