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    (Original post by sophiegashman)
    Sorry I was having a totally stupid moment and using the Mr of Ammonium instead of Ammonia! Thanks for the help though A-levels are most definitely frazzling my brain!
    I know, the volumes of material you have to remember and apply can fog your mind at times! I've done that sort of thing before. If you can't concentrate properly. I usually stop and take a break. Clear your head. You'll only learn with a clear mind.
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    (Original post by ozzie2)
    What I do is find the amount of electrons on the outer shell of the bonding atom.
    Then I work out the electrons that the bonding atom wants - eg chlorine wants 1 (as it will be sharing the same as the electron it wants in the bond if you get me)
    Then I add these both together to get the total electrons and divide by 2 as there are 2 electrons in a pair. You can work out how many lone pairs after taking away the shared electrons in the compound

    Eg NH3 : So nitrogen has 5 outer electrons. Hydrogen wants a total of 3 electrons.
    Now add these both together and there are 8 electrons so a total of 4 bonds. As there are 3 hydrogens there are 3 bonds with atoms so lose 6 electrons (2 electrons per pair) and you are left with 2 electrons, which are a lone pair as it doesn't bond with any atoms.

    Hope this helps, dunno if I even answered the question properly haha
    Oh no I do that as well haha
    I was asking something a little bit different but thanks for trying to help
    I used an A2 organic compound but it's an AS concept so thought I would post it on here.
    What about ethanol for example? I don't think our method works for larger compounds because it'll be 6,1,4?
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    Hi guys, just a practical question:

    Is there a special way to print Edexcel Chemistry (and all Edexcel science papers for that matter) off?? It seems as though when I try to print it off, there's a white border right around the main page, which is useless and just makes the pages difficult to read because they are made smaller. My school seems to be able to get the papers printed without issue.

    Hioefully this is easily resolvable - I just want the useful part of the paper to take up more of the page
    For example, although this paper appears full page, in reality when I print it off there's a massive plain white boarder to all sides of the black barcodes/rectangles. Anyone able to help?!!
    http://qualifications.pearson.com/content/dam/pdf/A%20Level/Chemistry/2013/Exam%20materials/6CH01_01_que_20110113.pdf


    Thanks!
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    (Original post by gabby07)
    x
    Got the same problem
    At home when I print on A4 double sided I have no problem
    But at school when i get to print out on A3 as booklet style it becomes small to almost size of A4 booklet style (which is A5 size a page)
    I have tried to scale it up but it doesn't work ::dontknow:


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    can someone explain this to me please? (aqa board)
    In terms of atomic structure, explain why the van der Waals’ forces in liquid argon arevery weak.
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    (Original post by blueberry389)
    can someone explain this to me please? (aqa board)
    In terms of atomic structure, explain why the van der Waals’ forces in liquid argon arevery weak.
    As you go across a period, the amount of protons increases. This increases the attraction between the outer shell electrons and the nucleus, which draws in the outer shell electrons more, making the atom smaller. The smaller the atom, the weaker the Van Der Waals forces of attraction.
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    Hi could someone explain how to find the answer to this question/questions like this? Is it something to do with equilibria favouring fwd reaction due to the fact you added OH ions (and it wanted to revert back by adding more H ions? And because the fwd reaction causes yellow colour, the solution just remains yellow? Or something else




    Thanks

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    (Original post by gabby07)
    Hi could someone explain how to find the answer to this question/questions like this? Is it something to do with equilibria favouring fwd reaction due to the fact you added OH ions (and it wanted to revert back by adding more H ions? And because the fwd reaction causes yellow colour, the solution just remains yellow? Or something else




    Thanks

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    The OH ions from the sodium hydroxide will react with the H+ on the right hand side to form H20 and therefore the H+ ions from the equilibrium is removed. Can you now see which direction the equilibrium will shift to compensate?
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    (Original post by James A)
    The OH ions from the sodium hydroxide will react with the H+ on the right hand side to form H20 and therefore the H+ ions from the equilibrium is removed. Can you now see which direction the equilibrium will shift to compensate?
    Ah yes. Thanks for the explanation
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    How was the Unit 3 exam folks??
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    for the unit 3 exam are you guys gonna revise ever single thing in group 2 and group 7? cuz theres a lot, should i just revise the bits related to the practical we did cuz i can remember the things we added
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    Could you guys help me out on structure & bonding?

    I just don't understand how to work out the final shape of the molecule l, like do you guys have any tips? xx

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    (Original post by Heretohelp!)
    Could you guys help me out on structure & bonding?

    I just don't understand how to work out the final shape of the molecule l, like do you guys have any tips? xx

    Posted from TSR Mobile
    Look at the number of bonded pairs: lone pairs in the molecule. Lone pairs always repel more that bonded pairs. There's a rule that it's about 2.5 degrees difference in repulsion per lone pair added (but there's other factors involved also. So don't worry about that too much).

    There is some memorisation involved (in OCR anyway). Use your notes, resources etc

    E.g H20, because oxygen has 6 electrons in it's outer shell. Therefore there will be 2 bonded pairs and 2 lone pairs in tge molecule because 2 of oxygen's electrons are used in 1 covalent bond (with a hydrogen atom) each. Lps repel more than bps, therefore the bond angle is 104.5 degrees with a shape which is described as ''angular'' or ''v-shaped''. Learn the shapes and bond angle rules.
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    (Original post by becauseitslaura)
    As you go across a period, the amount of protons increases. This increases the attraction between the outer shell electrons and the nucleus, which draws in the outer shell electrons more, making the atom smaller. The smaller the atom, the weaker the Van Der Waals forces of attraction.
    I would also be inclined to mention that it exists as a single atom therefore is a smaller molecule and has lower van der waals forces
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    (Original post by Heretohelp!)
    Could you guys help me out on structure & bonding?

    I just don't understand how to work out the final shape of the molecule l, like do you guys have any tips? xx

    Posted from TSR Mobile
    This helps . This is how I do it..
    So for example.. BCl3
    I would find the amount of e- in central atoms outer shell in this case B (group 3 so 3)
    B = 3e-
    3Cl e- = (3+3 = 6e- /2 so 3 electron pairs and 3 bonding pairs, no lone pairs
    if you learn the table you'll know it's trigonal planar
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    Is there an equation or formula that we could use to work out half lives because I'm really struggling to it work out especially when you are not given intial amount of the radioisotope and what is left over
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    (Original post by A84)
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    (Original post by Georgiam247)
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    (Original post by TARS)
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    (Original post by Cherry82)
    x
    I'm kinda replying a bit late but you guys gave me really good advice. I'm actually doing the full alevels here biology, chemistry and maths this yr plus as physics. I've been off tsr and managed to get AS + half A2 maths, AS biology and a little bit of chemistry and physics done this week (learnt and understood, did some practice questions on topics as I learnt them, I also plan to do the papers real soon). The splitting into chapters and topics technique makes it easier to learn the stuff and seems less overwhelming. Thanks so much.

    btw what's georgiam247, what's LTM?
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    (Original post by samwillettsxxx)
    This helps . This is how I do it..
    So for example.. BCl3
    I would find the amount of e- in central atoms outer shell in this case B (group 3 so 3)
    B = 3e-
    3Cl e- = (3+3 = 6e- /2 so 3 electron pairs and 3 bonding pairs, no lone pairs
    if you learn the table you'll know it's trigonal planar
    Yeah I've been told how to do this method but always get stuck. Thanks for replying though :top:

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    (Original post by jadys10)
    I'm kinda replying a bit late but you guys gave me really good advice. I'm actually doing the full alevels here biology, chemistry and maths this yr plus as physics. I've been off tsr and managed to get AS + half A2 maths, AS biology and a little bit of chemistry and physics done this week (learnt and understood, did some practice questions on topics as I learnt them, I also plan to do the papers real soon). The splitting into chapters and topics technique makes it easier to learn the stuff and seems less overwhelming. Thanks so much.

    btw what's georgiam247, what's LTM?
    Ur much welcome. always message if u need any further help I do AS bio chem and phy.
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    need help in gce paper unit 1 chemistry question 16 b (ii) which is Suggest how you would mix the acid and the coral to ensure that no carbn dioxide escaped from apparatus... ive found an old TSR thread with various answers.. does this look good. what is the "perfect answer"??

    From old TSR thread:

    Stick coral to a bung half fill test tube with acid put bung into test tube shake or flip the other way up so they come into contact In the sealed test tube
 
 
 
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