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iGCSE 2012 Chemistry Discussion

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    What did you write for the table about soluble and insoluble products forming? I think I wrote soluble, soluble, insoluble? Is that correct?
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    what do you think will come up on Tuesdays exam?
    According to the spec:
    Moles calculations
    Ionic Compounds (e.g. NaCl)
    Covalent substances (diamonds, graphite)
    Electrolysis
    Ethanol
    Endo/Exothermic reactions
    Polymers, polymerisation
    Contact Process-Sulphuric Acid
    Ionic Equations (half equation at cathode/anode, etc)
    NaOH-making soaps, etc.

    Do you think extraction of Aluminium will come up? How about Haber Process?
    What calculations to look out for?
    Anyone?
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    Hello once again guys. I just went through the specification and i have some questions . If anyone can answer them , i would me more that happy !

    1) According to the specification , we have to know how to draw a simple structure of sodium chloride, showing the positions of the NA+ and CL- ions. How can we do this ?

    2) Also , it says that we have to know a use for diamond and graphite, and support it .
    Can we say that diamond is used to cut stone and concrete, since it is hard , with a high melting and boiling point, and that graphite is used as a dry lubricant, because it is slippery, and its layers can be easily flaked off, since the intermolecular forces of attraction are very weak , and need low energy to be broken down ?
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    (Original post by g_l)
    what do you think will come up on Tuesdays exam?
    According to the spec:
    Moles calculations
    Ionic Compounds (e.g. NaCl)
    Covalent substances (diamonds, graphite)
    Electrolysis
    Ethanol
    Endo/Exothermic reactions
    Polymers, polymerisation
    Contact Process-Sulphuric Acid
    Ionic Equations (half equation at cathode/anode, etc)
    NaOH-making soaps, etc.

    Do you think extraction of Aluminium will come up? How about Haber Process?
    What calculations to look out for?
    Anyone?
    I suggest to have a look at the electrolysis calculations, and perhaps at the titration ones? The extraction of aluminium, as well as iron in the blast furnace might come . Also , check the Haber process, and the contact process. Finally , have a look at the dynamic equilibrium chapter, and giant ionic and giant covalent structures, and end your revision by revising the specification , by placing a tick next to the points that you know, and circle the ones that you need to have a look once more , and you shall be just fine. Good Luck !
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    (Original post by Coco406)
    I don't think it turns reddish-brown because bromine LIQUID is not formed, bromine SOLUTION is formed so it would surely be yellow-orange?

    (Original post by Sub150)
    Where did the water come from for the creation of Bromine water??? If Cl gas is added to a Halogenic soln. it doesn't react to make water?? Besides, you dont need to worry about reddish/brown or yellow brown... Just write browny colour... and yes, that is the test for alkenes
    No Bromine is evolved which DISSOLVES in the water thus making it orange. Brown would be marked wrong. I've checked this with a teacher, accept it; dont hate. :P
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    (Original post by Coco406)
    Bromine water is produced (bromine aq)... not liquid bromine
    If it said bromine (l) then it would be reddish-brown, but it said (aq) and the test for alkenes is that they decolorise yellow-orange bromine water.

    I'm pretty sure that that's right?
    No it was bromine gas in the NaCl solution as chlorine had just displaced bromine. So it's reddish-brown.
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    (Original post by Big-Daddy)
    No it was bromine gas in the NaCl solution as chlorine had just displaced bromine. So it's reddish-brown.
    you wouldnt get the mark if said reddish brown because thats the colour of bromine water, AQUEOUS bromine always has to be orange/yellow. Sorry I've seen it on too many past paper mark schemes 'Orange/Yellow -Reject Red or Brown'
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    (Original post by nithpriya)
    where can you get 2011 igcse grade boundaries for all subjects?
    Hi, I am on my iPod which is why I cant get you a link...

    If you type Edexcel Grade Boundaries and go to their website and then control-f international - you will find the June 2011 grade boundaries (chemistry was 140 out of 180 by the way)

    ^ I checked because I know I lost 12 marks in the last Chem exam!


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    what do you think will come up in the next paper?
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    Help me please
    HBr + NaOH => NaBr + H2O
    Please explain, in terms of ions, why this is a neutralisation reaction.
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    (Original post by g_l)
    Help me please
    HBr + NaOH => NaBr + H2O
    Please explain, in terms of ions, why this is a neutralisation reaction.
    HBR contains H+ ion which is reponsible for the acidity of the solution. NaOH contains the OH- ion which is responsible for the alkalinity of a solution. When the two react, they form water where the concentration of the H+ ions and OH- ions are the same; meaning that the solution is neutral. Therefore it is a neutralization reaction.
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    (Original post by relaxedexams)
    hbr contains h+ ion which is reponsible for the acidity of the solution. Naoh contains the oh- ion which is responsible for the alkalinity of a solution. When the two react, they form water where the concentration of the h+ ions and oh- ions are the same; meaning that the solution is neutral. Therefore it is a neutralization reaction.
    thanks a bunch <3
    Sad thing is in the PastPaper, it is only a 1 mark question
    With 4 lines for writing -.-
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    (Original post by g_l)
    thanks a bunch <3
    Sad thing is in the PastPaper, it is only a 1 mark question
    With 4 lines for writing -.-
    For 1 mark, you can just write that when the reaction takes place, H+ ions and OH- ions react to form water where the concentration of these two ions is the same; making it a neutralization reaction.
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    (Original post by pouloukos)
    That graphite is used as a dry lubricant, because it is slippery, and its layers can be easily flaked off, since the intermolecular forces of attraction are very weak , and need low energy to be broken down ?
    There arent intermolecular attractions in graphite. Graphite is a giant covalant substance. It doesn't have intermolecular forces. If it it, it would have a much lower melting and boiling point! I think you mean the attractions between two layers?
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    (Original post by Relaxedexams)
    There arent intermolecular attractions in graphite. Graphite is a giant covalant substance. It doesn't have intermolecular forces. If it it, it would have a much lower melting and boiling point! I think you mean the attractions between two layers?
    The attraction between the layers are intermolecular attractions. They are very weak. You better revise this again and stop spending time here. Or you can start reading these;
    http://answers.yahoo.com/question/in...2220652AA92Fi8

    http://chemistrybook.hubpages.com/hu...-Dipole-dipole
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    i think paper 2 ought to be easy cuz its only an hour!!
    im tryin my best to get around 50's then its a definite A*!!
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    (Original post by Relaxedexams)
    There arent intermolecular attractions in graphite. Graphite is a giant covalant substance. It doesn't have intermolecular forces. If it it, it would have a much lower melting and boiling point! I think you mean the attractions between two layers?
    What???
    this is wrong! Stop confusing me!
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    Graphite is a giant covalent structure and is an allotrope of carbon. Unlike diamond it if formed in 2D layers and does contain weak intermolecular forces. But as it is a giant covalent structure to sublime it you not only need to bread the weak intermolecular forces but the covalent bonds as well..
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    (Original post by ▀▀▒=(◕ ‿ ◕)=▒r▀▀)
    Graphite is a giant covalent structure and is an allotrope of carbon. Unlike diamond it if formed in 2D layers and does contain weak intermolecular forces. But as it is a giant covalent structure to sublime it you not only need to bread the weak intermolecular forces but the covalent bonds as well..
    Graphite is giant covalent... There is one delocalised electron, hence the conductivity and the lubrication; te attraction between layers is lowered as a result of this. It's not 2d... And I'm not sure if it contains intermolecular forces


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Updated: October 24, 2012
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