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iGCSE 2012 Chemistry Discussion

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    (Original post by g_l)
    Here is the triple spec., the bits in bold of the specification *NOT SAYING THAT YOU SHOULD NOT REVISE EVERYTHING ELSE, JUST SAYING TOPICS TO PAY MORE ATTENTION TO. haters quit yo' hatin' *
    Section 1: Principles of chemistry
    d) Relative formula masses and molar volumes of gases
    1.18 understand the term mole as the Avogadro number of particles (atoms, molecules, formulae, ions or electrons) in a substance
    1.20 understand the term molar volume of a gas and use its values (24 dm3 and 24,000 cm3) at room temperature and pressure (rtp) in calculations.

    e) Chemical formulae and chemical equations
    1.26 calculate percentage yield

    f) Ionic compounds
    1.35 understand the relationship between ionic charge and the melting point and boiling point of an ionic compound
    1.36 describe an ionic crystal as a giant three-dimensional lattice structure held together by the attraction between oppositely charged ions
    1.37 draw a diagram to represent the positions of the ions in a crystal of sodium chloride.

    g) Covalent substances
    1.44 draw diagrams representing the positions of the atoms in diamond and graphite
    1.45 explain how the uses of diamond and graphite depend on their structures, limited to graphite as a lubricant and diamond in cutting.

    i) Electrolysis
    1.54 describe experiments to investigate electrolysis, using inert electrodes, of aqueous solutions such as sodium chloride, copper(II) sulfate and dilute sulfuric acid and predict the products
    1.56 recall that one faraday represents one mole of electrons
    1.57 calculate the amounts of the products of the electrolysis of molten salts and aqueous solutions.

    Section 2: Chemistry of the elements

    b) Group 1 elements — lithium, sodium and potassium
    2.8 explain the relative reactivities of the elements in Group 1 in terms of distance between the outer electrons and the nucleus.

    Section 3: Organic chemistry

    d) Ethanol

    3.9 describe the manufacture of ethanol by passing ethene and steam over a phosphoric acid catalyst at a temperature of about 300°C and a pressure of about 60–70 atm
    3.10 describe the manufacture of ethanol by the fermentation of sugars, for example glucose, at a temperature of about 30°C
    3.11 evaluate the factors relevant to the choice of method used in the manufacture of ethanol, for example the relative availability of sugar cane and crude oil
    3.12 describe the dehydration of ethanol to ethene, using aluminium oxide.
    Section 4: Physical chemistry
    b) Energetics
    4.12 calculate molar enthalpy change from heat energy change
    4.16 use average bond energies to calculate the enthalpy change during a
    simple chemical reaction.

    Section 5: Chemistry in industry
    c) Synthetic polymers
    5.16 draw the repeat unit of addition polymers, including poly(ethene), poly(propene) and poly(chloroethene)
    5.18 describe some uses for polymers, including poly(ethene), poly(propene) and poly(chloroethene)
    5.20 understand that some polymers, such as nylon, form by a different process called condensation polymerisation
    5.21 understand that condensation polymerisation produces a small molecule, such as water, as well as the polymer.

    d) The industrial manufacture of chemicals

    5.26 recall the raw materials used in the manufacture of sulfuric acid
    5.27 describe the manufacture of sulfuric acid by the contact process, including the essential conditions:
    i a temperature of about 450°C
    ii a pressure of about 2 atmospheres
    iii a vanadium(V) oxide catalyst
    5.28 describe the use of sulfuric acid in the manufacture of detergents, fertilisers and paints
    5.29 describe the manufacture of sodium hydroxide and chlorine by the electrolysis of concentrated sodium chloride solution (brine) in a diaphragm cell
    5.30 write ionic half-equations for the reactions at the electrodes in the diaphragm cell
    5.31 describe important uses of sodium hydroxide, including the manufacture of bleach, paper and soap; and of chlorine, including sterilising water supplies and in the manufacture of bleach and hydrochloric acid.

    And that's it people.... remember, these are just the triple statements and they may test you on things on the double statement that they didn't test you on Monday. GOOD LUCK.
    *phew that took long*

    Hey, doesnt it say on the specification that this is the only stuff we need to know, do we seriously need to revise for all the dual stuff again!
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    (Original post by kinglj81)
    Hey, doesnt it say on the specification that this is the only stuff we need to know, do we seriously need to revise for all the dual stuff again!
    If you don't know it yet...


    This was posted from The Student Room's iPhone/iPad App and also from an iPhone but not an iPad and why isn't it an iPod app?
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    (Original post by eebootwo)
    If you don't know it yet...


    This was posted from The Student Room's iPhone/iPad App and also from an iPhone but not an iPad and why isn't it an iPod app?
    i want to rate your post but i cannot
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    (Original post by Big-Daddy)
    It was an oxygen atom, not silicon. Each of those atoms was bonded to 2 others, so it can only have been oxygen - silicon would have had 4.

    For the record, I put ionic as well. Hopefully I didn't lose many other marks ...

    BTW the solution started colourless, but I'm not sure what colour it turned. I put reddish-brown.
    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?
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    Anybody have the question sheet and answers? thanks
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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?
    How is it a soln of bromine??? If NaBR is displaced by pure Cl, than pure Br is produced. At RTP, bromine is liquid so......
    And im pretty sure you ignore the .XH20 in the equation as you say its (aq) anyway
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    how much did you get for the number of H20 in condensation question(last ques i think)?

    is 1/7 right??
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    (Original post by Sub150)
    How is it a soln of bromine??? If NaBR is displaced by pure Cl, than pure Br is produced. At RTP, bromine is liquid so......
    And im pretty sure you ignore the .XH20 in the equation as you say its (aq) anyway
    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?
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    (Original post by nithpriya)
    how much did you get for the number of H20 in condensation question(last ques i think)?

    is 1/7 right??
    No. Its 7.
    I remember that the moles of water was 0.03, and the moles of the other substance was 0.21. So to make it even there needed to be 7 water molecules (0.03*7=0.21) if you got 1/7, you prb did it the other way around, or measured the wrong moles.
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    (Original post by nithpriya)
    how much did you get for the number of H20 in condensation question(last ques i think)?

    is 1/7 right??
    Is that the water of crystallisation?
    I got x as being 7
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    where can you get 2011 igcse grade boundaries for all subjects?
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    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
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    (Original post by Coco406)
    Is that the water of crystallisation?
    I got x as being 7
    Yeah.
    I thought the answer was stupid when it came upside down.
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    (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
    I just went with the state signs haha- (aq) would imply an orange and (l) a reddish-brown but either way it's only 1 mark
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    Yes, but thinking about what did and did not go wrong on past papers is a very effective way of procrastination; you can convince yourself that you are working, but you really are not, which is why it is very addictive :/
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    (Original post by Sub150)
    Yes, but thinking about what did and did not go wrong on past papers is a very effective way of procrastination; you can convince yourself that you are working, but you really are not, which is why it is very addictive :/
    Haha completely agree with you! The amount of time I have wasted in doing so...
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    (Original post by nithpriya)
    Yeah.
    I thought the answer was stupid when it came upside down.
    I wouldn't worry! You'll definitely get working marks
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    What did you guys get for the question about thermochemistry? It was also something about therlsomerism and tertiary alcohols being non-reacitve?
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    (Original post by Coco406)
    I wouldn't worry! You'll definitely get working marks
    hope so! cuz i think chemistry was the easiest!
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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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Updated: October 24, 2012
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