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Help, chemistry c4,c5,c6 10th june 2013 Watch

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    Hey guys, I've got an ocr 21st century triple science exam on Monday and i need tonnes of help with one thing.


    Can anybody give me any help at all about identifying ions? It seems that in most of my mocks I have no idea how to interpret the data.

    Thanks,
    Nathan
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    Ok here you go.

    Metal (positive) ions can be identified two ways.

    1) Use a flame test. Sterilise the end of a nichrome wire with hydrochloric acid and dip into a solid compound that you wish to test. Place the tip under a blue Bunsen flame and observe the flame colour.

    (L)ithium compounds give a crimson colour like (l)ipstick.
    (S)odium compounds give the yellow colour of the (s)un.
    (P)otassium compounds give a lilac colour like lavender in a flower (p)ot.
    Calcium makes your bones strong like bricks. Calcium compounds give a brick red colour.
    (B)arium compounds give a (b)amboo green colour.

    2) Dissolve the compound in distilled water and add a few drops of dilute sodium hydroxide solution. If a precipitate is formed, observe its colour. (This time there is no easy way to remember the colours, just remember them)

    Iron(II), Fe 2+, makes a green precipitate of iron(II) hydroxide.
    Iron(III), Fe 3+, makes a brown precipitate of iron (III) hydroxide.
    Copper(II), Cu 2+, makes a blue precipitate of copper(II) hydroxide.

    Then we need to identify non-metal (negative) ions. There are three tests: identify a carbonate, sulfate or halide.

    1) To identify a carbonate, add a few drops of dilute hydrochloric acid. If you notice fizzing, a gas is being given off. Test with limewater, which should go cloudy if the gas is carbon dioxide. If so, the compound had carbonate ions.

    2) To identify a sulfate, add dilute hydrochloric acid, followed by barium chloride solution. A white precipitate of barium sulfate indicates there are sulfate ions in the compound.

    3) To test for a halide, add nitric acid followed by silver nitrate solution and observe a precipitate colour.

    White - silver chloride (so compound contains chloride ions)
    Cream - silver bromide (so the compound contains bromine ions)
    Yellow - silver iodide (so the compound contains iodide ions).

    Hope that helps a lot!



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    What C module is that from 4,5 or 6?
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    How is everyone feeling about the exam?
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    C5
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    (Original post by champion1)
    Ok here you go.

    Metal (positive) ions can be identified two ways.

    1) Use a flame test. Sterilise the end of a nichrome wire with hydrochloric acid and dip into a solid compound that you wish to test. Place the tip under a blue Bunsen flame and observe the flame colour.

    (L)ithium compounds give a crimson colour like (l)ipstick.
    (S)odium compounds give the yellow colour of the (s)un.
    (P)otassium compounds give a lilac colour like lavender in a flower (p)ot.
    Calcium makes your bones strong like bricks. Calcium compounds give a brick red colour.
    (B)arium compounds give a (b)amboo green colour.

    2) Dissolve the compound in distilled water and add a few drops of dilute sodium hydroxide solution. If a precipitate is formed, observe its colour. (This time there is no easy way to remember the colours, just remember them)

    Iron(II), Fe 2+, makes a green precipitate of iron(II) hydroxide.
    Iron(III), Fe 3+, makes a brown precipitate of iron (III) hydroxide.
    Copper(II), Cu 2+, makes a blue precipitate of copper(II) hydroxide.

    Then we need to identify non-metal (negative) ions. There are three tests: identify a carbonate, sulfate or halide.

    1) To identify a carbonate, add a few drops of dilute hydrochloric acid. If you notice fizzing, a gas is being given off. Test with limewater, which should go cloudy if the gas is carbon dioxide. If so, the compound had carbonate ions.

    2) To identify a sulfate, add dilute hydrochloric acid, followed by barium chloride solution. A white precipitate of barium sulfate indicates there are sulfate ions in the compound.

    3) To test for a halide, add nitric acid followed by silver nitrate solution and observe a precipitate colour.

    White - silver chloride (so compound contains chloride ions)
    Cream - silver bromide (so the compound contains bromine ions)
    Yellow - silver iodide (so the compound contains iodide ions).

    Hope that helps a lot!



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    Thank you so much!
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    (Original post by MissC123)
    How is everyone feeling about the exam?
    Confident I guess, you?
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    They give you the ion tests in the exam, no need to learn them by heart
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    What about the flame test?
    P.S this helped me understand it
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    possible 6 marks-

    Just revise everything! I think that they might ask us 6 marks on-
    -Rate of reactions/using different methods to determine it
    -The periodic table(HALOGENS vs ALKALI METALS)
    -Which ore is the most economically viable to extract out of a table.
    -Which metal is the most appropriate for this job?
    -Exo/Endo reactions
    -Correlation and cause and a random topic(THE DOGGY ONE)
    -How can a factory owner make their yeild larger/improve efficiency...
    -The different ways of extracting an ore-(ELECTROLYSIS/REDUCTION)

    One of these is bound to come up!If not then we have all flopped the test like jan p4p5p6
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    (Original post by TAPTUT)
    possible 6 marks-

    Just revise everything! I think that they might ask us 6 marks on-
    -Rate of reactions/using different methods to determine it
    -The periodic table(HALOGENS vs ALKALI METALS)
    -Which ore is the most economically viable to extract out of a table.
    -Which metal is the most appropriate for this job?
    -Exo/Endo reactions
    -Correlation and cause and a random topic(THE DOGGY ONE)
    -How can a factory owner make their yeild larger/improve efficiency...
    -The different ways of extracting an ore-(ELECTROLYSIS/REDUCTION)

    One of these is bound to come up!If not then we have all flopped the test like jan p4p5p6
    Have you wrote answers to these by any chance?
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    Does anyone have the link for the c4 c5 c6 January 2013 paper?
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    I remember the p4, p5, p6....it was so hard but somehow i managed to get 100 wtf.
    Last year for c4c5c6 you needed 37 for an a i think...
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    How did everyone find it?
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    (Original post by azzawazza)
    How did everyone find it?
    I thought it was relatively however i thought the last 6 marker was challenging
    conpared to the past papers i expected harder
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    Pretty easy really I found. Just a slight blip in that I initially thought that if the energy of the products went down, it was an endothermic reaction, yet it's actually the opposite... So my answer was really messy as I had to change all the wording. (last 6 marker)
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    (Original post by jjpneed)
    Pretty easy really I found. Just a slight blip in that I initially thought that if the energy of the products went down, it was an endothermic reaction, yet it's actually the opposite... So my answer was really messy as I had to change all the wording. (last 6 marker)
    ahaha lol that doesn't matter.I think the six marks were great.They literally required no knowledge.I think i dropped odd 1 or 2 markers but overall i found it quite easy.I think grade boundaries are gona be 43/44 for an a*.
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    (Original post by Chocolatecake123)
    Have you wrote answers to these by any chance?
    NO BUT ENDO/EXO CAME UP! I'm amazing at predicting
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    (Original post by TAPTUT)
    ahaha lol that doesn't matter.I think the six marks were great.They literally required no knowledge.I think i dropped odd 1 or 2 markers but overall i found it quite easy.I think grade boundaries are gona be 43/44 for an a*.
    I know yeah. The first two pages were surprisingly easy, and the maths was pretty hard to get wrong if you had common sense. The first 6 marker was quite strange I thought, but it was literally just copying information
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    What did you guys get for the concentration question I got 0.4 and then 400 and what about the mass in mgs04? or whatever it was. It was relatively easy but that means the boundaries will go up which isn't the best
 
 
 
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