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Edexcel Chemistry IGCSE 1C Unofficial Mark Scheme 19th May 2016 Watch

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    (Original post by conradliebers)
    Tell me the questions which I'm missing out - I'll add them in. Please try your best to remember the rough question number.

    1.a)
    Condensation. (1)

    1.b)
    Energy: average ke of particles decreases.
    Arrangement: the intermolecular spaces decrease (as some intermolecular
    forces between particles start to form).
    Movement: particles in liquids slide over each other. (3)

    2.a)
    Filtration. (1)

    2.b)
    Arrow drawn into solvent inside beaker.
    Arrow drawn onto chromatography paper.
    Arrow drawn onto the line on the chromatography paper. (3)

    2.c)
    There are for 4 dyes present in the substance as the original substance
    dissolved into the solvent and 4 dyes were drawn up. (1)

    3.a)
    Hydrogen molecule bonding - two circles that cross over each other and at the
    point of intersection there is a cross and a dot. The circles both have letters H
    inside of them. (1)

    3.b)
    Element in the air - argon. (1)

    3.c)
    Compound present in unpolluted air - H2O (water) or CO2 (carbon dioxide). (1)

    3.d)
    Isotopes are atoms with specific number of neutrons independent to the number of protons that defines the element. (2)

    3.e)
    H1 - 1 proton, 0 neutrons, 1 electron.
    H2 - 1 proton, 1 neutron, 1 electron.
    H3 - 1 proton, 2 neutrons, 1 electron. (3)

    3.f)
    Atom with 3 protons - the diagram with 3 dots.
    Atom in period 3 - the diagram with 15 dots (phosphorous).
    Atom with 15 electrons - diagram with 15 dots (phosphorous).
    Atom which is stable - diagram with 8 dots in outer shell (Neon).

    4.a)
    Simple filling in the temperatures - to 1 dp. (4)

    4.b)
    Max temperature produced by magnesium. (1)

    4.c)
    Ice used to cool down and condense the water vapour. (1)

    4.d)
    Products formed - magnesium chloride and hydrogen (gas). (2)

    4.e) Magnesium can't be used in the reaction using air as it would oxidise to form magnesium oxide. (1)

    4.f)
    Increasing volume of acid to 50cm3 - not so great a rise in temperature as increase in volume of acid means that more energy is required for the same rise in temperature. (2)

    5.a)
    Copper pile turns black because the oxygen in the air reacts with it in a combustion reaction to form Copper oxide (black solid). (2)

    5.b)
    The gas is cooled down before it is measured so that its volume can be recorded at rtp (as the original volume had been measured in these conditions). Heated gases = expansion of volume. (1)

    5.c)
    Why didn't the small heap of copper turn black - because all of the oxygen in the air had been used up in the previous reaction hence no combustion reaction to oxidise copper. (1)

    5.d)
    Percentage of oxygen - 16.6 (recurring) or 16.7%. (2)

    6.a)
    In order of reactivity - Q, R, S, P. (4)

    6.b)
    Graph - draw straight lines of best fit, both lines must intersect. (4)

    6.c)
    Volume used - 12.5 cm3. (1)

    6.d)
    33 degrees celcius. (1)

    7.a)
    Test for presence of water - add to anhydrous copper (II) sulphate, turns white to blue.
    OR add to anhydrous cobalt (II) chloride paper, turns blue to pink. (2)

    7.b)
    Test for purity - physical boiling point test - boils at 100 degrees celsius. (1)

    9.a)
    I2 + Cl2 = 2ICl. (1)

    9.b)
    Two features of equilibrium - rate of forward reaction = rate of reverse reaction and concentration of
    products and reactants are equal. (2)

    9.c)
    The reverse reaction was endothermic because if the forward reaction is exothermic, increasing the temperature decreases the amount of product being formed hence equilibrium shifts to the left where ICl is formed which is brown. (2)

    9.d)
    Test for chloride ions - add nitric acid and silver nitrate, a white precipitate of silver chloride will form. (2)

    10.a)
    Enthalpy change. (1)

    10.b)
    19740 J - something around that. (2)

    10.c)
    Exothermic reaction - transfer of energy from system to surroundings. (1)

    11.a)
    Propane. (1)

    11.b)
    C4H10. (1)

    11.c)
    W, X, Y. (1)

    11.d)
    Empirical formula for Y - CH2. (1)

    11.d)
    A hydrocarbon with a double carbon = carbon covalent bond.
    A hydrocarbon is a organic compound made of hydrogen and carbon only. (3)

    11.e)
    Displayed formula should have only 1 Br atom in it. (1)

    11.f)
    Condition required - UV light. (1)

    12.a)
    Carbon soot was formed in the incomplete combustion due to insufficient oxygen. (1)

    12.b)
    Reason why this affected result - fuel doesn't react fully with air due to insufficient oxygen in incomplete combustion hence not as much energy release. (1)

    12.c)
    Other loss of energy - heat energy lost to surroundings, hence not all transferred to water. (1)

    14.a)
    Fill in the boxes for number of moles in the thermal decomposition. (4)

    13.a)
    Reason for cotton wool - prevent acid from spitting out during reaction. (1)

    14.b)
    Third equation is correct because 2 mole of the original substance forms 1 mole of the product and the table values were 0.08 moles and 0.04 moles. (2)

    16.a)
    Draw graph line - steeper and levels off first but at same level. (2)

    16.c)
    Increase in concentration = increase in particles per unit volume, hence increase in no. of collisions per unit time hence increase in no. of successful collisions per unit time, hence increase in rate of reaction. (3)
    Think you've missed out the questions on covalent bonding and metallic bonding?
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    Also for the one where you have to test for chloride ions, I wrote you need to add silver nitrate, but you do not need to add nitric acid as the HCL is acidic, and a white ppt would form. That would only get me 1 mark right?
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    For 12b could you not say that oxygen would allow the TI to react with it, forming metal oxide ore again (reversing everything)
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    (Original post by jamesj477)
    For the reaction with propane and bromine, do you think I'll get a mark for putting down two bromines on the formula on two different carbon atoms, I know for a fact that this exists - 1,2 dibromopropane. But it said similar to the methane one so I'm not sure?
    The question asked for the displayed formula for one of the PRODUCTS (notice the plural).

    1,2 dibromopropane is one product anyway so it wouldn't have made this.

    Also I think 1,2 dibromopropane is only made from adding bromine water to PROPENE not propane.
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    Hey does anyone know where we were meant to put the arrow for heat on that question with the ice and sideways test tube?
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    (Original post by gameofno)
    anyone else get chromatography wrong? i said 3 dyes instead of 4. ggwp edexcel.
    (Original post by grace_wh)
    yup same, never mind! Seem to remember that it was only 1 mark?

    Haha same; I think it was two marks (one for explain, right?). Either way, even if you said 3 dyes, if you explained roughly the correct thing you should get a mark (and if it was just one mark... oh well)
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    (Original post by jamesj477)
    For the reaction with propane and bromine, do you think I'll get a mark for putting down two bromines on the formula on two different carbon atoms, I know for a fact that this exists - 1,2 dibromopropane. But it said similar to the methane one so I'm not sure?
    i get your struggle. my mistake too
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    (Original post by jamesj477)
    Also for the one where you have to test for chloride ions, I wrote you need to add silver nitrate, but you do not need to add nitric acid as the HCL is acidic, and a white ppt would form. That would only get me 1 mark right?
    Yes.
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    (Original post by Puredbest)
    Hey does anyone know where we were meant to put the arrow for heat on that question with the ice and sideways test tube?
    yeah, you were supposed to put the arrow on the powder in the tube I think
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    (Original post by Puredbest)
    Hey does anyone know where we were meant to put the arrow for heat on that question with the ice and sideways test tube?
    Directly under the copper sulfate, I believe.
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    (Original post by Puredbest)
    Hey does anyone know where we were meant to put the arrow for heat on that question with the ice and sideways test tube?
    Heat upwards onto the powder.
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    (Original post by hazy500)
    Is the answer to 6c not 10 degrees Celcius
    I remember the question was 'what is the maximum rise in temperature' and the temperature started off at 23 degrees and ended at 33, 33-23= 10
    Correct me if im wrong
    I agree - this tripped a lot of people up .

    Since i got 33.1 on the graph i got 10.1 degrees but both are right i presume (hope)

    it definitely said temperature CHANGE
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    (Original post by conradliebers)
    No, because in this halogenation reaction you learn that C3H7Br and HBr is formed.
    would I still get the marks for doing the displayed formula of C3H7Br and writing +HBr as well do you think?
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    (Original post by grace_wh)
    would I still get the marks for doing the displayed formula of C3H7Br and writing +HBr as well do you think?
    Yes
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    (Original post by Puredbest)
    Hey does anyone know where we were meant to put the arrow for heat on that question with the ice and sideways test tube?
    Just realised I did not see this question.
    Pray for me.
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    how many marks for the arrow showing the direction of heat in the experiment? - completely skimmed over that
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    (Original post by HKHASSAN)
    Just realised I did not see this question.
    Pray for me.
    same... only one mark though
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    (Original post by conradliebers)
    Yes.
    why wouldnt that get you 2?
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    (Original post by tmg1999)
    why wouldnt that get you 2?
    I said it would, they'll just ignore the HBr.
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    guys what about the equation of decomposition one? i put equation 3 because a metal carbonate and acid produce a salt, water and carbon dioxide. i think equation 3 was right but not my explanation. it was out of two marks. what did you put?
 
 
 
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