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

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    (Original post by harry_maskell)
    4f is wrong- it was because the acid was already in excess so adding more would do nothing.
    Of my understanding of the question, you were using a larger volume of acid with same mass of whatever in a new experiment. So if the acid is in excess and you added the whatever reactant, it will release the same amount of energy, but because you have a larger volume of acid, it will require a greater release of energy to get the same change in temperature to when 25cm3 was used so thats why the change in temperature wasn't as great.
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    (Original post by harry_maskell)
    4f is wrong- it was because the acid was already in excess so adding more would do nothing.
    i said that too!!
    but have no idea if it's right lol
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    what did everyone get for the question on amount of water present in the water of crystallisation question?
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    (Original post by h_wxller1)
    what did everyone get for the question on amount of water present in the water of crystallisation question?
    i got 1.41g but some people i spoke to said it was 0.9??
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    (Original post by h_wxller1)
    i got 1.41g but some people i spoke to said it was 0.9??
    It was 0.9g, I can't remember the exact calculation but you got 0.01 moles x 5 then x by the RFM of water.
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    (Original post by h_wxller1)
    i got 1.41g but some people i spoke to said it was 0.9??
    I got 1.25g! But everyone I spoke to said 0.9g because you had to times/divide by the coefficient or something like that?!
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    The question about the mass of water?
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    (Original post by h_wxller1)
    i got 1.41g but some people i spoke to said it was 0.9??
    I got 0.9


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    what about question 8?
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    (Original post by dance25)
    I got 0.9


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    that was the only one i was unsure of, pretty much everything else i was good on
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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).

    3.g)
    A pair of electrons and nuclei of two atoms. (2)

    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)

    4.g)
    Draw arrow up onto the powder. (1)

    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)
    10 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)

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

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

    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)

    15.a)
    Formula of titanium something must equal to that of the question. (2)

    15.b)
    Structure of titanium - giant metallic, layers of +ve ions surrounded by a sea of delocalised electrons. (2)

    15.c)
    Titanium is conductive as free delocalised electrons don't belong to specific ion hence can quickly transfer charge form -ve to +ve terminal in circuit. (1)

    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)
    What was question 11b? was it the name or the formula of the hydrocarbon?
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    (Original post by exams2)
    What was question 11b? was it the name or the formula of the hydrocarbon?
    Molecular formula.
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    (Original post by HuggettSTS)
    The question about the mass of water?
    wasn't it the moles of water?
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    (Original post by conradliebers)
    Molecular formula.
    shocking that i read such a simple q wrong
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    (Original post by h_wxller1)
    that was the only one i was unsure of, pretty much everything else i was good on
    Same except for the dynamic eq question...


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    (Original post by h_wxller1)
    that was the only one i was unsure of, pretty much everything else i was good on
    Did you bio on Tuesday? How was it?


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    (Original post by h_wxller1)
    i got 1.41g but some people i spoke to said it was 0.9??
    Yep, there was 0.1 moles, 1:5 ratio makes it 0.5 times by the Mr of water which is 18 to make 0.9
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    (Original post by HKHASSAN)
    Effervescence/Fizzing
    Cloudy solution (MAYBE)
    I put that calcium forms an alkaline solution for one othe points, will that get me a mark?
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    What about the question which asked why hydrogen had a low melting and boiling point?

    (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).

    3.g)
    A pair of electrons and nuclei of two atoms. (2)

    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)

    4.g)
    Draw arrow up onto the powder. (1)

    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)
    10 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)

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

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

    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)

    15.a)
    Formula of titanium something must equal to that of the question. (2)

    15.b)
    Structure of titanium - giant metallic, layers of +ve ions surrounded by a sea of delocalised electrons. (2)

    15.c)
    Titanium is conductive as free delocalised electrons don't belong to specific ion hence can quickly transfer charge form -ve to +ve terminal in circuit. (1)

    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)
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    (Original post by fuzi8n137)
    Yep, there was 0.1 moles, 1:5 ratio makes it 0.5 times by the Mr of water which is 18 to make 0.9
    Do you remember how many marks this question was worth?
 
 
 
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