OCR Chemistry A 2016 unofficial mark scheme 27/05/16

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    (Original post by RedRosesBloom)
    Does anyone remember the second multiple choice question? I'm pretty sure I got a B in that but on this thread people seem to have gotten a C/D?
    https://twitter.com/ChemistryALevel
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    (Original post by ronnydandam)
    This guy is a teacher and will do the whole paper and post the mark scheme https://twitter.com/ChemistryALevel
    Not sure about some of these...
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    (Original post by tizzaclaire98)
    Not sure about some of these...
    Yh some of them don't seem right, but most are correct. At least its something
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    (Original post by tizzaclaire98)
    Not sure about some of these...
    That's what I was thinking
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    (Original post by tamoni4)
    You cannot use Br2 because you will make a dihaloalkane and you cannot make an alcohol from dihaloalkane. You had to use HBr to make haloalkane and then NaOH to make alcohol.
    It was a diol though
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    (Original post by tamoni4)
    You cannot use Br2 because you will make a dihaloalkane and you cannot make an alcohol from dihaloalkane. You had to use HBr to make haloalkane and then NaOH to make alcohol.
    There were 2 OH groups though so you had to use Br2
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    Thanks for the marks scheme really appreciate can I just ask if possible could you update with what the question was if possible, obviously multiple choice may not be possible but for the others could you say what the question was
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    Oh **** it's ammonium sulfide!!!! not sulphate.
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    My answers to multiple choice BCDACBBDABDBBCDDDBBD
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    (Original post by tom2121)
    Thanks for the marks scheme really appreciate can I just ask if possible could you update with what the question was if possible, obviously multiple choice may not be possible but for the others could you say what the question was
    Of course, however you know that there are pictures of the paper on Twitter now? @ChemistryALevel
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    (Original post by RedRosesBloom)
    Oh **** it's ammonium sulfide!!!! not sulphate.
    That was a b***chy question haha managed to suss it out tho
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    (Original post by Bosssman)
    That was a b***chy question haha managed to suss it out tho
    I was so tired! Didn't have enough sleep that's why
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    I marked my paper. Got 57/70. So many idiotic mistakes
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    which ones in that are wrong?
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    I've updated the mark scheme with all the questions, answers and marks
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    (Original post by ronnydandam)
    which ones in that are wrong?
    I've updated this one with all the correct answers
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    If on the last question i put X2 instead of giving a specific halogen will i get the mark? and i know it's a long shot but would i get a mark for saying for the water of crystallization question that they could get an anhydrous salt, hydrate it and see if the percentage change is the same as the percentage change when he removed the water
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    (Original post by therealbatman365)
    *No of atoms in 5.00g coin: 3.98 x 10^22 (3sf) *

    For this one, I got 3.97 x 10^22 for using the RAM calculated in the part before?? Did you have to use the periodic table one or the calculated one?
    I used both as a check and both gave me 3.98×10^22
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    (Original post by Bosssman)
    Here's my attempt at an unofficial mark scheme, it is for the OCR Chemistry A, new spec, breadth in chemistry paper, really can only put the maths questions down, but if there are written ones I can remember I will put them down. This is only really for comparison of numbers, and general ideas

    Multiple choice:
    BCDACCBDCBCBBCBDDBBD [20] (if anyone happened to store their multiple choice answers on their calculator, please post them below to compare)

    Similarities and differences of isotopes: Same number of protons and electrons, different number of neutrons [2]
    Relative atomic mass: 63.62 [2]
    No of atoms in 5.00g coin: 3.98 x 10^22 (3sf) [2]
    Equation with nickel (II) oxide and nitric acid: NiO + 2HNO3 --> Ni(NO3)2 + H2O [1]
    Dot and cross: [2]
    Empirical formula with water of crystallisation: CrCl3 • 6H2O [3]
    Percentage error of water removed mass: 1.72% [2]
    Ways to reduce percentage uncertainty: use a larger mass of crystals to get larger mass of water removed, reducing % error [1]
    To make sure mass of water removed is correct: reweigh and reheat, repeat until constant mass is achieved [1]
    Volume of H2SO4 required to neutralise NaOH: 24.8cm^3 [3]
    Oxidation: Al oxidised from 0 to +3 and H reduced from +1 to 0 [2]
    Electron configuration of bromide ion: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 [1]
    Displacement question: Cl2(g) + 2Br-(aq) = 2Cl- (aq) + Br2 (aq) [1] chlorine is more reactive than bromine [1]
    Adding chlorine to water: benefit, kills bacteria, risk, chlorine is toxic [1]
    Reagent for halide precipitate: AgNO3 (aq) [1]
    Halogen precipitate colours: chloride, white; bromide, cream; iodide, yellow [1]
    Enthalpy change of reaction: -58.5 kJmol^-1 [4]
    Ionic equation: Pb2+(aq) + 2I-(aq) = PbI2 (s) [1]
    Concentration of KI required: 3.3 moldm^-3 [2]
    Equilibrium question: The equilibrium position will shift to the right, as the forward reaction is exothermic, in an attempt to reduce the effect of the temperature decrease. The equilibrium position will also shift to the right as there are fewer gas molecules in the products of the forward reaction, in an attempt to reduce the effect of the pressure increase. This may vary to the actual conditions as low temperature reduces rate of reaction, and it's expensive to have a high pressure. [5]
    Concentration in equilibrium question: 0.876 moldm^-3 [4]
    Homologous series: alkenes, general formula: CnH2n [1]
    Alkene to alkane: H2, nickel catalyst, 150 degrees C [1]
    Alcohol --> H2SO4 + heat --> alkene (this question was to draw the alcohol I think) [1]
    Empirical formula: C2H5O [1]
    Last question: step 1 reagent, Cl2/Br2/I2, step 2 reagent, NaOH [3]

    Any incorrect (although I don't think there are) please tell and I'll correct

    Also, post about how you found the exam, as this will give a good indication of grade boundaries
    Last step 2 reagent would probably allow KOH and probably LiOH as well
    Potentially water but not sure on that
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    Looking at all the stupid mistakes I did from not reading the questions properly
 
 
 
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