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OCR GCSE Chemistry C4,5,6 UNOFFICIAL MARKSCHEME Watch

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    (Original post by JackTinker)
    For the last 6 markers, I said that B was the best choice as it was 61p cheaper than C, had the best cost per wash, and was almost identical to C apart from 1 point of in terms of whiteness.
    I said B as well!
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    How do you think the grade boundaries are gonna be this year? High? Low? I can't tell as I've seen a mixed review on how people found the paper
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    (Original post by XxxVxxX)
    How do you think the grade boundaries are gonna be this year? High? Low? I can't tell as I've seen a mixed review on how people found the paper
    I think the grade boundaries will be high because the exam was easier than previous papers; but i dont think it will increase by a lot just marginally, like 1 or 2 marks.

    Hopefully i get an A*
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    (Original post by JackTinker)
    For the last 6 markers, I said that B was the best choice as it was 61p cheaper than C, had the best cost per wash, and was almost identical to C apart from 1 point of in terms of whiteness.
    the question specifically said what was the best detergent to wash with, our teachers have always drilled into our head that cost should never be a factor when choosing the better one as it's not an economic exam
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    (Original post by pratam)
    are more are added on the left it compensates and the equilibrium shifts to the right
    yeah look at this link and scroll down
    https://chem.libretexts.org/Core/Phy...39;s_Principle
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    (Original post by JackTinker)
    For the last 6 markers, I said that B was the best choice as it was 61p cheaper than C, had the best cost per wash, and was almost identical to C apart from 1 point of in terms of whiteness.
    That is what i said too so hopefully someone sees our way of thinking
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    (Original post by Livi_efc)
    That is what i said too so hopefully someone sees our way of thinking
    as long as you explained it well then you would get some marks
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    i think it was astatine rather than iodine for the 6 marker but if you didnt have to name them it doesnt matter
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    Also with the concentration question i was so confused because despite the concentration changing, they used the same volume of acid so shouldnt the amount of gas produced still be the same, just have a faster rate of reaction. that is what we were taught for c3 anyways
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    is this the chemistry 2016 as depth paper ?
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    (Original post by rishigubala)
    is this the chemistry 2016 as depth paper ?
    no it literally says in the title GCSE OCR Gateway
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    (Original post by TheNlee)
    If I forget anything, write in the comments

    C4
    Question about ions and atoms
    - Mg+ (1)
    - MgFl2 (1)

    Why and how do Lithium atoms form ions
    -It loses electrons to become stable (1)
    -It loses one electron: Li- -> Li + e- (1)

    Draw Na20
    -dot and cross diagram with 2- charge on Oxygen atom and +1 charge on both sodium atoms

    Table to fill in with Protons, Neutrons (2)
    Protons: 1, +1 (1)
    Neutrons: 1, 0

    Why is the atom neutral?
    -It has the same number of protons as electrons (1)

    Size of Atom- C
    forgot the q after that

    What happened to Zinc Carbonate when heated (3)
    -Thermal Decomposition (2)
    -Zinc oxide and co2 emitted (1)

    Predict the properties of ammonia (4)
    -Gas at room temperature
    -Doesn't conduct electricity
    -Low melting and boiling point due to weak IM bonds

    Balancing:
    CaCO3 + 2HCl -> H20 + CaCl2 + CO2 (2)

    6 marker on Halogens and reactivity
    -Reaction Cl2 + 2NaBr -> 2NaCl + Br2
    -Order: Z (Fluorine) ,Cl,Y (Bromine),X (Iodine) (Dont have to name them)
    Explanation: Z displaced 3 solutions, Cl displaced 2, Y displaced 1 and X displaced 0

    C5
    Titration:
    22 (1)
    20(1)

    30cm3 = 0.03 dm3
    0.03*0.3= 0.009 mol (1)

    Concentration is 0.45moldm-3 (2)

    Percentage of Magnesium: 28.7% (not sure) (1)

    Explain what is relative atomic mass:
    -Number of protons and neutrons

    mass of hydrogen: 0.004g (2)
    -48cm3 = 0.048dm3
    0.048/24= 0.002mol
    0.002*2=0.004g

    Contact Process question (screwed this one up)

    Under what conditions and why the reaction is at equilibrium:
    -closed system (2)
    -forward reaction same as backward reaction (1)

    Position of equilibrium when Oxygen is added:
    -Shifts to the right (1)

    Conditions of Contact Process:
    -Vanadium Pentoxide (V2O5) Catalyst (1)
    -High temp: 450C (1)

    Conclusions about concentration of hydrogen:
    Both right i think (2)

    6 marker on preparing insoluble salts
    Equation: Pb2+ 2I- -> PbI2
    Method:
    Precipitate-add lead nitrate to distilled water and do the same with the other and tip both solutions to a small beaker
    Filter-put a piece of folded filter paper into funnel and stick funnel into conical flask and then swill out the beaker with more distilled water
    Dry- Rinse contents with distilled water to wash soluble salts away, leave it to dry
    C6
    Rusting of iron equation:
    -Water + Oxygen + Water -> Hydrated Iron (III) Oxide (1)

    Galvanising question:
    -Done with zinc and acts as sacrificial protection so it will lose electrons in preference to iron (1)
    -Acts as a barrier to water and air (1)

    Redox reaction: oilrig cheeky mention
    -Reduction happens to Iron as it gains electrons (1)
    -Magnesium is oxidised as it loses electrons (1)
    Redox since both happening at same time

    Alternative to ozone:
    -Alkane (1)

    In terms of electons, how is Chlorine and Carbon bonds split:
    -Covalent bond is broken evenly where both chlorine and carbon get one of the electrons (making them both highly reactive as radicals) (2)

    Why did attitudes to CFCs change (2)
    -They found out Chlorine from CFCs could destroy ozone
    -They found out that CFCs cause the depletion of Ozone Layer

    Energy Level Diagram
    -Exothermic as energy is released, there is less energy in the product (1)

    Fuel Cell Question:
    -O2 + 4H+ + 4e- -> 2H20 (2)

    Which solution is temporary:
    -A as it had hardness before boiling and none after (2)

    What causes permanent hardness in water
    -Calcium Sulfate (1)

    6 marker on Detergents:
    -Peter was right as it had excellent whiteness and something else and had very good prevention of colour fading

    -Detergents have a hydrophilic head and a hydrophobic tail.
    -Grease has weak IM bonds in between and so does the detergent
    -The detergent forms stron IM bonds with grease due to hydrophobic tail
    -Hence the detergent surrounds the grease and attaches to water
    -Lifting the grease off of the clothes

    Dry Cleaning:
    -Solvent used is not water (1)
    -Water can damage delicate linen (1)

    SECTION D
    idk
    Relative atomic mass is wrong - it is the average mass of an element compared to the mass of 1/12th of an atom of Carbon-12

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    (Original post by TheNlee)
    If I forget anything, write in the comments

    C4
    Question about ions and atoms
    - Mg+ (1)
    - MgFl2 (1)

    Why and how do Lithium atoms form ions
    -It loses electrons to become stable (1)
    -It loses one electron: Li- -> Li + e- (1)

    Draw Na20
    -dot and cross diagram with 2- charge on Oxygen atom and +1 charge on both sodium atoms

    Table to fill in with Protons, Neutrons (2)
    Protons: 1, +1 (1)
    Neutrons: 1, 0

    Why is the atom neutral?
    -It has the same number of protons as electrons (1)

    Size of Atom- C
    forgot the q after that

    What happened to Zinc Carbonate when heated (3)
    -Thermal Decomposition (2)
    -Zinc oxide and co2 emitted (1)

    Predict the properties of ammonia (4)
    -Gas at room temperature
    -Doesn't conduct electricity
    -Low melting and boiling point due to weak IM bonds

    Balancing:
    CaCO3 + 2HCl -> H20 + CaCl2 + CO2 (2)

    6 marker on Halogens and reactivity
    -Reaction Cl2 + 2NaBr -> 2NaCl + Br2
    -Order: Z (Fluorine) ,Cl,Y (Bromine),X (Iodine) (Dont have to name them)
    Explanation: Z displaced 3 solutions, Cl displaced 2, Y displaced 1 and X displaced 0

    C5
    Titration:
    22 (1)
    20(1)

    30cm3 = 0.03 dm3
    0.03*0.3= 0.009 mol (1)

    Concentration is 0.45moldm-3 (2)

    Percentage of Magnesium: 28.7% (not sure) (1)

    Explain what is relative atomic mass:
    -Number of protons and neutrons

    mass of hydrogen: 0.004g (2)
    -48cm3 = 0.048dm3
    0.048/24= 0.002mol
    0.002*2=0.004g

    Contact Process question (screwed this one up)

    Under what conditions and why the reaction is at equilibrium:
    -closed system (2)
    -forward reaction same as backward reaction (1)

    Position of equilibrium when Oxygen is added:
    -Shifts to the right (1)

    Conditions of Contact Process:
    -Vanadium Pentoxide (V2O5) Catalyst (1)
    -High temp: 450C (1)

    Conclusions about concentration of hydrogen:
    Both right i think (2)

    6 marker on preparing insoluble salts
    Equation: Pb2+ 2I- -> PbI2
    Method:
    Precipitate-add lead nitrate to distilled water and do the same with the other and tip both solutions to a small beaker
    Filter-put a piece of folded filter paper into funnel and stick funnel into conical flask and then swill out the beaker with more distilled water
    Dry- Rinse contents with distilled water to wash soluble salts away, leave it to dry
    C6
    Rusting of iron equation:
    -Water + Oxygen + Water -> Hydrated Iron (III) Oxide (1)

    Galvanising question:
    -Done with zinc and acts as sacrificial protection so it will lose electrons in preference to iron (1)
    -Acts as a barrier to water and air (1)

    Redox reaction: oilrig cheeky mention
    -Reduction happens to Iron as it gains electrons (1)
    -Magnesium is oxidised as it loses electrons (1)
    Redox since both happening at same time

    Alternative to ozone:
    -Alkane (1)

    In terms of electons, how is Chlorine and Carbon bonds split:
    -Covalent bond is broken evenly where both chlorine and carbon get one of the electrons (making them both highly reactive as radicals) (2)

    Why did attitudes to CFCs change (2)
    -They found out Chlorine from CFCs could destroy ozone
    -They found out that CFCs cause the depletion of Ozone Layer

    Energy Level Diagram
    -Exothermic as energy is released, there is less energy in the product (1)

    Fuel Cell Question:
    -O2 + 4H+ + 4e- -> 2H20 (2)

    Which solution is temporary:
    -A as it had hardness before boiling and none after (2)

    What causes permanent hardness in water
    -Calcium Sulfate (1)

    6 marker on Detergents:
    -Peter was right as it had excellent whiteness and something else and had very good prevention of colour fading

    -Detergents have a hydrophilic head and a hydrophobic tail.
    -Grease has weak IM bonds in between and so does the detergent
    -The detergent forms stron IM bonds with grease due to hydrophobic tail
    -Hence the detergent surrounds the grease and attaches to water
    -Lifting the grease off of the clothes

    Dry Cleaning:
    -Solvent used is not water (1)
    -Water can damage delicate linen (1)

    SECTION D
    idk
    Fuel Cell Question:
    -O2 + 4H+ + 4e- -> 2H20 (2)

    wouldn't it be O2 + 4H+ + 4e- -> 2H20 cause if there was an -O2 then the water will be a negative ion cause the electron balances the hydrogen ion.
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    (Original post by KingdomGudManga)
    Fuel Cell Question:
    -O2 + 4H+ + 4e- -> 2H20 (2)

    wouldn't it be O2 + 4H+ + 4e- -> 2H20 cause if there was an -O2 then the water will be a negative ion cause the electron balances the hydrogen ion.
    lol the O2 isn't meant to have a charge, the - was because of formatting for a list dw

    -Like this
    -Do you understand
    -O2
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    (Original post by Karim.H17)
    Relative atomic mass is wrong - it is the average mass of an element compared to the mass of 1/12th of an atom of Carbon-12

    Posted from TSR Mobile
    didn't see the relative part oops my mistake
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    (Original post by Anon4012)
    Hi there, I have a query about the first 6 marker. I got the opposite way round from your answers, my idea being:

    If X has no reaction with none of the three it must therefore be more reactive as the other solutions don't displace it?

    I see your way of thinking, just hoping somebody can floor my thinking????

    sorry no...if it doesnt react with anything..then its least reactive
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    (Original post by anonna)
    sorry no...if it doesnt react with anything..then its least reactive
    If it can't replace another ion it is less reactive
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    if u dont get the balanced equation bit right in the 6 marker do u lose like a max 3 marks??
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    (Original post by azizkahdijaaaa)
    if u dont get the balanced equation bit right in the 6 marker do u lose like a max 3 marks??
    ur capped at a certain level which is either max 4 marks or 2 marks but dw about it you'll do great
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    There was one question on zinc carbonate and what happens when it is heated
 
 
 
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