OCR Chemistry A C1,2,3 GCSE Unofficial markcheme help!!!!

This exam was so much harder than B1 B2 B3 Biology. What are your thoughts on Physics tomorrow?

This is brill! How did you manage to get a copy of the paper?
Oh and for 4(b)(iv) I put: yes because the two sets of data show a real difference as the ranges don't overlap, and also the mean for ruler A doesn't fall within the range for ruler B and vice versa. (Not 100% sure though but I was proud)

I'm hoping that it follows the trend of the biology and chem exams and its not too bad... i have a feeling maybe the carbon cycle might make an appearance as it wasnt in the bio exam??? not sure... thats my opinion!!

I managed to get hold of a spare exam booklet of the OCR Chemistry A c1,2,3 exam and was wondering if we could all work together and make an unofficial markscheme?
I have numbered all the questions and what they were below and have answered some of the smaller questions that I know as 6 markers are harder to write about!! BOLD= need an answer or more points needed feel free to add any more knowledge this is what i have done so far


1a) Q: Suggest why ethyne is burned in oxygen rather than air
A: Pure oxygen means the reaction happens faster OR unpure air contains other elements which could react with the ethyne
b) Q: What type of compound is ethyne? A: Hydrocarbon
c) Q: Complete the molecule diagram A: should be 4 CO2 molecules and 2 molecules of water including the ones already done for you
2a) Q:Which 2 sentences explain why carbon monoxide and particulate carbon form??
A: some carbon atoms in the fuel react with oxygen in the air AND there is not enough oxygen for complete combustion
b) Q: Complete the sentences about the chemical reaction in a catalytic converter
A: In a catalytic converter CARBON MONOXIDE is oxidised to CARBON DIOXIDE. At the same time NITROGEN MONOXIDE is reduced to NITROGEN
c)Q: Advantages and disadvantages of diesel cars over petrol cars (6 marker) ANSWER NEEDED
3ai) Q: Estimate amount of fossil fuels that will be burned in 2020 ANSWER NEEDED - i got 11000 but not sure?? I got 10200 - there'll be a big range for this one
ii) Q: John says that it is very difficult to estimate the amount of fossil fuel we will use in 100 years' time
A: Fossil fuels could have run out as they are non renewable
Alternative methods may be used instead of fossil fuels
b) Q: Describe link between the trends of the two graphs
A: Positive correlation, as one increases so does the other MORE POINTS NEEDED
4a) Q: Which plan is best, why is it better than the other two?
A: Obviously Matt - tests 4 times whereas others dont, calculates mean, fair test etc.
bi) Q: Which measurement is the outlier?
A: 13
ii) Q:What could the students do to decide whether to include the outlier when calculating the best estimate of the true value from their measurements
iii)Q: Include outlier and work out best estimate of the true value
A: 23+26+13+19+24= 105 105/5 = 21
iv) Does the data support whether ruler A and B are made from different plastics? Answer I gave
5) Q: Crude oil 6 marker
6a) Q: Name missing element in PVC molecule A: Chlorine
ii) Q: Draw diagram to show one monomer of PVC A:carbon attached to 2 hydrogen and carbon attached to 1 hydrogen and 1 chlorine atom
bi) Explain how adding plasticisers makes PVC more flexible
A: Increases space between polymer chains, easier for chains to slide past eachother
ii) Q: Explain why some scientists think that plasticised PVC is not safe when in contact with food
A : Plasticiser can leach out of the PVC and the food can absorb it and could have serious health problems for consumer bioaccumulation
7) LCA assessment 6 marker
8a) Solution mining correct steps in correct order
A: BAGCD
7aii) Salt improves taste of food. What else?
A: Preservation
bi) Products of electrolysis
A: Hydrogen and sodium hydroxide
ii) Fill in table
A: top row = 1600000 i think.. and not sure for middle value HELP PLEASE!! 1.6x10⁶ and 10000
iii) Use data to discuss how production of chlorine has changed over the past 50 years

My alterations are in red

Thank you !! Yeah wasn't sure about everything

Chemistry and biology have been too good to be true, really hope physics is not similar to last years one, the calculations were long and under pressure it is easy to make mistakes

IS this for 21st century science ??