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Ocr f321 , f322 retakes on 27/05/16 and 10/06/16

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Reply 140
Avatar for nae_xo
nae_xo
1
Original post by GetOverHere
It was something like the EU wants to reduce CO2 emissions by 2020 by 5.4 X 10^5 g(not sure on the exact figure). They gave the equation for complete combustion of octane, and said that how many liters of petrol less would a car have to burn in 2020 (then told us that a litre=700g).


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it was 5.6x10^5 not 5.4 :smile:


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Original post by nadrxj
Anyone else get something like 14g for the percentage yield question?


Yeah I got that like 14.08g
Original post by NervousBoy
Yeah I got that like 14.08g


Got 14.05, did you round on your workings at all?


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Original post by drandy76
Got 14.05, did you round on your workings at all?


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i got 14.05 as well but i put my final answer as 14, did it ask for specific d.p?
what did everyone get for the question where you had to work out the number of monomers in the polymer? was it 50000/70 or 50000/71?
Reply 145
Avatar for nadrxj
nadrxj
4
Original post by AJtheconfusedcat
what did everyone get for the question where you had to work out the number of monomers in the polymer? was it 50000/70 or 50000/71?


I got 50000/70 which came to like 715 or something, but I'm guessing you get ECF marks if your monomer was different
Original post by nadrxj
I got 50000/70 which came to like 715 or something, but I'm guessing you get ECF marks if your monomer was different


i did 50000/70 as well but it was 714? and i left it with some decimals, did it have to be a whole number?
Anyone else scared about the crazy high grade boundaries?

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Original post by GetOverHere
It was something like the EU wants to reduce CO2 emissions by 2020 by 5.4 X 10^5 g(not sure on the exact figure). They gave the equation for complete combustion of octane, and said that how many liters of petrol less would a car have to burn in 2020 (then told us that a litre=700g).


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Thanks! I agree with the others then, assuming that figure is right, should be 249 litres of petrol required.
I don't think it went that well, it was ok but not amazing like most people found it! What grade do you guys think 60marks will be roughly?


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Reply 150
Avatar for nadrxj
nadrxj
4
Original post by AJtheconfusedcat
i did 50000/70 as well but it was 714? and i left it with some decimals, did it have to be a whole number?


I rounded my answer up to 715 because of the wording of the question, I guess if you left it unrounded that would also work but if you rounded it down then they wouldn't be able to make at least 50,000 they would end up making less. I'm probably wrong though.
Original post by NervousBoy
This is what I remember from my calculations.

Magnesium Mass : 0.38 g or something along that

CO +1602
Volume: 259.09 Litres
Enthalphy of Nonane: -230 something
Enthalphy of Reaction using Temp change: -34.7 or similar
Repeat Units: 50000/70

Let me know what you guys got


Wasnt it 50,000/68 because it was an Mr of 70 for the hydrocarbon but only 68 for the monomers?
Ignore me, i ****ed that bit up. I forgot that only the dounle bond breaks the hydrogens stay put. My bad.
(edited 7 years ago)
Original post by NervousBoy
This is what I remember from my calculations.

Magnesium Mass : 0.38 g or something along that

CO +1602
Volume: 259.09 Litres
Enthalphy of Nonane: -230 something
Enthalphy of Reaction using Temp change: -34.7 or similar
Repeat Units: 50000/70

Let me know what you guys got


yeah that's all correct i got that too
i think you have to leave it as 715 despite that 50000/70 =714.285 because 714 monomers will not make Mr=50000 they will only make polymers with Mr=49980 but I think they will still allow 714 : )
Original post by jirapat121
i think you have to leave it as 715 despite that 50000/70 =714.285 because 714 monomers will not make Mr=50000 they will only make polymers with Mr=49980 but I think they will still allow 714 : )


Crap I wrote 714 because I left it in 3.s.f :|
Really hope they accept it :|
Original post by fastandfurious
Crap I wrote 714 because I left it in 3.s.f :|
Really hope they accept it :|

Yeah I think they will accept it because last year there was literally the same question asking to do the same calculations and I looked at the mark scheme of the last year paper and it said allow 1 lower than the answer
Original post by nadrxj
Anyone else get something like 14g for the percentage yield question?


I got 11.1 g by doing mass of product/0.45
What did you do?
Wait dw i see where i went wrong. I should have done 11.1/mr of product then * that by Mr of reactant
(edited 7 years ago)
Original post by NervousBoy
This is what I remember from my calculations.

Magnesium Mass : 0.38 g or something along that

CO +1602
Volume: 259.09 Litres
Enthalphy of Nonane: -230 something
Enthalphy of Reaction using Temp change: -34.7 or similar
Repeat Units: 50000/70

Let me know what you guys got


Exactly the same. Go us
The two Haloalkanes were CH3CH2CH2Br and CH3CHBrCH3

Then reacted with NaOH/reflux to form propan-1-ol and propan-2-ol

propan-2-ol reacted with the carboxylic acid to form an ester:

R-COOCH(CH3)2 (can't remember what the carboxylic acid was)
Part 1:
C3H7Br
Different isomers were just the Br being on a different carbon

Part 2:
C3H7OH
E is a primary alcohol
F is a secondary alcohol
G is a carboxylic acid

Part 3:
Ester is formed.
(edited 7 years ago)

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