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# OCR Chemistry B (Salters) F334/F335 Exam Thread 2016 (14th/22nd June) watch

1. (Original post by Bruhh)
I got 390 for that,

Anyone else really dislike this paper? Where were the transition metals/complexes at?!
#390club
2. For the 5 marker of bromine this is the method I used:

After working out the moles of BrO3- in the previous question (= 0.005 moles and so was in excess) and looking at the reaction equation given, you know that the ratio of BrO3- was 1:3 for Br2, so the moles of Br2 is 3x0.005 = 0.015

We also know that it was 0.015 moles of br2 in 200cm3, but the hexadiene molecule only reacts with 83, so 0.015/200x83? I think

So that's the moles of br2 reacted is worked out, so you multiply that by mass of bromine and then x2 because two bromine molecules.

Lastly you times that by 10 because for bromine number it is of 100g of hexadiene whereas the question said 10g.

I don't know if this is right, this is just what I did. Anyone do the same?
3. (Original post by ParcelFace)
#390club
I got 390 too!
4. a few questions:
what was the electrode potential of V3+?
what was put over steel to protect it?
Which electrode was the tank 1 on which was tank 2?
What was the need of the thing in the middle of the 2 tanks?
5. (Original post by ParcelFace)
#390club
#390club IT was a 1:2 ratio in the first question so it wasn't 195
6. (Original post by IBerrr)
For the 5 marker of bromine this is the method I used:

After working out the moles of BrO3- in the previous question (= 0.005 moles and so was in excess) and looking at the reaction equation given, you know that the ratio of BrO3- was 1:3 for Br2, so the moles of Br2 is 3x0.005 = 0.015

We also know that it was 0.015 moles of br2 in 200cm3, but the hexadiene molecule only reacts with 83, so 0.015/200x83? I think

So that's the moles of br2 reacted is worked out, so you multiply that by mass of bromine and then x2 because two bromine molecules.

Lastly you times that by 10 because for bromine number it is of 100g of hexadiene whereas the question said 10g.

I don't know if this is right, this is just what I did. Anyone do the same?
Yes i did the exact same, I got 59 I think as the answer. Anyone else get the same?
7. (Original post by Aspire7736)
It never quadrupled because the two of them halved and the third doubled with the rate staying the same so it was second order
That is correct as far as i know.
8. I got that too!
9. did everyone else draw 4 different molecules for the E/Z isomers?
10. #390club what did people get for the other bromine number one?
I got 7?

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11. (Original post by GetMeToUni99)
a few questions:
what was the electrode potential of V3+?
what was put over steel to protect it?
Which electrode was the tank 1 on which was tank 2?
What was the need of the thing in the middle of the 2 tanks?
I put zinc

Acts as a salt bridge
12. (Original post by ParcelFace)
#390club
How can it be 390 g of bromine in 100 g of the sample? I got 70
13. Bye bye Cambridge offer
14. (Original post by ParcelFace)
#390club
I got 390 🙌
15. (Original post by jack.lp.thompson)
Fe2+ is oxidised to Fe3+ by the airFe2+ => Fe3+ + e-This makes all the iron become Fe3+They all react with the -OH ion like so:Fe3+ + 3OH- => Fe(OH)3 (s)Iron(iii) hydroxide is a red brown precipitate.Something like that but with better English 😊
Wouldn't the transition metal ion be surrounded by Aqua Ligands forming a complex ion which then undergoes ligand substitution to form the precipitate?
16. (Original post by ben_tyler28)
Hi, did anyone also get 7 for bromine number, worth 5 marks, in the f334 exam?
Yeh boii

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17. (Original post by dickbutt)
Yes i did the exact same, I got 59 I think as the answer. Anyone else get the same?
I got 10g as my final answer btw
18. Grade boundaries should be around 56 for an A. That's not unreasonable considering the paper Look at how many of the questions had not come up before in any way shape or form. First time I've seen cold drawing, First time I've seen 10marks worth of maths in one question (bromine number). First time recrystallisation has ever been 3 marks. First time heterogeneous catalysis has been asked. First time that we have been asked to show something is in excess.First time that I've seen a 5 mark question on rusting iron and been given 3 lines to put it on. It's an absolute disgrace of a paper and some action will have to be taken if the grade boundaries do not reflect it's difficulty. OCR if you are reading this then its not to say go and make F335 easy to make up for your questions. Make it like you do every year, so that those who work hard get what they deserve.

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19. (Original post by Amyfrancis97)
Is it just me that found this paper ridiculously hard? So frustrating. Anyone else not answer the calculation either?
it was so so hard compared to other past papers
20. I drew 3 isomers because the isomer with one E and one Z double bond could just be reflected to get the isomers which has the E and Z's the other way round. Did anyone else put three because one of them could just be reflected in a mirror to get the other one?

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