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

Reply 220

ParcelFace

1

Original post by Bruhh

I got 390 for that,

Anyone else really dislike this paper? Where were the transition metals/complexes at?!

#390club

Reply 221

IBerrr

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?

Reply 222

Randomsher789

Original post by ParcelFace

#390club

I got 390 too!

Reply 223

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?

Reply 224

Toweringtin

Original post by ParcelFace

#390club

#390club IT was a 1:2 ratio in the first question so it wasn't 195

Reply 225

dickbutt

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?

Reply 226

scidak

4

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.

I got that too!

did everyone else draw 4 different molecules for the E/Z isomers?

Reply 229

Fozzy425

#390club what did people get for the other bromine number one?
I got 7?

Posted from TSR Mobile

Reply 230

Daniel9998

15

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

Reply 231

yoyo.sat

1

Original post by ParcelFace

#390club

How can it be 390 g of bromine in 100 g of the sample? I got 70

Reply 232

josephinemar25

2

Bye bye Cambridge offer :ciao:

Reply 233

dgreen311

Original post by ParcelFace

#390club

I got 390 🙌

Reply 234

lucyyyyy0

1

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?

Reply 235

Fozzy425

Original post by ben_tyler28

Hi, did anyone also get 7 for bromine number, worth 5 marks, in the f334 exam?

Yeh boii

Posted from TSR Mobile

Reply 236

IBerrr

2

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

Reply 237

Zuzuvela

2

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.

Posted from TSR Mobile

Reply 238

clo_ro

8

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 :frown:

Reply 239

Ligand

1

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?

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

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you