OCR Chemistry F322 June 2016

Scroll to see replies

Reply 240

lndonmania22

Can you guys tell me answers you got for the percentage yield question?

Reply 241

GawdHeresEmmie

Original post by mercuryman

Nah trust me it is 14 we both made a mistake dw

Original post by Lion2121

how though?

I got 11.1g xxx

Reply 242

GawdHeresEmmie

Original post by Apple Core

Did anyone of u get CH3CH2CH2CH2Br as the the isomer. Because I calculated the empirical formula which gave me C3H7Br. Then to find the molecular formula I did Mr which was 150 divided by the Mr of empirical formula which gave me like 1.22... multiplied this with the empirical formula. Which gave me C3H9BR. Is this wrong?

It said that the max Mr was 150, Mr or C3H7Br is like 122.9 which cannot be multiplied by any whole number ratio and be under 150 therefore empirical = molecular.

Original post by Apple Core

Original post by Randall13

How did you get C5H10 in my last post the repeating unit is C6H12 so the Mr would be 84.

I got C5H10 as well, Mr of 70 per monomer

Reply 243

GawdHeresEmmie

Original post by ali_t9001

Don't suppose you can remember how many marks that question was worth?

3; I'm assuming one mark for each structure and one mark for having a positive charge on both xx

Reply 244

Randall13

Original post by Manliker

It was not only a2 people lol, some schools are still doing last years course so there was some AS students. Also it wouldn't matter if it was just A2, the grade boundaries wouldn't change

What do you think for grade boundaries? It's subjective but just a guess tbh.

Reply 245

milutin767

Original post by Randall13

What do you think for grade boundaries? It's subjective but just a guess tbh.

It could never go above 85 but I guess around 82-83 because of difficult stoichiometry questions

Reply 246

Rhy

Original post by ali_t9001

Of the polymer? 50 000 / 70 I think. Can't remember very clearly. But, if I remember correctly, the individual monomers were C5H10 -- meaning the number of monomers in mr= 50 000 would be 714.285. I rounded that down to 714 as the actual number of monomers would be a whole number

You would have to round up if you think about it logically, 714 monomers would have a total mr of less that 50000

Reply 247

HediIsLord

Original post by Rhy

You would have to round up if you think about it logically, 714 monomers would have a total mr of less that 50000

same principle. 715 x 70 is further from 50000 than 714 x 70 regardless

Reply 248

hannahbriddon

I think i completely mucked up this paper, so do you guys know if they'll do another resit next year. I've looked on the ocr website and there is a provisional date for it but i was told they wouldn't be doing another resit by my teacher ?

Reply 249

lukemurp890

The grade boundary predictions from the guy running the 'A-Level Chemistry' Twitter page:

A- 84
B- 75
C- 66
D- 57
E- 48

He's a Chemistry teacher, so his predictions are probably more informed than ours.

Posted from TSR Mobile

Reply 250

Manliker

Original post by Randall13

What do you think for grade boundaries? It's subjective but just a guess tbh.

I would say 84 for an A, 76 for a B and 66 for a C

Reply 251

Bgxx

Does anyone have access to the paper?

Reply 252

jadder1224

any of you guys get this?

Reply 253

FluffyCommie

Original post by jadder1224

any of you guys get this?

From a quick read of it that generally seems like the correct answer, but just because i've seen it in a mark scheme, for what happens in a catalytic converter, i recommend saying that the bonds are weakened AND the products are allowed to chemically react. (then the products desorb, of course)

Reply 254

Rxhiem

Original post by jadder1224

any of you guys get this?

I think you also have to mention that the activation energy is lowered as well as the bonds weakening

Reply 255

Rxhiem

Does anyone have an unofficial mark scheme yet?

Reply 256

lolpool

Original post by milutin767

It could never go above 85 but I guess around 82-83 because of difficult stoichiometry questions

Am i wrong in thinking that this is still really high?
i though average was 75 :frown:

Reply 257

mercuryman

Original post by GawdHeresEmmie

No2 itself is an nitrogen oxide

I just remembered I put down burning nitrated fuels ie nitroethane as well and thunderstorms

Surely that would count? Lolololol

Reply 258

loren.o

Original post by Saywhatyoumean

Also I got -281 for the enthalpy question I think I did something wrong :/

Posted from TSR Mobile

I got +281 ..

Reply 259

loren.o

okay so im really bad at maths so i wanna see what everyone else got for some of these calculations..
enthalpy of reaction i got -0.145
+ 25% mass of Mg 119.7g
enthalpy of formation +281
bond enthalpy of C double O +1062
weird petrol one i got upto that 1l fuel gave 3l CO2..
and number of monomers 596
???? am i way off or..