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

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Does anyone know if anybody has done an unofficial mark scheme? Would be much appreciated!
I thought exam was great. I've seen different answers for it but I got 1062 for CO bond enthalpy question

Yeh I got 1062 as well

Reply 181

Bethaaaaany

Think I got quite a few calculation errors in that exam, totally kicking myself...I got 2. something litres for the petrol question :s-smilie:

Reply 182

#iamthewalrus

I went through all my numerical answers and stored them in my calculator. They are as follows:

14.1
-347
0.38
-281
1482
259
715

This is in the order of the actual paper.

Reply 183

yusraa_96

Original post by jirapat121

No we're definitely correct because the question stated that they want to make 5g that's mean 5g is the theoretical mole.

i think 5g was the actual moles, because you actually wanted to make 5g, so you work out the theoretical moles then calculate the mass of it.

so, mols actal (was 0.07..something)/theoretical moles=0.45, then work out theoretical moles and calculate mass by doing theoretical moles x Mr=mass

Reply 184

yusraa_96

Original post by #iamthewalrus

I went through all my numerical answers and stored them in my calculator. They are as follows:

14.1
-347
0.38
-281
1482
259
715

This is in the order of the actual paper.

How did you get 715 for the number of monomers in the polymer question?

I worked out the Mr go the monomer which was C6H12 =84 mol-1
then 50000/84=595.2 therefore 595 monomer units.

Reply 185

nadrxj

Original post by yusraa_96

How did you get 715 for the number of monomers in the polymer question?

I worked out the Mr go the monomer which was C6H12 =84 mol-1
then 50000/84=595.2 therefore 595 monomer units.

The monomer had an Mr of 70

Reply 186

GetOverHere

Original post by yusraa_96

How did you get 715 for the number of monomers in the polymer question?

I worked out the Mr go the monomer which was C6H12 =84 mol-1
then 50000/84=595.2 therefore 595 monomer units.

The Mr was 70. You may have drawn the wrong repeat unit. You'll probably get ECF though. 50000/70= 714.28..., then round up to 715. I rounded down personally but I think it's still fine, even though it doesn't give an Mr of exactly 50000.

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Reply 187

yusraa_96

Original post by nadrxj

The monomer had an Mr of 70

Oh I must have miscounted that!

Reply 188

#iamthewalrus

Original post by yusraa_96

How did you get 715 for the number of monomers in the polymer question?

I worked out the Mr go the monomer which was C6H12 =84 mol-1
then 50000/84=595.2 therefore 595 monomer units.

I got the repeat unit as C5H10, which has an Mr of 70. 50,000 / 70 = 714.2... which rounds up to 715

My monomer was CH3CHCHCH2CH3
Screen Shot 2016-06-10 at 10.17.06 PM.png

Screen Shot 2016-06-10 at 10.17.06 PM.png

Reply 189

yusraa_96

Original post by #iamthewalrus

I got the repeat unit as C5H10, which has an Mr of 70. 50,000 / 70 = 714.2... which rounds up to 715

My monomer was CH3CHCHCH2CH3
Screen Shot 2016-06-10 at 10.17.06 PM.png

I don't know why but i thought the polymer looked like this:
Screen Shot 2016-06-10 at 22.30.44.png

Reply 190

#iamthewalrus

Original post by yusraa_96

I don't know why but i thought the polymer looked like this:
Screen Shot 2016-06-10 at 22.30.44.png

That looks like the chain of the polymer they give you?

Reply 191

yusraa_96

Original post by #iamthewalrus

That looks like the chain of the polymer they give you?

exactly, so wouldn't the monomer look like this:
Screen Shot 2016-06-10 at 22.37.38.png

Reply 192

#iamthewalrus

Original post by yusraa_96

exactly, so wouldn't the monomer look like this:
Screen Shot 2016-06-10 at 22.37.38.png

I can't exactly remember it tbh, but I think you have one carbon too many on the right branch.

Reply 193

yusraa_96

Original post by #iamthewalrus

I can't exactly remember it tbh, but I think you have one carbon too many on the right branch.

Yeah thats what I thought, anyway hopefully I drew it correctly in the exam question, but I do remember the mr adding up to 84 :s-smilie:

Reply 194

tomlam

Original post by yusraa_96

exactly, so wouldn't the monomer look like this:
Screen Shot 2016-06-10 at 22.37.38.png

Wasn't it one less CH2 though? (on the bottom part of the chain)

It would be H3C-CH=CH-CH2-CH3

I might have forgotten myself tbh :P

Reply 195

yusraa_96

Original post by tomlam

Wasn't it one less CH2 though? (on the bottom part of the chain)

It would be H3C-CH=CH-CH2-CH3

I might have forgotten myself tbh :P

You might be right, it seems like most people it remember it that way, such a silly mistake on my part though

Reply 196

#iamthewalrus

Original post by yusraa_96

Yeah thats what I thought, anyway hopefully I drew it correctly in the exam question, but I do remember the mr adding up to 84 :s-smilie:

Don't worry about it, you've probably lost max 1 mark

Reply 197

yusraa_96

Original post by #iamthewalrus

Don't worry about it, you've probably lost max 1 mark

Yeah its not such a big deal i guess. I need 130 Ums for an A, and i think I've dropped about 5 marks so it might be close

Reply 198

ShannonD_1697

I think it was around 37/60 for a C on f321 last year could be wrong not sure..

Reply 199

NervousBoy

Enthalphy of CO was +1602 just saying, and they accept 714 NOT 715 according to my paper from last year where is its not a whole number you always round down assuming there is a lack of 'materials' to produce that extra repeat unit.