OCR Chemistry A Exam Thread (Breadth - May 27 2016 and Depth - June 10 2016)

are you allowed to write in bullet points for the 6 marker ?

Reply 744

Firenze26

Original post by money-for-all

are you allowed to write in bullet points for the 6 marker ?

Pretty sure it's no. I believe they're being pretty strict on the QWC in this new spec.

Reply 745

Original post by Bahcaci

Chances are you will be asked to write the mechanism (free radical) of ozone depletion & also the name of the steps. And here it is:

Initiation:
Cl2 --> 2Cl•

Propagation:
Cl• + O3 --> ClO• + O2
ClO• + O --> Cl• + O2
(*Small note, notice the Cl• is reformed, so this reaction can go on for a long time, even after we stop use of CFCs)

Termination:
Cl• + Cl• --> Cl2 (main one!)
Cl• + ClO• --> Cl2O
ClO• + ClO• --> Cl2O2

Do you mind explaining where the O in propagation 2 comes from?

Reply 746

4nonymous

Original post by asinghj

Do you mind explaining where the O in propagation 2 comes from?

He did it wrong. It should be:
ClO• + O3 --> Cl• + 2O2

Reply 747

PLEASE HELP ME WITH THIS

"1.40 g of calcium oxide was reacted with 50.0 cm³ of HCl in a polystyrene cup to produce a temperature rise of 10.0 degrees"

Why is the total mass in q = mc (delta)t actually 51.4g not 50g [if density = 1.00 cm³]

Reply 748

Sajjjid

Original post by 11...

using the cgp revision guide would be really useful at this point to refresh yourself with all the content cos doing past papers can get a little boring after a while and of course they do not have questions on everything. something that was never asked before may turn up tomorrow who knows, so cgp guides are best for last minute prep

LOL I made the mistake of using only a CGP guide for paper 1. I know, V stupid.

Reply 749

Original post by nwmyname

for mass , you use the contents of everything you are heating,
so you put 1.4g of CaO in a cup and then add 50cm³ (50cm³ = 50g)
hence total mass of what you are heating = 50 + 1.4 = 51.4 grams

let me know if that was a good enough explaintion^^
if not, ill try to explain it better

Reply 750

Original post by money-for-all

OH ok.
So you are looking at the enthalpy change of the ENTIRE mass of the solution including the CaO?

I would be grateful if you explained it better.

Reply 751

Original post by nwmyname

OH ok.
So you are looking at the enthalpy change of the ENTIRE mass of the solution including the CaO?

I would be grateful if you explained it better.

b**ch dont diss my answer, i will get me mandem on ya

cos' you were rude to me , now imma gonna go full ape on you bruv!!!

.you dumb head, how can you not know what the anwer is

Spoiler

Reply 752

Original post by money-for-all

b**ch dont diss my answer, i will get me mandem on ya

cos' you were rude to me , now imma gonna go full ape on you bruv!!!

.you dumb head, how can you not know what the anwer is

Spoiler

haha that made me laugh!
Thanks very much!

Reply 753

Original post by money-for-all

b**ch dont diss my answer, i will get me mandem on ya

cos' you were rude to me , now imma gonna go full ape on you bruv!!!

.you dumb head, how can you not know what the anwer is

Spoiler

I thought m was the mass of surrounding and not the whole thing

Reply 754

Original post by 4nonymous

He did it wrong. It should be:
ClO• + O3 --> Cl• + 2O2

Ok thx that explains it

Reply 755

Original post by asinghj

I thought m was the mass of surrounding and not the whole thing

oh my dayzzz fam,
are you dizzy fam?

you clown, i just said it is mass of what is being heated and then sidemen like you gotta go and confuse the whole mandem

Spoiler

Reply 756

Original post by money-for-all

oh my dayzzz fam,
are you dizzy fam?

you clown, i just said it is mass of what is being heated and then sidemen like you gotta go and confuse the whole mandem

Spoiler

Ok, I am ill the day before exam so won't even bother

Reply 757