ocr a f325 revision thread

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does any one have pictures of the actual paper?

You can't show those publicly yet.

for the optical isomers will they allow ECF?

Cause I did Fe in the middle with 2 C2o4 2- and 2 h2o

cause I was thinking in order for optical to occur there either has to be 3 bidentate, or 2 mono or 2 bidentate,

cause it put in bracket (C2O4)2

There probably won't be ECF, it was only 2 or 3 marks.

Original post by NerdMeister

Can someone please explain how they got their answers for the rate of reaction after 40 seconds and the rate constant? Thanks :smile:

You draw a tangent to the graph at t=40, and the gradient is the rate. The rate constant is then found by doing rate/conc.

Reply 4101

alow

Original post by NerdMeister

Can someone please explain how they got their answers for the rate of reaction after 40 seconds and the rate constant? Thanks :smile:

Rate after 40s = dy/dx at 40.

k*half life=ln2 for rate constant

Reply 4102

username878045

Original post by needtosucceed=)

where you had to name the processes it was precipitation, redox, ligand substitution in that order right?

I don't think you had to name the precipitation reaction, but it was that order.

Reply 4103

otrivine

Original post by PythianLegume

You can't show those publicly yet.

There probably won't be ECF, it was only 2 or 3 marks.

You draw a tangent to the graph at t=40, and the gradient is the rate. The rate constant is then found by doing rate/conc.

But I am sure, I did it right it was (c2o4)2 which means two are present and u put 2 h2o

Reply 4104

NerdMeister

Original post by alow

Rate after 40s = dy/dx at 40.

k*half life=ln2 for rate constant

I think that's what I did, but I'm not sure if the numbers I used were right, do you remember what numbers you used for dy/dx?

Reply 4105

Sweatynerd

Original post by PythianLegume

Why, because I was confident on the paper? Someone has to do well.

Do your sweaty asian parents say they will burn your ball sack of if you dont excel in exams? Because i hope you fail massively and they burn your cock off too

Reply 4106

alow

Original post by NerdMeister

I think that's what I did, but I'm not sure if the numbers I used were right, do you remember what numbers you used for dy/dx?

I think mine were 3.25/75 or something close to that, got an answer of 0.04ish i think

Reply 4107

DudeBoy

Original post by otrivine

was the Ferrate, Feo4 2- ?

what was the equation for first one?

was it Fe +3/2cl2 --> FeCl3?

I did FeO3 :s-smilie:

Reply 4108

fayled

Original post by Jack9909

That was my train of thought, although I havent seen anyone who agrees yet!

Yeah somebody disagreed with me, and although I think I could counter their reasons why, I'm not too sure and can't be bothered now.

Reply 4109

otrivine

Original post by DudeBoy

I did FeO3 :s-smilie:

it has a -2 charge, this was a question from the stretch and challenge in book, it was FeO4 2-

Reply 4110

alow

Original post by DudeBoy

I did FeO3 :s-smilie:

Google Ferrate(VI), it is FeO4(2-)

(edited 10 years ago)

Reply 4111

Little Wing

Original post by NerdMeister

I think that's what I did, but I'm not sure if the numbers I used were right, do you remember what numbers you used for dy/dx?

Hmm, I just drew a tangent at t=40 and found the gradient :/

Reply 4112

Bradleya94

Anyone got a mark scheme yet? Starting to forget the questions

Reply 4113

needtosucceed=)

Original post by alow

Google Ferrate(VI), it is Fe2O4(2-)

the question told you it had an oxidation state of 6 (VI) therefore it has to be FeO4 2-

Reply 4114

keepontrying

what did people get for the equation for fecl3 reacting with water to form solution X?

Reply 4115

Crabbiey

Original post by Little Wing

Hmm, I just drew a tangent at t=40 and found the gradient :/

I'm afraid that's incorrect - that gives the initial rate of the reaction, not the rate of reaction after 40s.

I think I've lost 20-30 marks at least and am convinced I have an E or U (yes, I know that's extreme, but I've spent so long failing I kind of expect low grades. Seriously, I've struggled since primary school. So sorry if I'm being over dramatic). I just get this horrible feeling I've going to have history repeat itself on results day of failure...

Reply 4116

keepontrying

Original post by Benjy100

Are marks lost if I represented aluminium ethanoate like this ... Al(CH3COO-)3 with the minus sign there? Or do they overlook such things?

not sure now

Reply 4117

hussaincute

Original post by Crabbiey

I am afraid I feel the same way :frown:

I can understand how it feels

Reply 4118

FailedMyExams

Original post by Crabbiey

The initial rate would be a tangent at t=0

Reply 4119

MathsNerd1

Original post by Sweatynerd

Do your sweaty asian parents say they will burn your ball sack of if you dont excel in exams? Because i hope you fail massively and they burn your cock off too