ocr a f325 revision thread

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Hahah glad someone gets the reference!!! We have someone who lifts on this Forum!

Just out of curiosity have you tried any of the questions yet? Sorry about my annotations on the questions as that helps me break it down into the trivial steps :smile:

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Reply 1281

Poffertje

I've just marked Q5a(ii) from jan 2012 paper and thought it to be straightforward but i have got my sign for Ni electrode wrong way round and don't understand why. I assumed that in Cell A the more positive electrode is the iron system so that gets reduced and will have negative sign so nickel will have positive.

(Sorry I haven't got electronic copy because I'm on phone!)

Thanks!

Reply 1282

Lehal

Original post by Myda

for Q5a) ii.. Cell A is based on redox system 1 and 2.. in order to determine the sign of the Ni electrode, u have to look at the electrode potentials.. Ni is -0.25 and Fe is 0.77.. so, the more negative electrode is oxidised, so, Ni has to be negative because it loses electrons.. Fe3+ is reduced as it gains the electrons.. simple mark.. just think about it.. it is pretty straightforward

Reply 1283

master y

Original post by MedMed12

anyone know what the highest an A has been and an A*? :smile:

84% = A* jan 12

Reply 1284

Dr00n

Original post by MathsNerd1

Here are the questions, I hope they are big enough to read. :smile:

ImageUploadedByStudent Room1370260723.349974.jpg

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Do you have answers to them?

Reply 1285

MathsNerd1

Original post by Dr00n

Do you have answers to them?

Oh yeah, I forgot to post them, sorry.

Here they are :smile:

Spoiler

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Reply 1286

MathsNerd1

Original post by MedMed12

any answers for those questions? :smile:

I've just posted the answers to those questions I posted earlier :smile:

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Reply 1287

Dr00n

are we supposed to know that HNO3 is an oxidising agent, because it makes sense but knowledge of it is news to me and we're a weekish away from the exam

Reply 1288

chignesh10

Original post by Dr00n

are we supposed to know that HNO3 is an oxidising agent, because it makes sense but knowledge of it is news to me and we're a weekish away from the exam

Don't think so!

Reply 1289

gingerninja22

Hi guys, I was wondering if someone could help me work out how to label conjugate acid-base pairs? I can't tell how you work out which one is A1 or B1 and why it matters the order of B1 and B2 etc. Hope that question made sense :colondollar:

thank you!

Reply 1290

MedMed12

Original post by MathsNerd1

Yeah, I'll post them when I get home tonight :smile:

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thank you

Original post by master y

84% = A* jan 12

Thanks

just hoping its not like the Jan paper tbh although overall it wasnt that bad, just nothing like before.

Original post by gingerninja22

thank you!

you can label the pairs either way round-doesn't matter which one is A or B but to work out what pairs with what, look at what is happening for example

CH3C00H +H20 ---> CH3COO- and H30+

CH3COOH has lost a proton -so it is a acid (acids are proton donors) and CH3COO- must therefore be a base- you can label that pair 1
H20 ---> gains a proton so is an acceptor (bases are proton acceptors) so is a base making H30+ an acid

hope this helps :smile:

Reply 1291

MedMed12

Original post by Dr00n

are we supposed to know that HNO3 is an oxidising agent, because it makes sense but knowledge of it is news to me and we're a weekish away from the exam

im sure they'd give it on context where you could work it out?

Reply 1292

MedMed12

Original post by zef1995

I agree, it was a challenging paper! You're welcome, I'm glad that I can help!
I'm guessing you've just done Jan 13 as a mock? You may have done better than you think! At least we have a difficult paper as a mock, it means we can see the type of stretch and challenge questions they can ask and learn how to tackle them :smile:

I hope your revision is going well!

I agree

Original post by Better

Just marked my Paper, here is my score Breakdown:

Total Score 77/100
Q1: 11/13
Two Elements that have atoms with two unpaired d electrons - Not so sure

Q2 - 10/11
Boom was so happy about this. The Mass is in fact the Net Mass
Forgot to put a -ve sign in front of my answer

Q3 - 15/16 - small error

Q4 5/10
Not sure about How to determine the initial rate?
I think I understand part c now.

Q5 - 7/10
ARGH, I tried to jump steps on the Equilibrium question, probably best to write things down explicitly

Q6 - 14/14

Q7 - 13/16
- Not sure about the full Ionic equation of Q7bii - Ca(HS03)2 OXIDISES Magnesium.. I think because there were two metals I was confused, could anyone explain this part?
- Got the Reaction of the Base wrong too.
- Question 7cii - Possible Equation - Got that wong apparently it was Benzoic Acid
- The last bit - I thought the rate of dissociation would be too slow so it would make a difference which apparently was wrong.

Q8- 2/10 :O :O :O :frown:

NOT sure whats going on :/ :/ :frown:

If that was the Jan paper then well done you!!

Reply 1293

gingerninja22

Original post by MedMed12

Thank you so much, yes it did! :smile:

Reply 1294

Funtry

Original post by Better

Just marked my Paper, here is my score Breakdown:

Total Score 77/100
Q1: 11/13
Two Elements that have atoms with two unpaired d electrons - Not so sure

It wants just two unpaired d electrons. Electron configurations work by having orbitals in pairs, but first each energy level is filled with one electron. So, as the EC of a transition metal is always (first row ones!) [Ar]4s^{2 (or 1 if copper/chromium)} then look for the two with 2 orbitals with 1 electrons. This will be

Spoiler

. Hope that makes sense

Q2 - 10/11
Boom was so happy about this. The Mass is in fact the Net Mass
Forgot to put a -ve sign in front of my answer

Q3 - 15/16 - small error

Q4 5/10
Not sure about How to determine the initial rate?
I think I understand part c now.

Clock reactions etc, so a sudden change. You would add a

Spoiler

Q5 - 7/10
ARGH, I tried to jump steps on the Equilibrium question, probably best to write things down explicitly

Q6 - 14/14

Q7 - 13/16
- Not sure about the full Ionic equation of Q7bii - Ca(HS03)2 OXIDISES Magnesium.. I think because there were two metals I was confused, could anyone explain this part?
- Got the Reaction of the Base wrong too.
- Question 7cii - Possible Equation - Got that wong apparently it was Benzoic Acid
- The last bit - I thought the rate of dissociation would be too slow so it would make a difference which apparently was wrong.

Q8- 2/10 :O :O :O :frown:

NOT sure whats going on :/ :/ :frown:

I could put my answer for this on a photocopy up, but I'm not sure where it is?

Spoiler

Put what I've answered above, italicised the questions I have. All of these are done from memory, so there may be some errors.

Reply 1295

chignesh10

Original post by Funtry

Put what I've answered above, italicised the questions I have. All of these are done from memory, so there may be some errors.

Hi, how are you preparing for this exam?
Have you done all the papers? What else are you doing....need to know how future imperial chemists work :wink:

Reply 1296

username938518

After quite a lot of revision I am just getting into the A boundary in the past papers. I have a week to make this a definite comfortable A. This paper is going to be the death of me.

Reply 1297

Better

Original post by Funtry

Put what I've answered above, italicised the questions I have. All of these are done from memory, so there may be some errors.

Thanks Funtry! Yes I went over Question 8 with my Teacher, in some ways it was actually easier than the Previous years, because you only really had to create 1 Equation, and then just do Maths rather than create like 3-4 equations.

If you have any tips on those Equations I got wrong though please advise..

My Teacher said this: "the mistakes you made are only mistakes that aren't really on the syllabus, even if you had another 3 months we wouldn't cover this, a lot of it, is really just working through it like a puzzle from fundamentals"

Can you explain your type of mindset when your doing the Chem Questions? Think this is what I really must nail then in the next few days to be at a Peak and have what the Examiners reports described as a "Chemical Flair"

(edited 10 years ago)

Reply 1298

Better

Original post by MathsNerd1

Just out of curiosity have you tried any of the questions yet? Sorry about my annotations on the questions as that helps me break it down into the trivial steps :smile:

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Apologies MathsNerd not yet!

Today is my Maths and Physics day; tomorrow is Chemistry and Maths so I will be BLITZING the Chemistry questions! I'll do

1. The Questions you put up
2. Specimen Paper or June 2011

then Chem 4 stuff...The Boundaries are so tight there is pretty much no room for Error in Chem 4 :/