ocr a f325 revision thread

I Should really get practising then! Cheers.

Thankfully my Chemistry Teacher has printed out 2 copies of all the past paper booklets for Chem 4 and 5. Printing in my school is so expensive.

If anyone has access to Chem 4 and 5 Jan 2013 please inbox me! Would be much appreciated!!!

Yeah I may have to! I'm intrigued :P
It's good that you didn't find it difficult, if we get a paper like that one in the summer that would be great
That does make sense! Fingers crossed :P

Funny seeing you here bro! OCR physics AND chemistry. We don't have it easy do we? lol

That would be insane! I think I'm gradually getting better after each paper I do, so will have to try my hardest to get near that.

Anyway yeah I did it as a mock, but not with my class. I just did it at home. I could hardly get it done in the time constraints and some of the questions took me ages to figure out, but it was my first past paper for F325. What about you?

oh I did at the time haha it was horrible, I died inside, but having done it and looking back it was hard, and more doable than I thought -yes some very hard bits, but most people could have got like 3/6 or 4/6 if you do working and remember the basic principles!

Hey, guys i'm also resitting this exam, i'm guessing the exam can't be any harder than January's so hoping for the best

I got 247 but a D in f324 so need to retake and aim for that A

I don't suppose someone could tell me what sodium thiosulphate does to iodine as I've seen it a large portion of questions and I'm still not quite sure what happens that we can observe :-/


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I remember seeing it in the textbook. can't remember at the top of my head. Glad you mentioned this, as looks like I'll need to cover it

Can anyone explain to me what happens at which terminal of a hydrogen-oxygen fuel cell when an alkaline electrolyte is used?

This is what I understand so far of what happens in a fuel cell with an acid electrolyte:
- At the anode the platinum catalyst splits the H2 into protons and electrons.
- The H+ crosses the electrolyte membrane, forcing the e- to travel around the circuit to the cathode (creating an electric current).
- At the cathode, O2 combines with the H+ from the anode and the e- from the circuit to make H2O.

So, at the anode: H2 --> 2H+ + 2e-
And at the cathode: 1/2O2 + 2H+ + 2e- --> H2O

Please please please help me I'm a little confused

Do we need to know what happens with an alkaline electrolyte? :-/

I'm not sure - but in the main OCR chemistry textbook they use an alkaline electrolyte as an example (but I didn't understand the explanation), and in the CGP textbook they use an acid electrolyte (which I understood). So do you think it's okay if we just know one or the other?

Hmm, if its in the textbook I'll say that there's a possibility of it appearing in the exam :-/

Also, does anyone have any advice/links that will help me understand how to write ionic equations and full equations? I know this is meant to be really basic stuff, but I still struggle and make little mistakes here and there... And I always seem to guess what state symbols to use! D: