ocr a f325 revision thread

Quick question:

Cr2O7^(2-) + 14H^(+) + 8e^(-) ---> 2Cr^(2+) + 7H2O
Oxidation for Cr: +6 ----> +2

How comes its 8e^(-)?
From the oxidation number I would have thought it would be 4e^(-).
I'm I missing something in this whole idea? This is the answer for a question btw. This was the answer from the MS.
I am so confused, just when I thought I was good at these. ¬_¬

What drugs are you taking?

any else not doing papers yet, as there is only 5 and doing question packs?

What question packs are you using? I've done all the past papers... :L

my teacher gave us these packs of about 100 pages of questions about 60 questions maybe and so im doing them first before doing the 5 past papers which ill do from fri to sun.

Could I possibly have some of those please?

my teacher gave us these packs of about 100 pages of questions about 60 questions maybe and so im doing them first before doing the 5 past papers which ill do from fri to sun.

I would like a copy if you can find one, I'm sure they must have an online copy that could be uploaded to help Just out of curiosity what do these questions cover? Is it all the different parts of the unit or just specific ones?


Posted from TSR Mobile

sure ill post them on here once ive found them or i can send an email to ask
whole specification-mixed
but there are some 'class assessments' and 'mixed questions booklets for each modules which we were given too earlier in the year.

Thanks and wow, you've been given a lot of preparation stuff for this exam, my school doesn't really do anything extra, just past papers really

I'll be winging this exam slightly as I've not been completely prepped for it :-/


Posted from TSR Mobile

hmm we dont get given past papers though -she used to print them
the question booklets we were given ages ago were all the relevant old spec questions and some extra sheets from this chemistry book she has
the massive pack of 60 questions, I think were brought from a company
only started chem today too :/

hello

could anyone please explain to me how to work out the rate-determining step...I cant seem to get my head around it

hello

could anyone please explain to me how to work out the rate-determining step...I cant seem to get my head around it

hey

basically write out what is in the rate equation as the start of line one


leave some space and write out the full equation
then its abit of trial and error/playing around to find things which equal same amount on left and right side as final equation

videos on youtube are good for this

hey

basically write out what is in the rate equation as the start of line one


leave some space and write out the full equation
then its abit of trial and error/playing around to find things which equal same amount on left and right side as final equation

videos on youtube are good for this

thanks I will have a look on youtube then