OCR A2 Biology planning exercise!

we're giving all the answers! some hard work people! :p:

ok just write that aspirin is used for pain relief etc etc and when you ingest it,some of it goes and acts in the body and the rest comes out in urine,ultrafiltration etc etc. and by calculating how much you have in the urine,you can calculate the concentration left in the body. etc etc.

Reply 44

so_this_is_sam

3

think i must be doing the coursework instead. if you are doing a practical exam now does that mean you have three bio exams in the summer not inc retakes? because im on ocr board and ive got 2 exams not inc practical

Reply 45

we're not doing the practical,it's like...planning for the practical.we're still doing the practicals plus the other exams.

Reply 46

I'm a bit confused...

We're given a 1.5% solution, but how do we know what the exact amount od aspirin is in it if we don't know the volume of the solution??

Therefore, when the urine sample is tested, the aspirin concentration can only be given as a %. Or is that what we are aiming for?

I'm sorry if that doesn't make sense...I know what I mean to ask but can't say it in nice English!

Reply 47

er...i'm a bit confused.

the conc can always be 1.5% if it's 1cm3 of liquid or 100cm3 of liquid. you're supposed to find out how much is in it by using the Fe solution.that's what the whole experiment is about.

when you get the perecentage,you read off the concentration from the calibration curve and then you'll be able to calculate what's left in the body

Reply 48

But when doing the calibration curve, you can only record the absorbance against a % concentration for the graph. You can only then state a % of aspirin in the urine....so how do you work out how much aspirin is in the urine (rather than a percentage) to then calculate what is left in the body?

Reply 49

if you know how much is going in,and you know how much is left,do you think you can calculate it now?

original - final = conc. left in body.

Reply 50

I don't know how much I have, that's was my initial question.

I only know I have a concentration of 1.5%. I don't know if that's 1 gram in lots of water or 0.5 grams in half as much water.

I really am rubbish at gettin my point across... Thank you for trying to help though.

Reply 51

no no no. you do know,because when you get an aspirin pill,the concentration is given.just get any pack of aspirin and look at the back.

Reply 52

So, i'm making the solution myslef with as much water as I choose? I think I understand. My teacher stared blankly when I asked... Thanks muchly!!

np.

Hey there,
This is a VERY cheeky post but I'm doing A2 OCR Bio and we haven't had the planning exercise yet. I know that some may see this as me having an unfair advantage but any help, hints or info about the question would be MASSIVELY appreciated. I can always try my best to help with any questions others may have if I'm clued in....! :rolleyes:

Reply 55

well try reading the whole post first,then the other one in the other thread about the same topic as well :wink:

there's a good start

Reply 56

igloo

1

Sorry but could someone possibly explain what we're meant to do in this experiment=> clearly.
- Plus is the pH just given as a variable that could affect the aspirin conc. in the 'urine,' i.e we are just expected to be aware of it, or do we have to actually use diff. pHs in the expt. and observe their affect.

Reply 57

i'm not sure but i haven't tried changing the pH,but according to the question,it might havean effect yes

Reply 58

currentlystruggling

Hello! I did the trial thingy the other day and made the calibration curve up etc. A lot of people in my biol got the results the wrong way round, so that less aspirin=more purple. It didn't matter though.
Anyway my teacher reckons the ph thing is a red herring and that we should only refer to it in background knowledge.
Also it isn't as simple as knowing how much went in, how much came out and then knowing how much is left in the body cos some aspirin gets decomposed in the stomach to form other compounds like salicylic acid.

Reply 59