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OCR A2 Biology planning exercise!

Reply 180

urban_flavaz

yye but didnt u recieve an erratum notice? why wud they send that out?

Reply 181

myezza

Craghyrax

However, 1.5% solution in 200cm3 water works out to be 300mg aspirin which is roughly a tablet/ 1 dosage.

How do you work that out? What are your workings for that?

Reply 182

Talya

16

urban_flavaz

yye but didnt u recieve an erratum notice? why wud they send that out?

The erratum notic was because they said the aspirin in the wee was the thing reacting and it's not, it's salicylic acid. So they said you must include in your plan 'leave aspirin soln. for 24 hours to hydrolyse into salicylic acid' so your experiment works.

Reply 183

gdlil_indiangrl

craghrax!!! I LOVE U!...lol thank u so much!!
um one more question wot do we do about the colour of urine....use a yellow dye? or a yellow filter with the colorimeter?

Reply 184

gdlil_indiangrl

shud i mention how a colorimeter wrks in my introduction.....

Reply 185

Craghyrax

17

myezza

How do you work that out? What are your workings for that?

Someone earlier in the thread tipped me (sorry whoever it was.. don't feel like paging back), but they suggested that it was 1.5% aspirin in a 200cm3 volume water. 200ml is a normal cup size (so how much you'd dissolve a lemsip in) so its reasonable you'd figure out one aspirin dissolved in a cup. A normal aspirin dosage is 300mg. My maths was something like:
1.5/100 x 200 = 3
I multiplied 3 by 100. I assumed 200ml = 200g if weighed. I was able to use the same maths to figure out the mg in each of the amounts of aspirin solution I'd put into each tube. Eg: 2cm3 of 1.5% aspirin solution gave me (1.5/100x2 =0.03 x 100 = 3) 3mg of aspirin.
Someone correct me if I'm wrong!!! My maths is rubbish!!! :biggrin:

Reply 186

Craghyrax

17

Talya

The erratum notic was because they said the aspirin in the wee was the thing reacting and it's not, it's salicylic acid. So they said you must include in your plan 'leave aspirin soln. for 24 hours to hydrolyse into salicylic acid' so your experiment works.

Can someone tell me what the heck this 'erratum notice' is? I haven't seen hide nor hair of it. I've gone on the presumption that seeing as the question tells you you're PROVIDED with a 1.5% solution, that its been handed to you already hydrolysed. That's how I've got round it. Is that safe? What does everyone think? BTW even if you DID have to hydrolyse it, I personally think that it couldn't be as long as 12hrs you'd need, because that contradicts all the stuff I've read about aspirin. Aspirin is very water-soluble because it breaks down into ionic metabolites. If it took that long to hydrolyse then it wouldn't go so quick in the body.. or is my logic flawed? :confused:

Reply 187

Craghyrax

17

gdlil_indiangrl

shud i mention how a colorimeter wrks in my introduction.....

Its up to you.. I'm sure both are feasible (ways of doing stuff) but I'm using a filter for the colorimeter. I started with dye but changed my mind. And you don't need to waste any precious words on the colorimeter, just describe using it in your instructions in the method. That'll show them you know how it works.. your word count is precious.. use it for the theory.

Reply 188

sea tea

9

myezza

How do you work that out? What are your workings for that?

errrrm, Craghyrax's '3000mg normal dose' seems to be straight outta the euthanasia clinic.

normal aspirin dosage is 600mg, two 300mg tablets, not 3000mg, like somebody suggested earlier up.

we were told that 1.5% = 1.5g in 100cm³. drinking 200ml of 1.5% solution would therefore involve taking in far too much aspirin (3g, a massive overdose).

Reply 189

Talya

16

sea tea

errrrm, Craghyrax's '3000mg normal dose' seems to be straight outta the euthanasia clinic.

normal aspirin dosage is 600mg, two 300mg tablets, not 3000mg, like somebody suggested earlier up.

I think we can be surethat that was just a typo on her part. Above that she had wirrten 300mg so we can be sure that is what she meant.

Reply 190

Craghyrax

17

Talya

I think we can be surethat that was just a typo on her part. Above that she had wirrten 300mg so we can be sure that is what she meant.

Thanks!
It was a typo, but I'd be the least surprised person if my maths was flawed, trust me! :rolleyes:

Reply 191

Lalli

Can someone please give me a brief outline of the method for the expt ive been in hospital n missed the last week of college coz of it n missd out on lass min info :frown:

Reply 192

Talya

16

Lalli

Can someone please give me a brief outline of the method for the expt ive been in hospital n missed the last week of college coz of it n missd out on lass min info :frown:

There *are* brief outlines posted in this thread. Read.

Reply 193

paté

This is Biology so as far as we know what we are given is aspirin and not salicylic acid even tho anyone who is doing chem knows that aspirin will not turn iron(III)chloride purple.

Reply 194

La Trampa

18

paté

This is Biology so as far as we know what we are given is aspirin and not salicylic acid even tho anyone who is doing chem knows that aspirin will not turn iron(III)chloride purple.

well try writing aspirin as the reacting agent and we'll see what your score comes out as. i've checked biology books and they do mention it's slacylic acid.

Reply 195

elliebelly

wow that all took alot of reading, some helpful stuff tho. any advice going on how much detail one might be putting about preliminary work? ta x

Reply 196

paté

Think of it from the point of view of sum1 who is not doing chemistry it is unlikly that they know what Salicylic acid is so from this point of view it is a lot easier to think of it as aspirin even if it is not. Plus it wont actually change your estimate of the amount of aspirin left in the body. Also it would be wrong of the exam board to label a starting product as sumthing it is not if they were then going to dock marks for u assuming they were telling the truth.

Reply 197

La Trampa

18

paté

Think of it from the point of view of sum1 who is not doing chemistry it is unlikly that they know what Salicylic acid is so from this point of view it is a lot easier to think of it as aspirin even if it is not. Plus it wont actually change your estimate of the amount of aspirin left in the body. Also it would be wrong of the exam board to label a starting product as sumthing it is not if they were then going to dock marks for u assuming they were telling the truth.

they want you to research and on doing so,if you come across the fact that's it actually salicylic acid,and then miss it,doesn't make good scientific research does it? not on your part anyways. (not you personally by the way). anyways,you do as you please,it's your work,not mine. and i know loads of people who're not doing chemistry,and they told me,before i'd even checked it up,and they weren't in the slightless confused.

Reply 198

paté

So an exam board lying is fine so long as there is a posibility sum1 might realise?

Reply 199

Craghyrax

17

Knowing that salicylic acid reacts with FeCl3 is important, and is very obvious from even minimal research, but I also think that this planning project has potential to get far too chemical for biologists if we're not selective. I'm pretty annoyed at the misleading nature of the question myself! Don't get me started on OCR!!!

OCR A2 Biology planning exercise!

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