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OCR A2 Biology planning exercise!

Reply 380

Rastnim

How would one go about including the calibration curve thing?

Reply 381

waseemhassam

Rastnim

How would one go about including the calibration curve thing?

well i have discussed a worked example of how you would use a sample and add Fecl3 and then use the colorimeter to get a value and then see the value absorbtion to concenrtration using the line of best fit made by the calabration curve

please pm your conc details and how you went about it

cheers

Reply 382

matt9999999999

Ok this is when i ask the stupid question.....but what is a calibration curve? is it just concentration(x axis) plotted against whatever value the colourimeter gives (y axis) ????

sorry to be a pain and stupid!

Reply 383

matt9999999999

Ok this is when i ask the stupid question.....but what is a calibration curve? is it just concentration(x axis) plotted against whatever value the colourimeter gives (y axis) ????

sorry to be a pain and stupid!

Reply 384

Talya

16

waseemhassam

please give me a breif idea

No! Please do some work yourself.

Do you think the amount of concentrations you have chosen will give you an accurate graph to use? I, personally, have tried to make it as accurate as possible, because I don't actually have to do it, it is just a plan.

Reply 385

matt9999999999

Talya

No! Please do some work yourself.

Do you think the amount of concentrations you have chosen will give you an accurate graph to use? I, personally, have tried to make it as accurate as possible, because I don't actually have to do it, it is just a plan.

Well u do have to do it though, for the preliminary work....wouldnt be a bad idea really would it?

Reply 386

tozhan

ok here it goes:

high concentration of aspirin solution = darker purple colouration
low concentration = lighter purple

if you got orange you didnt add any aspirin (or it isnt hydrolysed)

if it didnt hydrolyse you add a small quantity of HCl

ignore pH in the experiment planning. ONLY write about its effects in your introduction.

now im late for college, tchuss!

Reply 387

gdlil_indiangrl

this planning exercise is in for today in a couple of hrs...can i PLEASE just ask....apparently im only allowed one colour filter....which colour filter do i use with what...do i use a blue filter with my yellow solution or a yellow/green filter with my aspirin solution!!!

Reply 388

Talya

16

matt9999999999

Well u do have to do it though, for the preliminary work....wouldnt be a bad idea really would it?

You don't HAVE to do preliminary work. We aren't.

Reply 389

police

You don't HAVE to do preliminary work. We aren't.

tayla

how come?

Reply 390

Talya

16

suzukiescudo

tayla

how come?

It's a plan. Perhaps in your method you could write 'For preliminary work.. do this'

As far as I'm aware it's not a necessity.

Reply 391

waseemhassam

gdlil_indiangrl

this planning exercise is in for today in a couple of hrs...can i PLEASE just ask....apparently im only allowed one colour filter....which colour filter do i use with what...do i use a blue filter with my yellow solution or a yellow/green filter with my aspirin solution!!!

the filter must contrast the purple my teacher indicated to me that i should use a green filter

Reply 392

Talya

16

waseemhassam

the filter must contrast the purple my teacher indicated to me that i should use a green filter

I've said you needed a purple filter to allow only the purple light from the product through. Is this wrong?

Reply 393

tulip13

Talya

I've said you needed a purple filter to allow only the purple light from the product through. Is this wrong?

yes it is wrong. u have to use a complimetary coloured filter

Reply 394

police

i did the exp again and the orange colour never came up. yipee!!!

thank god.

high conc of asprin=Dark puple
gradually the lower the conc of asprin= lighter the purple colour.
low conc of asprin= lilac colour but lighter.

now when i put it in the caloremetar (cant spell) i got the %thingy.
now how do i plot out the calibration curve?

Reply 395

tozhan

Talya

It's a plan. Perhaps in your method you could write 'For preliminary work.. do this'

As far as I'm aware it's not a necessity.

your correct, preliminary work is not required and full marks are available to those who dont do it. BUT, it is much easier to get marks if you demonstrate WHY you choose a certain filter or WHY you did such and such. Preliminary work is a good way to demonstrate this.

Also every experiment in a proffessional environment should have prelim work to find the most effective/effcient/correct method. Espeically if the experiment hasnt been tried before!

I would suggest to all who have access to a lab that prelim work is a good idea. If you dont have access or your teacher doesnt want to touching his new test tubes or whatever, dont worry! its ok not to run prelim tests.

Reply 396

Talya

16

tulip13

yes it is wrong. u have to use a complimetary coloured filter

Complimentary to what? The urine? In which case, it's still purple!

Reply 397

waseemhassam

tozhan

your correct, preliminary work is not required and full marks are available to those who dont do it. BUT, it is much easier to get marks if you demonstrate WHY you choose a certain filter or WHY you did such and such. Preliminary work is a good way to demonstrate this.

Also every experiment in a proffessional environment should have prelim work to find the most effective/effcient/correct method. Espeically if the experiment hasnt been tried before!

I would suggest to all who have access to a lab that prelim work is a good idea. If you dont have access or your teacher doesnt want to touching his new test tubes or whatever, dont worry! its ok not to run prelim tests.

2day i had done my prelimanary work

here are my findings
when Fecl3 is added only a couple of drops are needed otherwise the whole solution become dark puple inc diluted ones

the different concentrations must be very different my range using different amounts of purified water but kept the amount of aspirin same

the filter needed must be a complementary as the different colours i saw today were ranging from blood red to purplish and light violet so the filter must be a colour that absorbs all colours and reflects a colour that i did not see and therefore green was the best filter

please pm me if u want to know more

thanks

sorry tayla i was being selfish

Reply 398

Talya

16

I was PMed by waseemhassam saying I shouldn't use a purple filter, I should use green.

But surely i want to use purple because I only want the purple wavelength to be detected by the colorimeter, I want all other wavelengths to be blocked, right?

Reply 399

tozhan

Talya

I was PMed by waseemhassam saying I shouldn't use a purple filter, I should use green.

But surely i want to use purple because I only want the purple wavelength to be detected by the colorimeter, I want all other wavelengths to be blocked, right?

well this is where i have to admit a little problem with my planning...

basically the whole idea is that you use a complimentry filter (means the colour being absorbed)

So if the solution goes purple, you should use green/yellow filter.

BUT, i found in my prelim that yellow filter gave me erroneous results. So i ended up using violet (430nm) as this gave me good results.

i dont remember how i justified this. think i just said that yellow filter didnt work. not the most scientific. dont really care. only 14 marks.

THIS IS WHY YOU SHOULD DO PRELIMINARY WORK!!

OCR A2 Biology planning exercise!

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