Advanced higher chemistry aspirin investigation

Hi
For my chemistry investigation I am trying to find colorometrically the mass of aspirin in an aspirin tablet. I am at the very last stage but I don't know what to do next and my teachers have no idea either. I have the absorbance readings of the tablets and I am supposed to work out the mass from my calibration graph, which shows absorbance against concentration.
Anybody done this before?
Any help would be greatly appreciated because I am running out of time to get it done :eek3:

Reply 1

charco

Study Forum Helper

nasmith3

If you are at the very last stage then there isn't a next stage...

Reply 2

nasmith3

I mean its the last set of results that I need to calculate and therefore they are absolutely criticial to my investigation

Reply 3

GingerGoat

nasmith3

Well you can use the absorbance graph to work out the concentration. Then, assuming you know your total starting volume you can work out your number of moles.
n = cv/1000
then use m = no. of moles x formula mass of apsirin to find the mass :smile:

That make sense? apologies if a poor explanation :P:

Reply 4

nasmith3

GingerGoat

That make sense? apologies if a poor explanation :P:

That's the problem though, I don't have the total starting volume :s-smilie:

Reply 5

GingerGoat

ahhhh
then you cannot work it out.
So approximate, or make it up!

Measure the volume?

GingerGoat

ahhhh
then you cannot work it out.
So approximate, or make it up!

Can I really just make it up though?
The strange thing is there was someone at my school who did it a few years ago and I'm using their project as an example and they did everything the same as me and achieved similar results to my own but there is no sign of how she calculated the mass

Reply 8

nasmith3

Isn't there anybody who has done this before and can help me??

Reply 9

wanttoteach

They must have specified how they worked it out in their work.

Also your teachers should be able to help you.

As has been said if you dont have the starting volume I dont see any way for you to do it.

Reply 10

nasmith3

Ok thanks for your help. I have asked my teachers but they have absolutely no idea- I'm convinced they would fail the exam if they actually had to sit it.

Reply 11

miss_anomie

Hey, I know this was posted a while ago, but I'm having a brain fart of sorts and can't think how to calculate the concentratins of each standard to plot against absorbance on the standard curve. How is the concentration calculated? Any help you could give would me muchly appreciated :smile:

Reply 12

RobG93

Have you created a calibration curve using different concentrations of Salicylic acid (with FeCl3)?

Reply 13

gingerbreadman85

i'm guessing you dissolved the tablet in a large volume and then used a small amount of that solution to test?

Bets are you used a volumetric flask for that, so 250/500/1000ml. What solvent did you use? Aspirin isn't very soluble in water, so you'd need over 300ml to dissolve a 1g sample at room temp.

Can you work it backwards? If you know what mass you expected, then you can work out what volume gives you a reasonable figure.

Reply 14

sosh-teddy

, am a new user of the student room. Am here as well because of the investigations and yeah, applied for med and not heard anything positive yet but am not lettin my hopes down. Was thinking about doing something of Vit C but thought i could make that Vit A.. :rolleyes: