I'm currently working on the 'comparing methods for determining aspirin concentration' chemistry a2 investigation and have come across something which is seriously worrying me. I think i may have done the calculations for my colorimetry method wrong. could someone please just check these for me?
This is the procedure (shortened) relevant to the calculations:
50 cm3 volumetric flasks to store salicylic acid, maximum conc of aspirin being measured is 0.02 moldm-3 (in a 250 cm3 flask), so 50 cm3 of this will contain 0.001 moles right? if this is true then the maximum conc of salicylic acid needed should be 0.004 moldm-3 (0.001/250 x 1000) okay?
all the solutions were prepared with iron (iii) chloride, aspirin was hydrolysed etc and these were the results when the hydrolysed 0.02 moldm-3 aspirin and iron(iii) chloride absorbance was measured and plotted on the calibration curve:
absorbance reading: 0.49
concentration of salicylic acid (using calibration curve): 0.004 moldm-3
moles of sali acid: (0.004/1000) x 250 = 0.001
moles of aspirin (1:1 ratio) = 0.001
conc of aspirin: (0.001/50) x 1000 = 0.02 moldm-3
any help given will be greatly appreciated.
p.s. i would have asked my teacher but if the results are wrong then i will probably lie about them and i can't do that if my teacher has seen them.
Find out how.