[Kemistry12345]

Hi

A= e l c so c = A/el

Im trying to calculate the mass obtained from a reaction (9-hydroxyfluorenol to 9-fluorenone), from which a small sample, say 20mg, is used and diluted with 10cm^3 DCM in a volumetric flask, then used for a DCM solution cell IR (and then percentage yield calculated from the theoretical yield and this calculated mass)

The absorption on the IR is 0.18, and with the known value of el, c comes out at 1.90*10^-3 mol dm^-3

But now I'm supposed to use the exact mass used (20mg/0.020 g say) and consider the dilution of 10cm^3 to calculate the mass of fluorenone obtained from the reaction... ... ... But if a small sample was taken from the product synthesised (9-fluorenone), why not just weigh all of the product and then do a normal yield calculation (mass/theoretical yield)

Anyone got any clues?

Thanks

[mjc123]

Your product might be impure. If your absorption is measured at a wavelength where you can be sure it is only due to fluorenone, you have a measure of the actual amount of fluorenone present.
1.9*10^-3 mol/L works out at 3.42 mg in 10mL. So...

[Kemistry12345]

Your product might be impure. If your absorption is measured at a wavelength where you can be sure it is only due to fluorenone, you have a measure of the actual amount of fluorenone present.
1.9*10^-3 mol/L works out at 3.42 mg in 10mL. So...

Thanks

So if 3.42mg out of 20 mg used for the IR is actually fluorenone, then I have a percentage of the weighed product from the reaction that is actually fluorenone (17.1%) ?

So I can find 17.1% of the weighed product from the reaction, and that should be the mass of fluorenone... I hope