Mass of tobacco in a 25 mL aliquot from a 100 mL solution

[waqaszeb]

Hello,

If I get 2.0830 grams of tobacco and add 1 gram of barium hyrdoxide to it. Mix it in 100 mL of chloroform:toluene mixture, I essential have a 100 mL solution right? Now I take a 25 mL aliquote from that? what will be the mass in grams of tobaco in that 25 mL sample?

I thought simply 2.0830 x (25ml/100 mL) would do but my T.A. asked me to recalculate that because I did it wrong.

Thanks.

 

[Borek]

If you add these things to 100 mL of the solvent, you would have slightly more than 100 mL, so taking 25 mL would yield sample that is below 1/4 of the total. To be sure you can do it this way you would have to fill up to 100 mL with solvent.

I don't see a way to correctly estimate the sample mass with the data given, as the final volume is not known and impossible to calculate.