Posted by mel on .
A standard solution is prepared for the analysis of fluoxymesterone (C20H29FO3), an anabolic steroid. A stock solution is first prepared by dissolving 13.0 mg of fluoxymesterone in enough water to give a total volume of 500.0 mL. A 100.0 µL aliquot (portion) of this solution is diluted to a final volume of 100.0 mL. Calculate the concentration of the final solution in terms of molarity.

chem 
DrBob222,
To make things easier (on me to type) let's call fluoxymesterone just FLM.
13.0 x 10^3 g FLM/500 mL = xx g FLM/mL.
That is the stock solution.
It is diluted 100.0 microliters to 100.0 mL. So the new solution is
xx g FLM/mL x (100.0 x 10^3 mL/100.0 mL) = yy g FLM/mL.
To find the molarity just multiply
yy g FLM/mL x 1000 mL = zz g FLM/L.
zz g FLM/molar mass FLM = mols and this is molarity since this is # mols in 1 L.
Check my thinking. Check my work. Watch the units. Make sure I made the conversions properly.