chemistry! URGENT
posted by Lindsay on .
A standard solution is prepared for the analysis of fluoxymesterone (C20H29FO3), an anabolic steroid. A stock solution is first prepared by dissolving 10.0 mg of fluoxymestrone in enough water to give a total volume of 500.0 ml. A 100.0 micro liter 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.
Please show all steps because I actually understand and learn how to do this. Thanks!

We need the molarity so we will need to be working in moles and therefore need the molar mass of the steroid.
I make this
C. 12 x 20 = 240
H. 29 x 1 = 29
F. 19 x 1 = 19
O. 3 x 16 = 48
total = 336 i.e. 336 g mol^1
If 10.0 mg is dissolved taken then this is
0.0100 g /336 g mol^1
= 2.98 x 10^5 mol
If this is dissolved in 500 ml which is 0.500 L then the concentration is
2.98 x 10^5 mol / 0.500 L
= 5.95 x 10^5 M
If 100 microlitre (0.100 ml) is diluted to 100 ml then this is a 1000x dilution (100 ml / 0.100 ml = 1000) so the final solution will be 1000 x more dilute. so
5.95 x 10^5 M /1000
= 5.95 x 10^8 M
(please check the maths, and you will need to decide on the final sig figs, which will be 3 sig figs I think) 
Thank you! That was a giant help, I understand now!