# chemistry! URGENT

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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!

• chemistry! URGENT - ,

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)

• chemistry! URGENT - ,

Thank you! That was a giant help, I understand now!