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.
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.
To calculate the concentration of the final solution in terms of molarity, you will need to know the amount of fluoxymesterone present in the final solution and the final volume of the solution.
Given information:
- Stock solution volume: 500.0 mL
- Mass of fluoxymesterone in stock solution: 13.0 mg
- Volume of aliquot taken: 100.0 µL
- Final volume after dilution: 100.0 mL
First, let's calculate the concentration of fluoxymesterone in the stock solution.
1. Convert the mass of fluoxymesterone to moles:
Molecular weight of fluoxymesterone (C20H29FO3) = (12.01*20) + (1.01*29) + (19.00*1) + (16.00*3) = 376.50 g/mol
Moles of fluoxymesterone = 13.0 mg / 376.50 g/mol = 0.0345 mol
2. Calculate the molarity of the stock solution:
Molarity = Moles of solute / Volume of solution (in liters)
Stock solution volume in liters = 500.0 mL / 1000 = 0.500 L
Molarity = 0.0345 mol / 0.500 L = 0.0690 M
Now, let's calculate the concentration of the final solution after dilution.
3. Calculate the moles of fluoxymesterone in the aliquot:
Moles of fluoxymesterone in aliquot = Molarity * Volume of aliquot (in liters)
Volume of aliquot in liters = 100.0 µL / 1000 = 0.0001 L
Moles of fluoxymesterone in aliquot = 0.0690 M * 0.0001 L = 6.90 x 10^-6 mol
4. Calculate the concentration of the final solution:
Molarity = Moles of solute / Volume of solution (in liters)
Final volume after dilution in liters = 100.0 mL / 1000 = 0.100 L
Molarity = (6.90 x 10^-6 mol) / (0.100 L) = 6.90 x 10^-5 M
Therefore, the concentration of the final solution in terms of molarity is 6.90 x 10^-5 M.