Need help working at a concentration in mmol/l! Thanks?

Question

i put 104 microlitres of propofol at 97% into 100ml. i believe that made me a 1% solution (lab techs workings). the propofol came in a 100ml solution from sigma aldrich.

link:http://www.sigmaaldrich.com/catalog/search/ProductDetail/ALDRICH/D126608

Thanks!

sorry i ment 0.1%

Answer 1

Basically, you convert the volume 104 microliters (0.104 mL) into moles. To do this, you need the density (0.962 g/mL) and molecular weight (178.27 g/mol) which are provided in your link.

Volume x density gives 0.10 grams in 104 microliters. Dividing # grams by molecular weight gives 0.00056 moles or 0.56 mmol. Divide mmol by volume (100mL = 0.1 L), gives 5.6 mmol/L. If you want to take into account that the propofol is 97%, multiply by 0.97 to get 5.43 mmol/L.

These calculation are extremely basic and can be applied to all compounds. When in doubt, look at the units you need and work backwards.

The answer above doesn't take density into account. His method is used for calculating the concentration of a solution when you are diluting another solution in which the concentration is known (e.g. if you put 10 mL of 12M HCl into 100 mL, what is the final concentration). His # is close (lucky) because the density is close to the purity. If the density was something like 1.3 g/mL, his answer would be way off. The added volume of 0.104 mL is negligible in this case (rounding up to liters).

Answer 2

Use the C1V1=C2V2 equation, making sure that you use the same units for C1, C2. Then it doesn't matter if it is molarity, molality, % or whatever. Similarly V1, V2 must have the same units (regardless of what C has). Any conversion factor is simplified in this equation.

you put 0.104 mL of 97% into 100 mL (thus V2=100.104)
C2=(V1/V2)*C1= (0.104/100.104)*97 =0.1%

So yes, you have made 0.1% solution.
According to the link propofol has MW=178.27, so you have prepared a 0.1*10/178.27 =0.005609 =0.00561 M =5.61 mM or 5.61 mmole/L solution

Answer 3

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