Hello, I have a question that is related to % w/v. The question is as follows:
You have a 20% w/v stock solution of a sugar of molecular weight 160 Daltons. How much of this stock solution will you need to use to...
a. prepare 10 ml of solution at 350 mg sugar per ml.
So 20% w/v stock solution = 0.2 g/mL
350 mg/mL x 10mL gives us 3500mg of the sugar, or 3.5g
so the amount of solution we want is
x mL = 3.5 g / (0.2g / mL) = 17.5mL ( is this correct?)
b. 7 ml of solution containing 15 micromoles of sugar
15umol = 1.5 x 10^-5 mol
1.5 x 10^-5 mol (160 Daltons / 1mol) = 2.4 x 10^-3 g
(2.4 x 10^-3g) / 7mL = 4.89 x 10^-5 g/mL
and then I am stuck. How are you supposed to make 4.89 x 10^-5g/mL solution from a 0.2g/mL stock solution?! Is it possible? it does say in the question If the specific solution cannot be made, explain why not.
thank you in advance!