You have available 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 prepare the following solutions? If the specific solution cannot be made, explain why not.

You have available 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 prepare the following solutions? If the specific solution cannot be made, explain why not.

**a. 10 mL of solution at 350 mg sugar per mL**

20% w/v stock solution = 0.2g/mL

10mL x 350mg/mL = 3500 mg = 3.5 g of sugar desired in our solution

then

volume of stock solution required = 3.5g / (0.2g/mL) = 17.5mL

my problem is, how can we create a 10 mL solution if we need 17.5 mL of it to have the right amount of sugar?

**b. 7 mL of solution containing micromoles of sugar.**

15umol ( 1mol/10^umol) = 1.5x10^-5mol

1.5 x 10^-5mol (160 Daltons / mol) = 2.4 x 10^-3g of sugar desired in our solution

again, how can we have a 7mL solution and have 2.4 x 10^-3g of sugar, since our %w/v for our stock solution is 0.2g/mL, 7mL will have 1.4g of sugar.

any help would be appreciated. thank you!