chemistry
posted by Heather on .
A student placed 19.0g of glucose (c6h12o6) in a volumetric flask, added enough water to dissolve the glucose by swirling, then carefully added additional water until the 100ml. mark on the neck of the flask was reached. The flask was then shaken until the solution was uniform. A 20.0ml sample of this glucose solution was diluted to 0.500L . How many grams of glucose are in 100ml. of the final solution

So we have prepared 19.0 g glucose in 100 mL. We now have a 19/100 = 0.19 g/mL (that is, 0.19 g glucose per mL solution).
We take a 20 mL sample of that and place a container. How many g glucose did we transfer? We transferred 0.19 g/mL x 20 mL = 3.8 g to the container. Now we dilute that to 500 mL so we now have a solution that contains 3.8 g in 500 mL. That is 3.8/500 = 0.0076 g/mL and if we take 100 mL of that sample we will have
0.0076 x 100 mL = 0.76 grams glucose. Check my arithmetic.