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

Question

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

DrBob222 · Accepted Answer

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.