you need 25g of glucose. you are given a 5% (w/v glucose solution. ho many mL of the 5% glucose solution do you need to obtain 25g of glucose?

Question

I'm not sure which formula to use for this problem: (concentration 1)(volume 1)=(concentration 2)(volume 2) or%(weight/volume)=(#grams of solute/ #milimeters total volume of solution)*100

Answer 1

You should try to get away from memorizing and using certain formulas and start to “understand“ the question. So here, we have a 5% w/v solution of gluc. That translates to 5 g glucose/100 ml of solution. This means you have 0.05 g glucose/ml. So all you have to do is set up the relationship of how many mls of this solution will give you 25 g og glucose. You can solve this mathematically as follows:

(x ml)(0.05 g/ml) = 25g

x = 25/0.05

x = 500 ml

if you approach each problem this way, you don’t have to memorize any formulae.