1. lactate has a molecular weight of 90.08. How much lactate is needed to make 3 liters of .15 molar lactate.
2.What is the percentage of lactate (it's a solid) in the solution made in question 1.
1. How many mols do you need? That's mols = M x L = ?
Then mols = grams/molar mass. You know molar mass and mols from above, solve for grams.
2. You have mols/L and you know grams/L from 1. % w/v = grams/100 mL. Just change grams/L to grams/100 mL.