chemsitry
posted by allen on .
Calculate the mass in grams of sodium bromide, NaBr, are needed to prepare 250.0 mL of a solution of sodium bromide that is 3.50% (m/v).

3.50% m/v means 3.50 grams NaBr/100 mL soln. You can do this one of two ways (They really are the same but the look is different.)
3.50 x (250/100) = ??
or
(Xg/250 mL)*100 = 3.50 and solve for X.