Question

A solution of ethanol water is prepared by dissolving 10ml ofethanol density 0.789g/mol in a 100ml of a solution with density 0.982g/mol.what is the cerntration of ethanol in the solution expressed in mass percent?;mass/volume percent?

Answer 1

mass ethanol=10*.789=7.89grams
mass solution=100*.982=98.2 grams

Mass percent= 7.89/98.2 x 100
mass volume= 7.89/100 g/ml, or7.89 %m/v
I dont know why a chem teacher is teaching mass/volume percents anymore, it is a misleading, confusing term, based solely on water dilute water solutions. This started in Biology circles, and they still use it, I think. In pharmacy, it is worse, they call it weight/volume percent, obviously not understanding the difference between weight and mass. At any rate, I do not understand why your teacher is giving this. I guess it is the same reason some still teach Esperanto....because a few folks use it.