What is the percent by volume concentration of a solution containing 300.mL of isopropyl alcohol and enough water to give 400.ml of solution?Which component is the solute and which is the solvent?

Answer 1

Actually it makes little difference which we call the solute and which the solvent; however, usually we assign the solute to the smaller quantity and the solvent to the larger number. Or if solid/liquid, we usually call the solute the solid and the solvent the liquid. In the case of solutions of two liquids that are about 50%, the assignment often is arbitrary.
In this case I would assign isopropyl alcohol as the solute (even though it is the larger quantity) because the problem states the known quantity of alcohol as 300 mL (and the quantity of water is not known) so % alcohol = (300/400)*100 = 75% v/v. If you say it that way (75% alcohol v/v) you know the alcohol has been assigned as the solute and water as the solvent.