What does it mean when you have a dilution problem whos volumes are additive? For instance, What is the concentration (Molarity) of the solution made by diluting 25.0 mL of 3.00 M HCl with 75.0 mL of water? (Assuming that volumes are additive.)I know that this is an M1V1 M2V2 problem, but does this mean that the volumes must be added, or that they have already been added and I can proceed with the problem?
The phrase assume volumes are additive means that the problem wants you to assume that when you add 75ml water to 25ml 3M HCl you end up with 100ml of solution. This may seem silly, but in reality, you will probably end up with some volume less than 100 (albeit a very small amount less) since the HCl in solution affects the density and will result in a slightly different volume. The qualifying phrase simplifies the math for the problem. If you use your equation M1V1 M2V2, M1 3, V1 25. V2 100, and solve for M2.
