Answer
Molarity is a "method of convenience" when it comes to expressing solution concentrations because you don't have to measure solvent weights.
Work Step by Step
1. Solution concentrations can be presented in a variety of ways, from molarity and molality to w/v or v/v%. Each method has a different formula and different requirements.
2. In the case of molarity, all you need is the moles of the solute and the total volume of the solution. The first can be easily calculated through reactions if you couldn't measure the solute weight directly. The second can be calculated even more easily.
3. Because of these factors, it's very simple to find out the molarity and its variations (millimoles and so on) of any solution in laboratories, why it's referred to as the "method of convenience".
