A solution is a homogeneous mixture of two or more substances. The major component in the mixture is the solvent; the minor component is the solute. An aqueous solution has water for the solvent. We can talk about relative amounts of solute in general terms. If we have very little solute, it is a dilute solution. If we have relatively large amounts of solute, it is a concentrated solution. We also have ways to calculate solution concentration to quantitatively represent how much solute is present. There are many different units for solution concentration. We'll start by discussing molarity, which is moles of solute divided by liters of solution. Let's practice with this concentration unit. Our problem reads, "Calculate the molarity for a solution where you dissolve 50 g of calcium nitrate in enough water to make 2 liters of solution." We'll start with our equation for molarity. In the problem, we're given grams of calcium nitrate, which is our solute, so we need to convert from grams to moles. Using dimensional analysis, 50 g of calcium nitrate is converted into moles using its molar mass, which is 161.1 g calcium nitrate per one mole. So we have 0.3047 moles of calcium nitrate. Plugging this back into our equation for molarity, these moles of calcium nitrate are dissolved in enough water to make 2 liters of solution. Completing the calculation, we get 0.152 molar calcium nitrate. The units of molarity are molar and are represented using a capital M. The problem we worked was worded very carefully. In the problem, we added enough water to make two liters of solution; we did not add two liters of water. The way we prepare a solution with a particular molarity is a consequence of how the unit is designed. If we want to make one liter of a one molar sodium chloride solution, we would first measure out one mole of sodium chloride, which is 58.44 grams. Then we would add enough water to completely dissolve the sodium chloride. Then we would add enough water to bring this solution up to one liter. The result would be one liter of exactly one molar sodium chloride solution.