When dealing with solutions, the amount of solute dissolved in the solvent is measured as the concentration of the solution. Concentration can be measured in one of several units: molarity, mass concentration, molality, mole fraction, percent mass, parts per million, or normality.
Molarity is defined as moles of solute per liter of solution. Mass concentration is the mass of solute per liter of solution. Molality is defined as moles of solute per kilogram of solvent. The mole fraction of solute is the ratio of the moles of solute to the total moles present in the solution. The percent mass describes what percentage of the total mass of the solution the mass of the solute represents. Measurements in parts per million describe the number of particles of solute present in every million particles of solution. In finding the normality of a solution, the grams of solute are first converted to moles. The moles of solute contain equivalents of the elements comprising the solute. The number of equivalents of an element is equal to the number of atoms of that element present in the molecular formula for the solute. For example, one mole of contains two equivalents of protons.
