Parts per million (ppm) and molarity are two units of measurement used to describe the concentration of a chemical solution.

PPM represents the number of molecules of solute per million parts of a solution. It is calculated as the ratio of the mass of the solute to the mass of the solution, multiplied by one million. It is usually expressed in units of mg/L or μg/mL.

Molarity is a measure of the number of molecules or ions of the solute present in a given volume of the solution. The molarity of a solution is calculated by dividing the number of moles of solute by the volume of the solution in liters. In chemistry, molarity is commonly used to prepare solutions of specific concentrations for various reactions and experiments. It is expressed in units of mol/L or M.

In some cases, it may be necessary to convert between PPM and molarity in order to compare different types of solutions or to carry out calculations in chemical reactions.