By William Adkins Updated Mar 24, 2022
A solution, or dilution, consists of a solid dissolved in a liquid solvent. Solutions are integral to medicine, industry, and everyday applications. Depending on the intended use, a solution’s concentration may be expressed as a mass ratio or volumetric ratio of solute to solvent. A molar solution specifically contains a defined number of moles of solute per liter of solvent. The following steps outline how to prepare a molar solution.
A mole is the amount of substance that contains 6.02 × 10²³ elementary entities, known as Avogadro’s number. This value was chosen because the mass in grams of one mole of a compound closely matches its molar mass. For example, one mole of water weighs approximately 18 g, matching the atomic weight of a water molecule. A molar solution contains a specific number of moles of solute per liter of solvent. The steps below assume you are preparing a 1‑liter solution.
Before adding the solvent, assess whether any exothermic, endothermic, or hazardous reactions may occur. Always use pure, analytical‑grade chemicals. For instance, use distilled water instead of tap water; tap water’s impurities can alter the solution’s chemistry.
Calculate the mass by multiplying the desired molarity (moles per liter) by the molar mass of the solute. Weigh the calculated amount on a calibrated analytical balance.
Place the weighed solid into a clean 1‑liter volumetric flask or jar. Add solvent gradually while stirring until the total volume reaches exactly 1 L. If the solute is slow to dissolve, gentle heating may help, but avoid exceeding the solubility limit.
Ensure your solution’s concentration is below the solubility limit. Precise measurements and awareness of potential reactions are crucial for a reliable molar solution.
