Molarity

In a solution, the solute is the smaller portion that is being dissolved by the solvent, the larger portion usually in the form of H2O. Molarity is the term used to describe the solubility of the solute within the solvent. 

Molarity Formula 

Molarity serves as the bridge between moles and volume. It is the concentration of a solution represented as moles of solute per liter of solution: 

mol/l-w/vMolarity Formula

This would mean a solution that is 0.10 M NaCl: 

Understanding-MolarityUnderstanding Molarity

Although moles per liter are the traditional units for molarity, you can also use mg/mL because it is proportionally equivalent. 

Molarity Calculations

From the molarity formula, you can calculate volume, grams or the moles of solute. 

To calculate molarity from mass (in grams, milligrams, etc.) and volume (milliliters, liters, microliters, etc.): 

Molarity-from-mass-volumeMolarity from mass and volume

To calculate the mass from volume and concentration: 

Mass-volume-concentrationMass from volume and concentration

To calculate the volume from mass and concentration: 

Volume-from-mass-concentrationVolume from mass and concentration

Osmolarity

Ionic molarity or osmolarity represents the molarity of dissolved ions in a solution. For example, if you were asked how to calculate the osmolarity of 0.200 M KNO3

STEP 1: Break the ionic compound into ions. 

Dissolution-Ionic-CompoundDissolution of KNO3

STEP 2: Now calculate the osmolarity of the solution with its equation. 

OsmolarityOsmolarity

Dilutions

Another common idea related to molarity deals with the dilution of stock solutions. In a dilution a concentrated solution is made more diluted by adding water.

Dilution-EquationDilution Equation

After Molarity 

Eventually you will do calculations that connect molarity to problems with density, molarity vs molality, mole fraction, mass fraction or percent


Beyond these calculations that deal directly with the molarity formula you can bring in stoichiometry. This brings in more complex problems dealing with solution chemistry, acid base titration, pH and pOH