Molarity

Molarity (M) is a term used in chemistry to indicate the concentration of a solute in a solvent, in units of M = moles/liter. For a pure compound with virtually no solvent, molarities are in the range of about 10-18 M. Chemical solutions typically used in labs are often between 10 millimolar (mM) and 1 molar concentrations. Solutions of biological samples, containing proteins, enzymes or DNA, are more oftenly used in the nanomolar (10-9 M) or micromolar (10-6 M) range, up to about 10 mM. For a solution containing many molecules, each molecule will have a molarity which is independent of the other components, unless they chemically react over time. Molarity is calculated by dividing the amount (mass) of the chemical being added into a solution by both its molecular mass (molecular weight MW) and the final volume of the solution.


 * $$ M = \frac{moles}{liter} = \frac{m}{MW*V}$$

where
 * m = mass of chemical added, in grams


 * MW = molecular weight (mass), in grams/mole


 * V = final volume of the solution