Concentration

Concentration is the amount of a substance present in a specified volume or mass of a mixture. It can be expressed in several units, depending on how the amount and mixture are measured.

Amount of substance: A measure of how many elementary entities, such as atoms or molecules, are present. Concentration can count particles through the mole rather than weigh them directly.
Molar concentration: The amount of solute, in moles, per unit volume of solution. It is the standard volume-based expression for dissolved chemical substances.
Dilution: The reduction of a solution's concentration by adding solvent or otherwise increasing its volume. Dilution changes concentration while leaving the amount of solute unchanged.
Molarity: The number of moles of solute per liter of solution. It is often used as a synonym for molar concentration, but names a specific unit convention.
Diffusion: The net movement of particles from regions of higher concentration to regions of lower concentration. A concentration gradient drives diffusion until the gradient diminishes.
Mole: The SI unit for amount of substance, defined by a fixed number of elementary entities. Molar concentration uses moles of solute as its numerator.
Molality: The amount of solute in moles per kilogram of solvent. Unlike molarity, it uses solvent mass and is unaffected by thermal volume changes.
Titration: A quantitative method that determines an analyte's amount by reacting it with a measured solution. Titration infers an unknown concentration from reaction stoichiometry and measured volumes.
Normality: The number of chemical equivalents of solute per liter of solution. Its reaction-dependent equivalent count differs from ordinary amount concentration.
Osmosis: The net movement of solvent across a selectively permeable membrane toward higher solute concentration. Differences in dissolved concentration can move water across biological membranes.

Linked from 53 pages