In chemistry, what varies with the number of molecules present in a sample of a particular substance?

concentration

Explanation:

Concentration refers to the amount of a substance present in a sample. The more molecules of a substance present in a sample, the greater its concentration. The less molecules of a substance in a sample, the lesser the concentration. We are often concerned about analytically determining the concentration of a substance using diverse analytical methods in chemistry.

adding or remove a gaseous reactant or product changes the concentrations. if the concentration of reactant or product is increased, the system will shift away from the side in which concentration was increased (i.e. if the concentration of reactants is increased, the system will shift toward the products. if more products are added, the system will shift to form more reactants). conversely, if the concentration of reactant or product is decreased, the system will shift toward the side in which concentration was decreased (i.e. if reactants are removed, the system will shift to form more reactants. if the concentration of products is decreased, the equilibrium will shift toward the products).

explanation: