1) Chemical kinetic 
A reaction rate is the speed at which reactants are converted into products in a chemical reaction. The reaction rate is given as the instantaneous rate of change for any reactant or product, and is usually written as a derivative (e. g. d[A]/dt) with units of concentration per unit time (e. g. mol L-1 s-1).
The reaction rate (rate of reaction) or speed of reaction for a reactant or product in a particular reaction is intuitively defined as how fast or slow a reaction takes place. For example, the oxidative rusting of iron under Earth`s atmosphere is a slow reaction that can take many years, but the combustion of cellulose in a fire is a reaction tha....
the speed at which a chemical reaction proceeds. It is often expressed in terms of either the concentration (amount per unit volume) of a product ... [9 related articles]
quantity giving the number of interactions of a given type occurring by unit of time