15
Chemical Kinetics
THE LAW OF MASS ACTION
The rate of a chemical reaction depends on several important factors but,
except for the case where a molecule is unstable and spontaneously decomposes, there is a very basic requirement that two interacting molecules must
first collide with each other before any kind of reaction can occur. A collision
between two potentially reacting molecules does not necessarily mean that a
reaction will occur, but at least there's the possibility. The greater the frequency
of collision, the faster the reaction is likely to be. The one factor that determines the frequency of collision is concentration: the higher the concentrations
of the reactants, the greater the number of molecules per unit volume, and the
greater the collision frequency. This basic principle was first put forth quantitatively in 1863 by Guldberg and Waage in their statement of the law of mass
action, which asserts that, for a general reaction of the type
aA + bE + cC + • • • ^mM + nN + • • •
(15-1)
the rate (V) of the reaction at a given temperature will be
V = A:[A]
a [B]
6 [C]
c • • •
(15-2)
Chemical Kinetics
THE LAW OF MASS ACTION
The rate of a chemical reaction depends on several important factors but,
except for the case where a molecule is unstable and spontaneously decomposes, there is a very basic requirement that two interacting molecules must
first collide with each other before any kind of reaction can occur. A collision
between two potentially reacting molecules does not necessarily mean that a
reaction will occur, but at least there's the possibility. The greater the frequency
of collision, the faster the reaction is likely to be. The one factor that determines the frequency of collision is concentration: the higher the concentrations
of the reactants, the greater the number of molecules per unit volume, and the
greater the collision frequency. This basic principle was first put forth quantitatively in 1863 by Guldberg and Waage in their statement of the law of mass
action, which asserts that, for a general reaction of the type
aA + bE + cC + • • • ^mM + nN + • • •
(15-1)
the rate (V) of the reaction at a given temperature will be
V = A:[A]
a [B]
6 [C]
c • • •
(15-2)