Reaction rate

The reaction rate of a chemical reaction, that is, the speed of production of products or reactants, may generally be expressed as rate = k [a]^x where [a] is the molar concentration of reactant (there may be several), x is the order for that reactant, and k is a constant. Order establishes the mathematical relation of concentration to rate; eg. for an order of 2, if the concentration doubles, the rate quadruples.

Rate is often expressed in moles per liter-second. There are many factors that affect on the rate of reaction:

Reaction rate for the chemical reaction a -> products

can be expressed:

-r = k [a]

Rate r is negative, because reaction consumes A. Usually reactions are equilibrium reactions. For example: a + b <=> x + y Reaction rate equation for above reaction can be expressed:

-r = k1 [a][b] - k2 [x][y]

, where k1 is rate constant for the reaction which consumes a and b. "k2" is rate constant for the backwards reaction, which consumes x and y and which products are a and b.

There is correlation between k1 and k2.

K = k1/k2

K is equilirium constant for the reaction.

Reaction rate constant k has temperature dependedancy, which is:

k = A*exp(Ea/RT)

where A is the frequency factor and Ea is the reaction's activation energy. Formula shown above is known as Arrhenius equation.