Order of Reaction

#. First order reaction: A reaction is said to be first order if its reaction rate is determined by the variation of one concentration term only.

• The integrated rate equation expresses the concentration of reactants as a function of time.

• The integrated rate equation for a first order reaction is given as

#. Second order reaction: The reaction in which sum of powers of concentration terms in rate law equation is two.

#. Zero order reaction: Those reactions in which rate of reaction does not change with concentration of the reactants.

Rate law for such a reaction is expressed as. Rate = k [A]°[B]°

#. Half life period: It is the time required for the initial concentration of the reactant to be reduced to half its value.

#. The temperature coefficient of a reaction is the ratio of the rate constants of the reaction at two temperatures differing from one another by 10°C. The two temperatures usually taken are 35 °C and 25 °C.

• The variation of rate constants with temperature can be represented by the Arrhenius equation,
K=Ae^-Ea/Rt
 where A is a constant known as frequency factor, and Ea is-called the energy of activation.
From the above equation, the rate constants at two different temperatures are related as