IIT JEE , AIEEE Forum - Articles Category , Community shelf - KINETICS----an introduction to basics

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Chemical kinetics is the branch of chemistry which deals with rate and mechanism of chemical reaction.
The speed with which the reactants are converted into products are called rate of reaction.
the rate of reaction is also defined as change in concentration of any one of the product or reactants per unit time.
The significance in of negative sign in case of expressing rate of reaction in terms of reactant is important.We know that rate is always positive, as also obtained from the rate of formation of products. Therefore, minus sign is put before dA/dT so that rate is positive i,e, in A-----B ,rate of reaction is given by -dA/dT.
the reaction rate cannot be determined by dividing total change in concentration by the time taken as in the case of mechanical speed.
as the reaction progresses, the rate of reaction decreases as the concentration of reactant decreases.
The rate of a reaction that does not involve a gas does not depend upon pressure.
The rate constant of a reactiom increases with increase of temperature but not affected by concentration or catalyst.
The rate of rxn does not depend upon the reactant present in large excess.
The rate of reaction must be expressed with reference to particular moment of time.
The average rate can be calculated by dividing the concentration difference by the time interval.
The rate of reaction is not constant but it decreases with time reaching a value zero when the reaction is complete.
The rate of change of concentration of any one of the reactants or products at a given time is called instantaneous rate.
The time taken by a certain reaction to proceed to a certain definite stage (98%) is called LIFE TIME OF THE REACTION.
The time ,the reaction takes to proceed midway is called HALFLIFE period.
Law of mass action was given by 2 norwegian scientist GULDBERG and WAAGE.
RATE LAW are the mathematical expression which expresses the observed rate of reaction in terms of concentration of reacting species.
RATE CONSTANT of a reaction is the rate of reaction when the molar concentration of each of the reactant is unity.
ORDER OF REACTION is the sum of exponents of the concentration terms in the rate law.
order of the reaction can be zero ,integer or fractional.
the units of rate constant depend on the order of the reaction.
the specific rate constant of a first order reaction depends only upon the temperature.
A reaction is of first order when the rate is linearly related to concentration of the reactant.
For the first order reaction plot of log{A} vs time is linear with negative slope.
Certain bimolecular reaction which follow the kinetics of first order are called pseudounimolecular ractions.
Hydrolysisi of ester in presence of alkaline medium is a second order reaction.
the units of rate constant is [LITRE]n-1 [mole]1-n sec-1 where n is order of the reaction.
molecularity of the reaction is defined as number of reacting molecules which collide simultaneously to bring about a chemical reaction.
molecularity of a reaction cannot be zero.it has whole number values only.

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