of reaction rate is atm s - . . . Stoichiometry and rate of a reaction: In reaction B , the stoichiometry of both reactant and product are same, and hence the rate of disappearance of reactant (A) and the rate of appearance of product (B) are same.
Now, let us consider a different reaction 2B In this case, for every mole of A, that disappears two moles of B appear, i.e., the rate of formation of B is twice as fast as the rate of disappearance of A. Therefore, the rate of the reaction can be expressed as below Rate = + d[B] dt -d[A] dt In other words, Rate = -d[A] dt d[B] dt = For a general reaction, the rate of the reaction is equal to the rate of consumption of a reactant (or formation of a product) divided by its coefficient in the balanced equation x y l m A + B C + D Rate - d[A] dt - d[B] dt d[C] dt d[D] dt x y l m . . .
. . Concentraon(M) Time (mins) * Schematic representation- Not to scale * -A -B Fig . change in concentration of A and B for the reaction A B XII U7 kinetics - Jerald XII U7 kinetics - Jerald - - - - .
. Average and instantaneous rate: Let us understand the average rate and instantaneous rate by considering the isomerisation of cyclopropane. K cyclopropane propene The kinetics of the above reaction is followed by measuring the concentration of cyclopropane at regular intervals and the observations are shown below. (Table .
) Table . Concentration of cyclopropane at various times during its isomerisation at 780K Time ( min) [cyclopropane] ( mol L - ) . . .
Rate of the reaction= – ∆ [cyclopropane] ∆ t The rate over the entire min = - - ) molL ( - ) min - ( . = . . molL min -