Define rate constant (k).

Explanation

Rate of reactions : The rate of reaction at any instant of time is the rate of change of concentration of any one of the reactants or products at that particular intstant of time. . For example, for the hypothetical reaction,
`2A+B rarr 3C`
Rate=`-1/2(d[A])/(dt)=-(d[B])/(dt)=1/3(d[C])/(dt)`
Rate constant or specific .rate constant : For the hypothetical reaction
`aA + bB rarr` Products
Rate = `k[A]^(alpha)[B]^(beta)`
In this expression [A] and [B] are molar concentrations of A and B respectively k is rate constant. When,
[A]=[B]=1
Rate=k
Thus, rate constant of a reaction is defined as the rate of reaction when molar concentration of all the reactants is unity. It is also called specific reaction rate.