Consider a reversible reaction –
A +B C + D
According to law of mass action ,
Rate of reaction ∝ [A][B]
R= K [A][B]
K= Velocity constt.
if [A] = [B] = 1
“If molar concentration of reactants are unity then velocity constt. is equal to the rate of reaction.”
Factors affecting Rate constant or velocity constant-
Rate of reaction increases in presence of catalyst thus velocity constant increases in presence of catalyst.
Rate of reaction increases with increase in temperature. Therefore, value of velocity constt. increases.