Increased temperature is expected to affect a chemical reaction’s reaction rate. The rate constant of reaction ratio at two different 10˚c called Temperature co-efficient of the reaction.
Suppose two different temperatures select are 25˚c and 35˚c.
Most of the reaction value of temperature co-efficient is nearer to two, and in some cases, nearer three. The collision theory explains the slightly increasing temperature and speeding up a reaction to a large extent.
According to this theory, chemical reactions start due to the collision between the reactant molecules, and most collisions between the molecules are ineffective.
The essential factor of collision theory is that only those collision results come out in a chemical reaction in which the colliding molecules are together with specific minimum energy called Threshold energy.
Maxwell’s distribution of molecular energies explains the temperature dependence of reaction rates. The general shift in the distribution of energies is shown in the figure; as the temperature increase from T1 to T2, the energy distribution change.
As shown in the figure, more molecules are on the high side of kinetic energy. The shaded area efcd represented is the number of molecules whose energies are equal to or greater than the threshold energy E at temperatures T1 and T2 by the shaded area abcd.
The shaded area abcd is nearly twice that of the shaded area efcd. It means that the number of molecules having energy equal to or grater than the threshold energy becomes close to double even with a slight temperature increase from T1 to T2.
Figure 1. Energy distribution in molecules at two different temperature
What is Activation energy?
Activation energy is excess energy in which the reactant molecules have less than the threshold energy.
Activation energy = Threshold energy – Energy actually possessed by molecules
An energy barrier is placed between reactant and product, shown in figure 2. The barrier determines the magnitude of threshold energy, which reactant molecules must acquire before they can yield products.
Figure2. Energy barrier in chemical reaction
EFFECT OF CATALYST ON REACTION RATE
What is a catalyst?
A catalyst is a substance that increases the rate of a chemical reaction without taking part in the chemical reaction end; catalyst composition remains the same.
It is simply the equilibrium approach that speeds up both the forward and backward reactions.
Effects of catalyst on rate of reaction
