Chemistry FACTORS AFFECTING THE RATE OF REACTIONS

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FACTORS AFFECTING THE RATE OF REACTIONS

Factors Affecting the Rate of Reaction :

The most important factors which influence the rate of reaction are concentration, temperature and catalyst.

The most important factors which influence the rate of reaction are concentration, temperature and catalyst.

Concentration :

In the case of most of the reactions, the rate of a reaction increase with the concentration of their reactants. The reason can be explained on the basis of collision theory. With the increases in the concentration of the reactants, the number of reactant molecules per unit volume increases thereby increasing the number of effective collisions. With the increase in the collision frequency, the rate of reaction increases.

In the case of most of the reactions, the rate of a reaction increase with the concentration of their reactants. The reason can be explained on the basis of collision theory. With the increases in the concentration of the reactants, the number of reactant molecules per unit volume increases thereby increasing the number of effective collisions. With the increase in the collision frequency, the rate of reaction increases.

Temperature :

In general, the rate of reaction increases with the increase in temperature. With the increase in temperature, the kinetic energy of the reactant molecules increases. Therefore, more number of molecules acquires threshold energy and this result in more effective collisions.

In general, the rate of reaction increases with the increase in temperature. With the increase in temperature, the kinetic energy of the reactant molecules increases. Therefore, more number of molecules acquires threshold energy and this result in more effective collisions.

Catalyst :

A catalyst is a substance which alters the rate of a reaction without undergoing any net change in its composition. A catalyst alters the
rate of reaction by making the reaction to take place in an alternative pathway. Generally, most of the catalysts reduce the activation energy of the reaction. Since the alternative reaction path is associated with lower activation energy, more number of effective collision take place and hence greater is the rate of reaction.

There are few reactions in which catalysts decrease the rate of reaction. These are called negative catalysts.

Glycerin, urea, acetanilide, pyrophosphate decrease the rate decomposition of `H_2O_2` and hence stabilizers for `H_2O_2`.

Though it is possible to increase the rate of reaction by increasing the temperature, the use of catalyst has a lot of significance in the
industrial processes. This is because carrying out a process at a lower temperature in the presence of catalyst reduces the cost of
production to a large extent. Increasing the temperature is not feasible in the case of some reactions.

A catalyst is a substance which alters the rate of a reaction without undergoing any net change in its composition. A catalyst alters the
rate of reaction by making the reaction to take place in an alternative pathway. Generally, most of the catalysts reduce the activation energy of the reaction. Since the alternative reaction path is associated with lower activation energy, more number of effective collision take place and hence greater is the rate of reaction.

There are few reactions in which catalysts decrease the rate of reaction. These are called negative catalysts.

Glycerin, urea, acetanilide, pyrophosphate decrease the rate decomposition of `H_2O_2` and hence stabilizers for `H_2O_2`.

Though it is possible to increase the rate of reaction by increasing the temperature, the use of catalyst has a lot of significance in the
industrial processes. This is because carrying out a process at a lower temperature in the presence of catalyst reduces the cost of
production to a large extent. Increasing the temperature is not feasible in the case of some reactions.

Surface Area of the Reactants :

For a reaction involving a solid reactant or catalyst, the smaller is the particle size, i.e., greater is the surface area, the faster is the reaction.

For a reaction involving a solid reactant or catalyst, the smaller is the particle size, i.e., greater is the surface area, the faster is the reaction.

Presence of light :

`H_2+Cl_2-> 2HCl`

Some reactions do not take place in the dark but take place in the presence of light as given above. Such reactions are called Photochemical reactions.

`H_2+Cl_2-> 2HCl`

Some reactions do not take place in the dark but take place in the presence of light as given above. Such reactions are called Photochemical reactions.

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