The rate of any particular reaction depends upon the following factors:
1. Nature of the reactants:
Let us consider the following two reactions:
2 NO (g) + O2 (g) ————-> 2 NO2 (g) …………….. Fast
2 CO (g) + O2 (g) ————-> 2 CO2 (g) …………….. Slow
These reactions appear to be similar but the first is fast while second is slow. This is due to the difference in the amounts of energies which are required for breaking up of different bonds and different amounts of energies are released in the formation of different bonds.
2. Concentration of the reactants:
Greater the concentration of the reactants, faster is the reaction. Conversely, as the concentrations of the reactants decrease, the rate of reaction also decreases.
3. Temperature:
The rate of reaction increases with increase of temperature. In most of the cases, the rate of reaction becomes nearly double for 10K rise of temperature. In some cases, reactions do not take place at room temperature but take place at higher temperature.
4. Presence of catalyst:
A catalyst generally increases the speed of a reaction without itself being consumed in the reaction. In case of reverse reactions, a catalyst helps to attain the equilibrium quickly without disturbing the state of equilibrium.
5. Surface area of the reactants:
For a reaction involving a solid reactant or catalyst, the smaller is the practical size, greater is the surface area, and the faster is the reaction.
6. Presence of light:
Some reactions do not take place in the dark but can take place in the presence of light like photosynthesis or photochemical reactions.
