The rate of reaction depends upon the following factors.
(i) Nature of the reactions:
(i) `2NO_((g))+P_(2(g))to 2NO_(3(g))to "Fast"`
`2CO_((g))+ O_(2(g))to 2CO_(2(g))to "Slow"`
These reactions appear to be similar but the first is fast while second is slow. This is due to the difference in the amouts of energies which are required for breaking up of different bonds and different amounts of energies are released in the formation of different bonds.
(b) ` 2Al +6HCl to 2AlCl_(3) + 3H_(2)uarr`
`Zn +2HCl to NzCl_(2) +H_(2) uarr`
Al and Zn react with dilute hydrochloric acid, `H_(2)` gas is liberated and water soluble salts of the metals are formed. however, the reaction of aluminium metal takes place faster as compared to zinc metla. The nature of metal is responsible fro this difference. Al is more reactive thn Zn. Therefore, the rate of reaction of Al with hydrochloric acid is higher than the of zinc. Nature of reactivity of reactants influences the rate of a chemical reaction.
(ii) 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 decrease. Dilute HCl reacts slowly with `CaCO_(3)` and thereby, `CaCO_(3)` disappears slowly and `CO_(2)` also liberates slowly on the other hand the reaction with concentrated HCl takes plce rapidly and `CaCO_(3)` disappears fast. Concentrated acid reacts faster than dilute acid, which means that rate of reaction is proporational to the concentration of reactants.
Temperaturre:
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.
(iv) Presence of catalyst:
A catalyst generally increases the speed of a reaction without itself being consumed in the reactin. In case of reverse reaction, a catalyst helps to attain the equilibrium quickly without disturibing the state of equilibrium.
(v) Size of the particles of reactants :
For a reaction involving a solid reactant or catalyst, smaller the particle size, greater is the surface area, and faster is the reaction.
(vi) Presence of light :
Some reactions do not take place in the dark but can take plce in the presence of light like photosynthesis or photochemical reactions.
