Question

By increasing temperature of reaction from \[{\text{300K}}\] to \[{\text{310K}}\],the kinetic energy (or average kinetic energy) of reactant molecules increases only by 3% but for most of the reaction the rate have almost doubled by increase in temperature by 10. Explain why?

Answer 1

Hint: The rates of almost all reactions increase with the increase in temperature. In most of the cases the rate of the reaction becomes double for every \[{\text{1}}{{\text{0}}^{\text{0}}}\] rise in temperature. This is expressed in terms of temperature coefficient.


Complete step by step answer:
Most of the facts of chemical kinetics have been derived from the collision theory. According to this theory, a chemical reaction occurs only as a result of collisions between the reacting molecules. The collisions that bring about chemical reactions to happen are called effective collisions. The number of effective collisions is linked with the kinetic energy of the reacting molecules. To increase the rate of reaction, we have to increase the kinetic energy and the best way to do so is to increase the temperature.
Most of the reactions become double by a \[{\text{1}}{{\text{0}}^{\text{0}}}\] increase in temperature. This is expressed in terms of temperature coefficient which is the ratio of rate constants of the reaction at two temperatures differing by \[{\text{1}}{{\text{0}}^{\text{0}}}\]. The two temperatures generally selected are \[{\text{298}}\;{\text{K and 308 K}}\]. Thus,
\[{\text{Temperature coefficient = }}\dfrac{{{\text{Rate}}\;{\text{constant at 308 K}}}}{{{\text{Rate}}\;{\text{constant at 298 K}}}}\]
Rise in temperature increases the kinetic energy as kinetic energy is directly proportional to temperature. When we plot a graph between energy and process of reaction after increasing the temperature, we can see that the number of molecules possessing higher kinetic energy, which is greater than the minimum required energy will be double and therefore the rate of reaction increases.
Therefore, increase in the rate of reactions is due to an increase in the number of effective collisions, as increase in temperature increases the kinetic energy of the molecules.

Additional Information:
The rate of encounters between the reacting species depends upon some more factors like the concentration of the reactants and the surface area of the reacting substances. Increased concentration of reactant molecules increases the chances of effective collisions.

Note: Increase in temperature increases the rate of reaction. This is because of the fact that as a reaction is carried out by the effective collisions of reacting molecules, the increase in temperature increases their kinetic energy and thereby increases the number of effective collisions.