118.
How does temperature affect the rate of a reaction? Is there a corresponding equal decrease in number of collisions among molecules of a gaseous reaction? How is this effect explained by the concept of activation energy?
Temperature usually has a major effect on the rate of a chemical reaction. Molecules at a higher temperature have more thermal energy. Although collision frequency is greater at higher temperatures. When the temperature of reaction mixture is increased, the kinetic energy of molecules increases which results in increase in velocity of molecules which in turn, results in increase in number effective, collisions; For every 10°C rise in temperature the rate of the reaction becomes double-fold to five-fold. There is no corresponding increase in the number of collision among the gaseous molecules because for 10°C rise in temperature the increase in number of collisions is only 2 to 3 percent. This many fold increase in the rate of the reaction is explained by the concept of activation energy. Only those collisions are effective and result in the formation of product where the molecules possess a certain minimum amount of energy over and above their average energy which is called the activation energy. For every 10°C rise in temperature, the number of activated molecules increase by 200 to 500% and therefore the reaction rate becomes double to five fold.
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