Question

Which factor, when decreased will cause a reaction to proceed more quickly?
A) Exothermic
B) Particle size
C) Endothermic
D) Catalyst
E) Concentration

Answer 1

An exothermic reaction is defined as the reaction in which the energy is released in the form of heat or light. In an exothermic reaction the energy is transferred to the surroundings rather than taken from surroundings. The change in enthalpy in the exothermic reaction is always negative. So the amount of energy which is required during an exothermic reaction is less than the amount of energy released in reaction.

Complete answer:
Endothermic reaction is defined as the reaction in which the energy is absorbed from the surroundings so that the products can be formed. The enthalpy change in the endothermic reaction is always positive. During this reaction the entropy of the surrounding decreases. Catalyst is defined as the substance which is used in reaction so that the reaction can be altered by changing the path the reaction. The catalyst does not initiate the reaction. It cannot be consumed in the reaction.

So in this quest van’t hoff equation will be used/ the van’t hoff equation is :
$\dfrac{\partial [\ln K]}{\partial T}=\dfrac{\Delta {{H}^{o}}}{R{{T}^{2}}}$
Now if the reaction is endothermic then the $\Delta {H^o} > 0$ so then the $\dfrac{\partial [\ln K]}{\partial T}=+ve$

So then the ${{K}_{p}}$will increase, that is the equilibrium constant will increase with temperature. But if the reaction is exothermic then with decrease in ${{K}_{p}}$the temperature will increase. So for the reaction to be proceeded the exothermic nature of the reaction should be decreased. These are the factors which we can determine and predict by Le- Chatelier principle.

So the correct option is option ‘C’.

Note: Exothermic reaction is processed during combustion. In this reaction the fuel undergoes reduction when it gets exposed to the oxidising agent. Exothermic reaction is also processed in respiration also. The energy which is produced in the reaction tells us that it is an exothermic reaction. The other examples of exothermic reaction are neutralization reaction, nuclear fission of uranium -235.