Question

The equilibrium constant for a reaction, $A + B \rightleftharpoons C + D$ is $1 \times {10^{ - 2}}$ at $298K$ and is 2 at $273K$ . The chemical resulting in the formation of C and D is:
A.Exothermic
B.Endothermic
C.Unpredictable
D.There is no relationship between $\Delta H$ and K

Answer 1

Hint: In an exothermic reaction, heat is released. In an endothermic reaction, heat is consumed. Hence, when the temperature increases in an exothermic reaction, equilibrium shifts towards left, and when the temperature decreases, equilibrium shifts towards right.

Complete step by step answer:
Le- Chatelier’s principle which is also known as “the equilibrium law” states that when a system is subjected to some physical changes like temperature, concentration, or pressure, then the equilibrium constant changes accordingly.
 But the changes depend upon the types of reactions such as exothermic or endothermic reactions.
The effect of change in temperature in a reaction can be predicted by, whether the system is releasing or absorbing heat.
The given reaction is reversible. Here, when the temperature decreases from $298K$ to $273K$ , the equilibrium constant increases from $1 \times {10^{ - 2}}$ to 2. Hence, an increase in temperature equilibrium is shifting towards the left. This happens in an exothermic reaction where \[\Delta H\] is negative and heat is released.
As we have decided on the relationship between $\Delta H$ and K, option D is incorrect.
The reaction is quite predictable and according to Le Chatelier’s principle, in an endothermic reaction, with increases in temperature, equilibrium shifts towards the product that is right where \[\Delta H\] is positive and heat is absorbed which is opposite to the condition that is given in the question. Hence options B and C are incorrect.

So, the correct answer is Option A.

Note: Le- Chatelier’s principle explains the behavior of a system when there is a change made externally via temperature, pressure, or volume. Hence changes in the behavior of the system occur to oppose the external changes. The time taken by the system to adjust depends upon the strength of external changes. This law can be used to describe the mechanical system as well via the mechanism.