Question

According to Le chatelier’s principle:
A.An increase in pressure always causes a change in position of equilibrium for any reaction.
B.The yield of \[N{H_3}\] decrease from its constitution at lower temperature
C.An increase in temperature always causes a decrease in the value of \[Kc\] for an exothermic reaction.
D.The \[Kc\] is decreased for the reaction \[A + B \to C\], if the concentration of A is increased.

Answer 1

Hint: Equilibrium represents the state of process in which the properties like temperature, pressure, concentration of the system do not show any change with the passage of time. The example of equilibrium is in economics when supply and demand are equal.

Complete step by step answer:
First we will discuss about the Le chatelier’s principle
Le chatelier’s principle: - It is a principle of chemistry used to predict the effect of change in conditions like concentration, temperature, volume and pressure on chemical equilibrium. The system changes into new equilibrium and this change partly counteracts the applied change. The principle was given by French chemist Henry Louis Le chatelier and also known as “ Chatelier’s principle” or “The Equilibrium law”.
Now we will discuss about the formula used in Chatelier’s principle
\[A{\text{ }} + B{\text{ }} = {\text{ }} - C + {\text{ }}D\]
 (A and B = reactant or C OR D is product)
\[Kc{\text{ }} = {\text{ }}\dfrac{{\left( {{\text{ }}C} \right){\text{ }} + {\text{ }}\left( D \right){\text{ }}}}{{\left( A \right){\text{ }} + {\text{ }}\left( B \right)\;}}\]
In this reaction \[Kc\] is equilibrium constant.
According to formula, some factors affect the chemical reaction like concentration, temperature, volume and pressure.
Concentration: The concentration of reactant decreases if the reaction in equilibrium and A and B react to form C and D. So equilibrium shifts in forward direction. The effect of change in concentration is condensation reaction.
Temperature: - The change in temperature alters the state of equilibrium for only those reactions in which either heat is evolved (exothermic reaction) and heat absorb (endothermic reaction.
\[{N_2}{\text{ }} + {\text{ }}3{H_2}{\text{ }} = {\text{ }}2N{H_3}.\;\;\;\]
(If the forward reaction is exothermic, the backward reaction will be endothermic)
If the temperature is increased, heat is supplied to the system then according to Le chatelier’s principle, the equilibrium will shift to the side that heat absorbs i.e backward direction. Similarly decrease in temperature shifts the equilibrium in forward direction.
Volume and Pressure: - if the volume of a gaseous reaction is decreased, the pressure exerted by the molecules will increase.
Hence, option (A) is correct.


Note:
The principle states that formation of \[N{H_3}\] is an endothermic reaction favoured by increase in temperature. The system counteracts change by producing more heat. In case of increasing (A), the equilibrium position will move so that concentration will decrease again and \[Kc\] will increase.