If the following equilibrium is subjected to pressure increase, what will happen?
[tex]2 NO _2(g)[/tex] brown [tex]\rightleftharpoons N _2 O _4(g)[/tex] colorless + energy
A. more reactants will be created
B. Keq will increase
C. it will become more brown
D. it will become more colorless
Answer (1)
The equilibrium shifts to relieve the stress of increased pressure.
The reaction shifts towards the side with fewer moles of gas.
The forward reaction produces fewer moles of gas, so it's favored.
The mixture becomes more colorless as more N 2 O 4 is formed. i tw i ll b eco m e m oreco l or l ess
Explanation
Understanding the Problem The problem describes a chemical equilibrium: 2 N O 2 ( g ) brown ⇌ N 2 O 4 ( g ) colorless + energy. We need to determine what happens when the pressure is increased.
Applying Le Chatelier's Principle Le Chatelier's principle states that if a change of condition is applied to a system in equilibrium, the system will shift in a direction that relieves the stress. In this case, the stress is an increase in pressure.
Determining the Shift in Equilibrium An increase in pressure will cause the equilibrium to shift in the direction that reduces the number of moles of gas. In the given reaction, the forward reaction ( 2 N O 2 ( g ) → N 2 O 4 ( g ) ) reduces the number of moles of gas from 2 to 1.
Concluding the Effect on Color Therefore, the equilibrium will shift to the right, favoring the formation of N 2 O 4 . Since N 2 O 4 is colorless, the mixture will become more colorless.
Examples
Le Chatelier's principle is used in many industrial processes to optimize the yield of desired products. For example, in the Haber-Bosch process for the synthesis of ammonia ( N 2 + 3 H 2 ⇌ 2 N H 3 ), high pressure is used to shift the equilibrium towards the formation of ammonia, as the forward reaction reduces the number of moles of gas. This principle is also crucial in environmental science to understand how changes in temperature or pressure can affect chemical reactions in the atmosphere or aquatic systems.
