Test: Dynamic Nature of Equilibrium - NEET MCQ

Understanding Dynamic Equilibrium

• Dynamic equilibrium refers to a state of balance achieved by two processes occurring at the same rate. 
• At dynamic equilibrium, the concentrations of the reactants and products do not change because the rates of the forward and backward reactions are the same. This is a state of balance, but not necessarily a state of equality.
• The concentrations of reactants and products at dynamic equilibrium are not necessarily equal. They are constant, but not necessarily the same.

Conclusion
So, the correct answer is d. remain constant. At dynamic equilibrium, the concentration of the reactants and the products remain constant. 

• Equilibrium in Closed System: Equilibrium can be attained in a closed system because the energy exchange can occur until the system's properties reach a balance. For instance, chemical equilibrium or thermal equilibrium can be achieved in a closed system.
• Not in Open or Isolated Systems: In open systems, matter and energy can be exchanged with the surroundings, disturbing the balance. Isolated systems, on the other hand, and cannot exchange energy or matter with the surroundings, so they cannot reach equilibrium with their surroundings.

 

• Water is a dynamic equilibrium with ice at the freezing point of water that is zero degrees centigrade, 273 Kelvin and 32-degree Fahrenheit.
• Because at zero degrees centigrade the phase transition occurs.

Explanation of Equilibrium Reactions in Large Scale Production of Ammonia and Sulfuric Acid
Equilibrium reactions play a significant role in the large scale production of various substances. Here, we will be discussing two such substances, ammonia and sulfuric acid.
1. Ammonia Production

• The production of ammonia (NH₃) on a large scale is carried out using the Haber-Bosch process. In this process, nitrogen (N₂) and hydrogen (H₂) react to produce ammonia.
• The reaction is reversible and reaches a state of equilibrium. The reaction can be represented as: N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
• The rate at which the forward reaction (production of ammonia) occurs equals the rate at which the reverse reaction (decomposition of ammonia) occurs when the system is in equilibrium.
• The conditions of temperature, pressure, and the use of a catalyst are carefully controlled to favor the formation of ammonia.

2. Sulfuric Acid Production

• Sulfuric acid (H₂SO₄) is produced on a large scale using the Contact process. This process involves several steps, and a state of equilibrium is reached in one of these steps.
• In this process, sulfur dioxide (SO₂) is first produced by burning sulfur in air. The sulfur dioxide is then oxidized to sulfur trioxide (SO₃) in the presence of a catalyst (V₂O₅). This reaction is reversible and reaches a state of equilibrium: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g).
• Just like in the production of ammonia, the conditions of temperature, pressure, and the use of a catalyst are carefully controlled to favor the formation of sulfur trioxide, which is then used to produce sulfuric acid.
  Hence, both ammonia and sulfuric acid production involve equilibrium reactions on a large scale.

Silver chloride forms a soluble complex with aqueous ammonia.
AgCl + 2NH₃→ [Ag(NH₃)₂]Cl

The statement "All the physical processes stop at equilibrium" represents a common misunderstanding of what equilibrium means. In fact, at equilibrium, the forward and reverse reactions do not stop. They continue to occur, but at the same rate, making it look like the system is static. This is often referred to as dynamic equilibrium.

In a chemical reaction a state comes when both the forward and reverse reactions occur at the same rate and this state is known as equilibrium. At the beginning of the reaction, the rate of the Forward reaction is higher than the rate of backward reaction.

The Haber Process combines nitrogen from the air with hydrogen derived mainly from natural gas (methane) into ammonia. The reaction is reversible and the production of ammonia is exothermic.
At each pass of the gases through the reactor, only about 15% of the nitrogen and hydrogen converts to ammonia. By continual recycling of the unreacted nitrogen and hydrogen, the overall conversion is about 98%.

Reversible Reaction

In a reversible reaction, reactants can be converted into products, and products can also react to form reactants. The chemical equation for a reversible reaction can be written in both forward and reverse directions. For example: A+B⇌C+D

Law of mass action states that the rate of reaction is proportional to the product of molar concentration of reactant with each concentration term raised to power its stoichiometric coefficient.