Chemical equilibrium & Dynamic equilibrium

Chemical Equilibrium:

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Chemical equilibrium is a state in a chemical reaction where the concentrations of reactants and products remain constant over time. In a reversible reaction, the forward and reverse reactions occur simultaneously at the same rate. When the rates of the forward and reverse reactions become equal, the system is in a state of dynamic equilibrium.

Characteristics of Chemical Equilibrium:

1. Constant Concentrations:

• The concentrations of reactants and products no longer change, but the reactions continue to occur.
• The rate of the forward reaction equals the rate of the reverse reaction.

1. Equilibrium Constant (K):

• The ratio of the concentrations of products to reactants at equilibrium is constant and is known as the equilibrium constant (K).
• For a general reaction (aA + bB \rightleftharpoons cC + dD), the equilibrium constant expression is given by (K = \frac{[C]^c [D]^d}{[A]^a [B]^b}).

1. Direction of Reaction:

• A system at equilibrium can shift in either the forward or reverse direction based on changes in temperature, pressure, or concentration.

1. No Macroscopic Changes:

• There are no observable changes in color, temperature, pressure, or any other macroscopic properties of the system.

1. Reversible Reactions:

• Chemical equilibrium is more commonly associated with reversible reactions where products can revert to reactants.

Dynamic Equilibrium:

Dynamic equilibrium is a specific type of equilibrium that occurs in a closed system where opposing processes, such as evaporation and condensation, occur at the same rate. In the context of chemical reactions, dynamic equilibrium refers to a situation where the rates of the forward and reverse reactions are equal, leading to a stable concentration of reactants and products.

Key Features of Dynamic Equilibrium:

1. Continuous Motion:

• While concentrations remain constant, individual molecules are still in motion, participating in both forward and reverse reactions.

1. No Net Change:

• There is no net change in the concentration of reactants or products, but the reactions are ongoing.

1. Equilibrium State:

• The system is in a state where opposing processes balance each other, resulting in a stable condition.

1. Reversibility:

• Dynamic equilibrium is associated with reversible processes where products can convert back to reactants and vice versa.

1. Closed System:

• Dynamic equilibrium occurs in a closed system where the exchange of matter with the surroundings is restricted.

Examples:

• Chemical Equilibrium: In the reaction (N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)), when ammonia is synthesized, a state of chemical equilibrium is reached when the concentrations of (N_2), (H_2), and (NH_3) remain constant.
• Dynamic Equilibrium: In a closed container of water, the process of evaporation and condensation of water molecules establishes dynamic equilibrium. The rate of water molecules leaving the liquid surface (evaporation) equals the rate at which water vapor condenses back into the liquid state.