What is chamical equilibrium ? Write the characteristics of the chemical equilibrium.

Options

A. Permanency of equilibrium
B. Approachability from either side
C. Incompleteness of reaction
D. All of these

Answer

### Step-by-Step Text Solution

**Step 1: Definition of Chemical Equilibrium**
Chemical equilibrium is the state of a chemical reaction where the rate of the forward reaction equals the rate of the backward reaction. This means that the concentrations of reactants and products remain constant over time, even though the reactions continue to occur.

**Step 2: Explanation of Forward and Backward Reactions**
In a chemical reaction represented as:
\[ aA + bB \rightleftharpoons cC + dD \]
where \( A \) and \( B \) are reactants and \( C \) and \( D \) are products, the forward reaction is the conversion of reactants into products, while the backward reaction is the conversion of products back into reactants. At equilibrium, the rate of formation of products \( C \) and \( D \) is equal to the rate of formation of reactants \( A \) and \( B \).

**Step 3: Law of Mass Action**
According to the law of mass action, the equilibrium constant \( K \) can be expressed in terms of the concentrations of the reactants and products at equilibrium:
\[ K = \frac{[C]^c [D]^d}{[A]^a [B]^b} \]
where \([C]\), \([D]\), \([A]\), and \([B]\) are the molar concentrations of the respective species at equilibrium, and \( a, b, c, d \) are their stoichiometric coefficients.

**Step 4: Le Chatelier's Principle**
When a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the equilibrium will shift in a direction that counteracts the change. This is known as Le Chatelier's Principle. For example, if the concentration of reactants is increased, the equilibrium will shift to the right to produce more products.

**Step 5: Dynamic Nature of Equilibrium**
Chemical equilibrium is dynamic, meaning that even though the concentrations of reactants and products remain constant, the reactions continue to occur in both directions. The forward and backward reactions are still happening, but at equal rates.

**Step 6: Attainability from Both Directions**
Equilibrium can be attained from either the forward direction (starting with reactants) or the backward direction (starting with products). This shows that the system can reach equilibrium regardless of the initial concentrations of reactants or products.

### Characteristics of Chemical Equilibrium
1. **Rate Equality**: The rate of the forward reaction equals the rate of the backward reaction.
2. **Constant Concentrations**: The concentrations of reactants and products remain constant over time.
3. **Dynamic Process**: The reactions continue to occur, but the rates are equal.
4. **Law of Mass Action**: The equilibrium constant can be calculated using the concentrations of reactants and products.
5. **Response to Changes**: The system adjusts to changes in concentration, temperature, or pressure according to Le Chatelier's Principle.
6. **Attainable from Both Sides**: Equilibrium can be reached from either the reactants or products.