Equilibrium Concepts in Chemistry

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Questions and Answers

What happens to the equilibrium when the concentration of a reactant is decreased?

It shifts towards the favored side of the products.

It remains unchanged.

It shifts to the left, favoring the reactants. (correct)

It shifts to the right, favoring the products.

When increasing the pressure in a gaseous reaction, how does the equilibrium shift?

Towards the side with the same number of moles of gas.

It does not shift at all.

Towards the side with fewer moles of gas. (correct)

Towards the side with more moles of gas.

In an endothermic reaction, what happens when the temperature is increased?

The equilibrium shifts to the right, favoring the products. (correct)

The equilibrium shifts to the left, favoring the reactants.

The equilibrium remains constant.

The reaction rate decreases.

Which of the following factors does NOT affect the position of equilibrium?

Presence of catalysts Signup and view all the answers

What characterizes homogeneous equilibrium?

Reactants and products are in the same phase. Signup and view all the answers

What is the key characteristic of a system at equilibrium?

The rates of the forward and reverse reactions are equal. Signup and view all the answers

Which statement accurately describes dynamic equilibrium?

Both forward and reverse reactions occur simultaneously at equal rates. Signup and view all the answers

How does increasing the concentration of a reactant affect the equilibrium position?

Equilibrium shifts to the right, favoring products. Signup and view all the answers

What does the equilibrium constant (Kc) represent?

The ratio of product concentrations to reactant concentrations at equilibrium. Signup and view all the answers

Which of the following is a type of chemical equilibrium?

The synthesis of ammonia from nitrogen and hydrogen. Signup and view all the answers

What happens to the value of Kc if the temperature of an equilibrium system is increased?

Kc is temperature dependent and can change. Signup and view all the answers

According to Le Chatelier's Principle, if pressure increases in a gaseous equilibrium system, the equilibrium will shift:

To the side with fewer moles of gas. Signup and view all the answers

What defines physical equilibrium?

It pertains to physical changes such as phase transitions. Signup and view all the answers

Study Notes

Equilibrium

Equilibrium is a state where the rates of the forward and reverse reactions are equal, and the net change in the concentration of reactants and products is zero.
A system at equilibrium is dynamic, meaning that the forward and reverse reactions are still occurring, but at equal rates.
Equilibrium is characterized by constant macroscopic properties such as concentration, pressure, and color.

Types of Equilibrium

Physical Equilibrium: Involves physical changes like phase transitions (solid-liquid, liquid-gas).
- Example: Water in equilibrium with its vapor in a closed container.
Chemical Equilibrium: Involves chemical reactions.
- Example: The reaction between nitrogen and hydrogen to form ammonia.

Dynamic Equilibrium

In a reversible reaction, the forward reaction and reverse reaction proceed simultaneously.
At equilibrium, the rates of the forward and reverse reactions are equal.
The concentrations of reactants and products remain constant.

Characteristics of Equilibrium

The rates of the forward and reverse reactions are equal.
The net change in the concentrations of reactants and products is zero.
The macroscopic properties of the system remain constant.
The system is dynamic.

Law of Chemical Equilibrium

The law describes the relationship between the concentrations of reactants and products at equilibrium for a reversible reaction.
It is expressed using the equilibrium constant (Kc).

Equilibrium Constant (Kc)

Kc is a numerical value that describes the ratio of product concentrations to reactant concentrations at equilibrium.
For the general reversible reaction: aA + bB ⇌ cC + dD
The equilibrium constant expression is: Kc = [C]^c [D]^d / [A]^a [B]^b
Where [ ] represents the molar concentrations.
Kc is temperature dependent. A change in temperature results in a change in Kc.

Importance of Equilibrium Constant

Predicts the extent of reaction completion.
Indicates the relative amount of reactants and products at equilibrium.
Helps in determining the direction of a reaction.

Effect of Change in Conditions on Equilibrium (Le Chatelier's Principle)

If a change is imposed on a system at equilibrium, the position of equilibrium shifts to counteract the change.
Factors affecting equilibrium: concentration, pressure, and temperature.

Concentration Change

Increasing the concentration of a reactant, the equilibrium shifts to the right, favoring the products.
Decreasing the concentration of a reactant, the equilibrium shifts to the left, favoring the reactants.

Pressure Change

Increasing the pressure of a gaseous system, the equilibrium shifts towards the side with fewer moles of gas.
Decreasing the pressure, the equilibrium shifts towards the side with more moles of gas.

Temperature Change

Increasing the temperature of an exothermic reaction, the equilibrium shifts to the left, favoring the reactants.
Increasing the temperature of an endothermic reaction, the equilibrium shifts to the right, favoring the products.

Examples of Equilibrium Reactions

Ionization of weak acids and bases.
Dissolution of sparingly soluble salts.
Formation of complexes.
Haber-Bosch process for ammonia synthesis.

Equilibrium and Chemical Kinetics

Equilibrium is a state where the forward and reverse reactions occur at equal rates.
Chemical kinetics describes the rates of these reactions.
Understanding both kinetics and equilibrium is crucial to predicting and controlling chemical reactions.

Factors Determining Equilibrium Position

Nature of reactants and products
Temperature
Pressure
Presence of catalysts
Concentration of reactants and products

Calculating Equilibrium Concentrations

Techniques using ICE tables to find equilibrium concentrations.
Substitution into equilibrium constant expressions for calculations.

Homogeneous and Heterogeneous Equilibrium

Homogeneous equilibrium involves the reactants and products in the same phase.
Heterogeneous equilibrium involves substances in different phases.

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Description

This quiz explores the principles of equilibrium, including its definition and types such as physical and chemical equilibrium. It also covers the dynamic nature of equilibrium in reversible reactions, emphasizing the significance of equal reaction rates.