Chemical Equilibrium

Study Notes

Chemical Equilibrium

Chemical equilibrium is the state where the forward and reverse reaction rates are equal, resulting in no net change in the concentrations of reactants and products.
At equilibrium, the rates of the forward and reverse reactions are equal.
Equilibrium is dynamic, meaning that the reactions continue to occur, but the concentrations of reactants and products remain constant.
Equilibrium position refers to the relative concentrations of products and reactants at equilibrium.

Le Chatelier's Principle

Le Chatelier's Principle states that if a stress is applied to a system in equilibrium, the system will shift in a direction that relieves the stress.
Common stresses include changes in concentration, pressure, temperature, and the addition of a catalyst.
Increasing the concentration of a reactant shifts the equilibrium to the right (product-favored).
Increasing the concentration of a product shifts the equilibrium to the left (reactant-favored).
Changing pressure affects systems with gaseous reactants and products. Increasing pressure shifts the equilibrium towards the side with fewer moles of gas.
Increasing temperature favors the endothermic reaction.
Adding a catalyst does not shift the equilibrium, just speeds up the rate at which it is reached.

Equilibrium Constants

Equilibrium constant (K) is a numerical value that relates the concentrations of products and reactants at equilibrium.
Equilibrium constant values vary for different reactions and have different units depending on the balanced equation.
A large K value indicates that the reaction strongly favors the products, meaning there are more products than reactants at equilibrium.
A small K value indicates that the reaction strongly favors the reactants, meaning there are more reactants than products at equilibrium.

Factors Affecting Equilibrium

Concentration: Adding more reactants or products will shift the equilibrium to counter that change.
Pressure: Pressure changes are important for systems with gases. Changes in pressure cause shifts in the equilibrium with gases in the reaction to favor the side with fewer gas molecules.
Temperature: Changes in temperature affect the equilibrium by changing the value of the equilibrium constant. The shift depends on whether the reaction is endothermic or exothermic.
Catalyst: Catalysts increase the rate of both forward and reverse reactions equally, so they do not affect the equilibrium position.

Calculating Equilibrium Constants

The equilibrium constant (K) is calculated using the concentrations of the products and reactants at equilibrium.
For a general reversible reaction: aA + bB ⇌ cC + dD, the equilibrium constant expression is: K = [C]^c[D]^d / [A]^a[B]^b
Brackets represent molar concentrations.
The coefficients in the balanced equation become the exponents in the equilibrium constant expression.

Redox Reactions

Redox reactions involve the transfer of electrons between reactants.
Oxidation is the loss of electrons, and reduction is the gain of electrons.
Oxidizing agents are substances that cause oxidation and are reduced during the reaction.
Reducing agents are substances that cause reduction and are oxidized during the reaction.
Redox reactions are crucial in many chemical processes such as combustion, corrosion, and electrochemistry.
Identifying the oxidation states and balancing the reaction equations are necessary for analyzing redox reactions.
Common oxidation states need to be memorized to quickly determine and balance the chemical equations involved in a redox reaction.

Description

Test your understanding of chemical equilibrium and Le Chatelier's Principle. This quiz covers the fundamental concepts such as dynamic equilibrium, the effects of stress on equilibrium systems, and the principles guiding shifts in reaction rates. Perfect for students studying chemistry at various levels.