CHEM122 Chemical Equilibrium

Chemical Equilibria

Dynamic processes where reactions occur in both forward and reverse directions.

Equilibrium Constant (K)

The ratio of the forward rate constant to the reverse rate constant at equilibrium.

Dynamic Equilibrium

A state where the concentrations of reactants and products remain constant over time.

Le Chatelier's Principle

When a system at equilibrium is subjected to a stress, the system shifts to counteract the stress.

Reaction Quotient (Q)

A ratio that indicates how far a reaction has progressed toward equilibrium.

Forward Reaction

The reaction where reactants are converted into products.

Reverse Reaction

The reaction where products are converted back into reactants.

Stoichiometry

The calculation of reactants and products in chemical reactions.

Exothermic Reaction

A reaction that releases heat energy, resulting in a negative ΔH.

Endothermic Reaction

A reaction that absorbs heat energy, resulting in a positive ΔH.

Competing Reactions

Reactions that occur simultaneously and can affect each other's rates.

Rate of Reaction

The speed at which reactants are converted to products.

Kc

Equilibrium constant expressed in terms of concentrations.

Kp

Equilibrium constant expressed in terms of partial pressures.

Δn

Change in the number of moles of gas; used to convert Kc to Kp.

Catalyst

A substance that increases the rate of a reaction without being consumed.

Pressure in Equilibrium

Changes in pressure can shift the position of the equilibrium in gaseous reactions.

High Temperature Condition

Necessary for the industrial synthesis of ammonia.

Ice Table

A table used to track the initial concentrations, changes, and equilibrium concentrations.

Equilibrium Position

The concentrations of reactants and products when a system has reached equilibrium.

Stress on Equilibrium

Any change in concentration, temperature, or pressure that disturbs equilibrium.

Reciprocal Equilibrium Constant

K' = 1/K when a reaction is reversed.

Equilibrium Shift to Right

Occurs when products are favored, increasing product concentration.

Equilibrium Shift to Left

Occurs when reactants are favored, increasing reactant concentration.

Thermodynamic Quantities

Values that describe the energy changes in reactions and the position of equilibrium.

Synthesis of Ammonia

An important industrial process involving the reaction of nitrogen and hydrogen.

Chemical Reaction Types

Includes precipitation, acid-base, and oxidation-reduction reactions.

Equilibrium and Rate Comparison

At equilibrium, rates of forward and reverse reactions are equal.

Volume Change Effect

Changing the volume of a reaction container shifts equilibrium to relieve pressure.

Addition of Inert Gas

Increases total pressure but does not affect the equilibrium position.

Temperature Change Effect

Alters the value of the equilibrium constant and the position of equilibrium.

Quadratic Equation in Chemistry

Used to calculate unknown concentrations at equilibrium.

Equilibrium Composition

The concentrations of reactants and products in a system at equilibrium.

Equilibrium Dynamic Process

Reactions proceeding in both directions continuously while concentrations remain constant.

Chemical Systems

Systems in which chemical reactions are occurring, often at equilibrium.

Equilibrium Constant Calculation

Determining the ratio of product and reactant concentrations at equilibrium.

Forward Rate Law

Rate of forward reaction expressed as kf[reactants].

Reverse Rate Law

Rate of reverse reaction expressed as kr[products].

Reversible Reaction

A reaction that can proceed in both the forward and reverse directions.

Equilibrium Constant Relationships

K changes with temperature; constant for a given reaction at a fixed temperature.

Kp Calculation

Derived from the expression involving partial pressures of gases at equilibrium.

Effect of Concentration Change

A change in the concentration of reactants or products shifts the equilibrium.

Stress from Temperature Change

Increasing temperature favors endothermic reactions; decreasing it favors exothermic reactions.

High Yield Reaction Condition

Requires specific conditions, like temperature and pressure, for optimal product formation.

Checking Equilibrium Constants

Comparing calculated values within a set range to determine accuracy.

Equilibrium Dynamics Importance

Understanding equilibrium allows prediction of reaction shifts with changes in conditions.

Stoichiometric Calculations

Use of balanced chemical equations to relate quantities of reactants and products.

Industrial Catalyst Importance

Catalysts are crucial for increasing the efficiency of industrial reactions.

Equilibrium and Gibbs Free Energy

The relationship between equilibrium constants and the spontaneity of reactions.

Equilibrium Systems Understanding

A clear comprehension of how equilibrium works is essential for predicting changes.

What is chemical equilibrium?

A state where the rates of forward and reverse reactions are equal, leading to stable concentrations of reactants and products.

How can Le Chatelier’s Principle be stated?

If a system at equilibrium is subjected to a change in concentration, temperature, or pressure, the system adjusts to counteract that change.

What does K represent in equilibrium calculations?

The equilibrium constant, representing the ratio of concentrations of products to reactants at equilibrium.

What does Kc indicate?

The equilibrium constant expressed in terms of molar concentrations.

What does Kp indicate?

The equilibrium constant expressed in terms of partial pressures of gases.

How is the equilibrium constant calculated?

By taking the ratio of the concentrations of the products raised to their stoichiometric coefficients to that of the reactants.

What happens to equilibrium when pressure is increased?

The system shifts towards the side with fewer moles of gas to alleviate the pressure.

How does temperature affect equilibrium position?

Increasing temperature favors the endothermic reaction; decreasing it favors the exothermic reaction.

What does a shift to the right in equilibrium indicate?

Products are favored, leading to increased concentration of products.

What does a shift to the left in equilibrium indicate?

Reactants are favored, leading to increased concentration of reactants.

How do catalysts affect chemical equilibria?

Catalysts speed up the rate of both forward and reverse reactions equally without changing the equilibrium position.

What is an ICE table?

A tool used to track Initial concentrations, Changes, and Equilibrium concentrations of reactants and products.

What does Δn represent in Kc to Kp conversions?

The change in the number of moles of gas, used to relate Kc and Kp.

How can the reaction quotient (Q) be defined?

The ratio of the concentrations or pressures of products to reactants at any point in the reaction, not just at equilibrium.

What happens when concentration of reactants is increased?

The equilibrium shifts to the right, favoring the formation of products.

What is the role of chemical equilibrium graphs?

Graphs illustrate the changes in concentrations of reactants and products over time, showing how they approach equilibrium.

What is a characteristic of a reversible reaction?

It can proceed in both the forward and reverse directions.

What is the main takeaway from Le Chatelier's Principle regarding stress?

Systems will shift to counteract any applied stress and restore equilibrium.

How can equilibrium constants shift with temperature changes?

Equilibrium constants vary with temperature; they are constant at a fixed temperature for a given reaction.

What is the significance of stoichiometry in equilibrium calculations?

Stoichiometry allows for the calculation of the amounts of reactants and products at equilibrium based on balanced equations.

What effect does adding an inert gas have on equilibrium?

It increases total pressure but does not change the equilibrium position.

In graphical terms, what signifies a system at equilibrium?

The concentrations of reactants and products remain constant when plotted over time.

How can temperature influence Kc values?

Temperature changes can alter the value of the equilibrium constant, Kc, reflecting the direction of the heat exchange.

What does it mean if K > 1?

Products are favored at equilibrium, indicating they are more concentrated than reactants.

What does it mean if K < 1?

Reactants are favored at equilibrium, indicating they are more concentrated than products.

What is a dynamic equilibrium?

A state where the forward and reverse reaction rates are equal while concentrations remain constant.

Why is understanding equilibrium dynamics important in chemistry?

It allows for predicting reaction shifts and optimizing conditions for desired product formation.

What is the effect of volume decrease on gaseous equilibrium?

A decrease in volume shifts the equilibrium towards the side with fewer moles of gas.

What does equilibrium constant relationship Kp to Kc indicate?

Kp can be calculated from Kc using the ideal gas law and Δn values.

What is the primary use of quadratic equations in equilibrium problems?

Quadratic equations solve for unknown concentrations at equilibrium when dealing with complex reactions.

What do chemical equilibrium rate graphs illustrate?

They show the changes in the rates of forward and reverse reactions over time until equilibrium is reached.

How do the slopes of the lines in an equilibrium rate graph relate to reaction rates?

The slopes indicate the speed of the reactions; a steeper slope denotes a faster reaction rate.

What does it mean when the lines in an equilibrium rate graph converge?

It indicates that the rates of the forward and reverse reactions have become equal, signaling that equilibrium has been achieved.

Chemical equilibrium occurs when the rates of the forward and reverse reactions are __________.

equal.

The equilibrium constant (K) is expressed as the ratio of __________ to __________.

products; reactants.

In an ICE table, the 'I' stands for __________, the 'C' for changes, and the 'E' for __________.

Initial concentrations; Equilibrium concentrations.

A __________ reaction is one that can proceed in both the forward and reverse directions.

reversible.

When increasing the temperature of an exothermic reaction, the equilibrium will shift to the __________.

left.

If the concentration of a product is increased, the equilibrium will shift to the __________.

left.

When the volume of a reaction vessel decreases, the equilibrium shifts towards the side with fewer __________.

moles of gas.

The __________ law relates the equilibrium constant to the concentrations of the reactants and products at equilibrium.

mass action.

The reaction quotient (Q) can be used to determine how far a reaction is from __________.

equilibrium.

Graphs of chemical equilibria illustrate the __________ of the reactants and products over time.

concentrations.

For equilibrium constants, if K > 1, it indicates that the __________ are favored at equilibrium.

products.

At __________ equilibrium, changes in concentration or temperature will shift the system to maintain a new equilibrium state.

dynamic.

The slope of a line in a rate graph represents the __________ of a reaction.

rate.

A shift to the __________ in equilibrium indicates that reactant concentrations are increasing.

left.

When a catalyst is added to a reaction, it lowers the __________ energy barrier for both reactions, not changing the position of equilibrium.

activation.

Changes in __________ can affect the equilibrium constant value, K.

temperature.

The __________ of a reaction measures the speed at which reactants are converted into products.

rate.