CHEM 12!! - Equilibrium

What does Le Chatelier's Principle state?

When a system at equilibrium is subjected to a stress, it will attempt to minimize that stress by shifting to establish a new equilibrium.

What are the three types of stresses that can affect a chemical system at equilibrium?

Changing the concentration of a reactant or product, changing the temperature of the system, and changing the pressure of the system.

What happens when you add more N2 to an ammonia equilibrium system?

The system shifts right to consume N2.

What is the effect of adding more NH3 to an ammonia equilibrium system?

The system shifts left to consume NH3.

What occurs when NH3 is removed from the ammonia equilibrium system?

The system shifts right to produce more NH3.

How does increasing the temperature affect an exothermic reaction at equilibrium?

The system shifts left to remove heat.

What happens when the temperature is decreased in an exothermic reaction at equilibrium?

The system shifts right to add heat.

What is the relationship between pressure and the number of gas molecules in a system at equilibrium?

Increasing pressure shifts the equilibrium toward the side with fewer gas molecules.

What occurs when pressure is decreased in a system at equilibrium?

The system shifts left toward the side with more gas molecules.

Why is the addition of a catalyst not considered a stress in a chemical system?

A catalyst speeds up both forward and reverse reactions equally but does not change the position of the equilibrium.

What is homeostasis in the context of biological systems?

The process by which biological systems adjust to maintain equilibrium despite external stresses.

What is the significance of the ammonia (NH3) equilibrium in food production?

Ammonia is crucial for fertilizers, and shifting the equilibrium to produce more NH3 is beneficial for increasing food production.

What is the effect of adding heat to an endothermic reaction at equilibrium?

The system shifts right to consume the added heat.

What does it mean for a reaction to be exothermic?

It releases heat during the reaction, which can be treated as a product.

How can you visualize the effects of stress on equilibrium?

Graphical representations can show how the system shifts in response to changes in concentration, temperature, or pressure.

What is a common method to remove a compound from a system at equilibrium?

Physical removal methods, such as using a syringe, can be employed without affecting other compounds.

What is the role of temperature in chemical equilibria?

Temperature changes can shift the position of equilibrium depending on whether the reaction is exothermic or endothermic.

What happens to the equilibrium when the pressure is increased in a system with 4 gas molecules on one side and 2 on the other?

The system shifts right toward the side with 2 gas molecules.

What is the effect of decreasing the pressure in a system with unequal gas molecules?

The system shifts left toward the side with more gas molecules.

How does the concept of stress apply to chemical equilibria?

Stress causes the system to react by shifting to counteract the change and restore equilibrium.

What is the opposite action of the system when a stress is applied?

The system will do the opposite of what the stress entails to minimize its effects.

What is an example of a biological equilibrium that can be stressed?

The balance of pH levels in the human body can be affected by diet and exercise.

How does Le Chatelier's Principle relate to homeostasis?

Both concepts involve systems adjusting to maintain balance despite external changes.

What is the importance of understanding Le Chatelier's Principle in chemical reactions?

It helps predict how changes will affect the position of equilibrium in chemical reactions.

What type of arrow is used to indicate reversible reactions?

A double arrow is used to indicate reversible reactions.

What does dynamic equilibrium mean in a chemical reaction?

Dynamic equilibrium means that both forward and reverse reactions are occurring at the same rate.

What are the observable properties of a system at equilibrium?

The macroscopic properties (pressure, colour, concentration, pH) are constant.

What type of system must be present for equilibrium to occur?

The system must be closed, such as a sealed container.

Can equilibrium be established from either direction?

Yes, equilibrium can be reached whether starting with only reactants, only products, or a mixture of both.

What does it mean when concentrations of reactants and products are constant at equilibrium?

It means that the concentrations are not changing, but they do not have to be equal.

What is the equilibrium constant (Keq)?

Keq is a numerical value that describes the relative position of the equilibrium.

Which substances are included in the equilibrium constant expression?

Only gases and aqueous solutions are included; solids and liquids are not.

What does the reaction quotient (Q) indicate?

Q indicates whether a system is at equilibrium by comparing it to Keq.

What does it mean if Q = K?

The system is at equilibrium.

What does it mean if Q < K?

The system is not at equilibrium yet; it needs to shift to the right to reach equilibrium.

What does it mean if Q > K?

The system is not at equilibrium yet; it needs to shift to the left to reach equilibrium.

In the example with SO2Cl2, what is the equilibrium reaction?

SO2Cl2 ⇌ SO2 + Cl2

What is the value of K for the reaction involving SO2Cl2 at 100 ºC?

K = 0.078 at 100 ºC.

How do you determine the equilibrium constant from a reaction?

By calculating the concentrations of the products and reactants at equilibrium.

What is the significance of a closed system in equilibrium?

It prevents the exchange of matter with the surroundings, allowing for a stable equilibrium.

What happens to the macroscopic properties if any property is changing?

If any macroscopic property is changing, then the system is not at equilibrium.

What is an example of a steady state system that is not at equilibrium?

A sink that is collecting and draining water at the same rate.

How can you visualize dynamic equilibrium?

By imagining running on a treadmill where you and the treadmill move at the same speed in opposite directions.

What is the role of temperature in equilibrium reactions?

Temperature can affect the position of equilibrium and the value of the equilibrium constant.

What is the relationship between the concentrations of reactants and products at equilibrium?

The concentrations remain constant but are not necessarily equal.

What does a shift to the right in a reaction indicate?

It indicates that the formation of products is favored.

What does a shift to the left in a reaction indicate?

It indicates that the formation of reactants is favored.

Type 1 Equilibrium Calculation

This type involves finding an unknown concentration when the system is already at equilibrium.

Equilibrium Constant (K)

A numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium at a given temperature.

Example of Type 1 Calculation

If K is 49.70 at 458 ºC and the concentrations of two species are both 1.07 M, find the concentration of HI at equilibrium.

Type 2 Equilibrium Calculation

This type involves given initial conditions and allowing the system to reach equilibrium using an ICE table and the 'perfect squares' procedure.

ICE Table

A table used to organize the Initial concentrations, Change in concentrations, and Equilibrium concentrations of reactants and products.

Example of Type 2 Calculation

At 900 ºC, K = 4.200. Find the concentrations of all species at equilibrium if 4.000 moles of each reactant are placed into a 1.000-L flask.

Type 3 Equilibrium Calculation

This type involves given initial conditions and allows the system to reach equilibrium using an ICE table and a shortcut to avoid solving a polynomial equation.

Example of Type 3 Calculation

If K is 6.40 x 10^-7 at 2000 ºC, find the concentration of all species at equilibrium if 0.25 moles of CO2 is placed into a 1-L flask.

Type 4 Equilibrium Calculation

This type involves given initial conditions and uses an ICE table to find concentrations using the quadratic formula when the shortcut from Type 3 does not apply.

Example of Type 4 Calculation

At 150 ºC, K = 4.50. Find the concentrations of all species at equilibrium if 0.5 moles of N2O4 is placed into a 1.000-L flask.

Perfect Squares Procedure

A method used in Type 2 calculations to find concentrations at equilibrium when the reaction can be simplified to a perfect square.

Quadratic Formula in Equilibrium

A mathematical formula used to find the roots of a quadratic equation, applied in Type 4 calculations to determine concentrations at equilibrium.

Equilibrium Concentration

The concentration of a species in a chemical reaction at equilibrium, determined by the equilibrium constant and initial conditions.

Initial Conditions

The concentrations of reactants and products before the system reaches equilibrium.

Moles to Concentration

To find concentration, divide the number of moles of a substance by the volume of the solution in liters.

Temperature's Role in K

The value of the equilibrium constant (K) is temperature-dependent and varies with changes in temperature.

Chemical Equilibrium

A state in a reversible reaction where the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products.

What is Ksp?

Ksp, or solubility product constant, is an equilibrium constant that applies to the solubility of a sparingly soluble ionic compound.

What happens when a solute is dissolved in a solvent?

When a solute is dissolved in a solvent, it can produce different types of solutions, with varying degrees of solubility.

What is dynamic equilibrium in a solubility context?

Dynamic equilibrium occurs when the rate of dissolution of a solid solute equals the rate of precipitation of its ions, resulting in constant ion concentrations.

Why are solids not included in Ksp equations?

Solids are not included in Ksp equations because the equilibrium expression only accounts for the concentrations of ions in solution.

What is the Ksp equation for silver sulfide (Ag2S)?

The Ksp equation for silver sulfide dissolving in water is Ksp = [Ag+]^2[S2-].

How to calculate ion concentrations from Ksp?

To find the concentrations of ions from a given Ksp value, set up the equilibrium expression and solve for the ion concentrations.

What is the Ksp of AgBr if its solubility is 7.1 x 10^-7 moles/L?

The Ksp of AgBr can be calculated using the formula Ksp = [Ag+][Br-], where both concentrations equal the solubility value.

What is the Ksp of silver chromate (Ag2CrO4) if its solubility is 6.7 x 10^-5 moles/L?

The Ksp of silver chromate can be calculated using the formula Ksp = 4[Ag+]^2[CrO4^2-], where the concentrations are derived from the solubility.

What is the significance of mixing solutions in Ksp calculations?

Mixing solutions can lead to precipitation if the product of the ion concentrations exceeds the Ksp value of the resulting compound.

Will a precipitate form when 150 mL of 0.10 M Pb(NO3)2 is combined with 100 mL of 0.20 M NaCl?

To determine if a precipitate forms, calculate the concentrations of Pb^2+ and Cl^- after mixing and compare the ion product to the Ksp of PbCl2.

What is the role of water as a solvent in Ksp calculations?

Water acts as a solvent that dissolves ionic compounds, allowing for the establishment of equilibrium and the calculation of Ksp.

What is solubility?

Solubility is the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature.

What does it mean for a solution to be saturated?

A saturated solution is one in which no more solute can dissolve at a given temperature, and the solution is in equilibrium with the undissolved solute.

What is an equilibrium arrow?

An equilibrium arrow indicates that the reaction can proceed in both the forward and reverse directions, typical for reactions involving solubility.

What is the relationship between solubility and Ksp?

Higher solubility generally leads to a higher Ksp value, as more ions are present in solution at equilibrium.

What is the significance of ion concentrations in Ksp?

Ion concentrations are crucial for calculating Ksp and determining whether a precipitate will form when solutions are mixed.

What is a precipitate?

A precipitate is an insoluble solid that forms when the product of the concentrations of ions in solution exceeds the Ksp.

What is the formula for calculating Ksp from solubility?

Ksp can be calculated using the formula Ksp = [Cation]^m[Anion]^n, where m and n are the stoichiometric coefficients from the balanced dissolution equation.

What is the importance of temperature in Ksp calculations?

Temperature affects solubility and, consequently, the Ksp value; Ksp values are typically reported at a specific temperature.

What is the common ion effect?

The common ion effect refers to the decrease in solubility of an ionic compound when a common ion is added to the solution.

How does the common ion effect apply to ionic salts?

The common ion effect applies to ionic salts by reducing their solubility in a solution that already contains one of the ions present in the salt.

What is an example of the common ion effect?

An example is the solubility of silver chloride (AgCl) in distilled water compared to its solubility in seawater, where the presence of chloride ions from seawater decreases the solubility of AgCl.

What mass of AgCl can be dissolved in 1 L of distilled water?

The specific mass of AgCl that can be dissolved in 1 L of distilled water is not provided in the notes, but it is generally higher than in seawater due to the absence of common ions.

What mass of AgCl can be dissolved in 1 L of seawater?

The mass of AgCl that can be dissolved in 1 L of seawater is lower than in distilled water due to the presence of common chloride ions that reduce its solubility.