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Chemical equilibrium is characterized by the complete cessation of all molecular motion and reaction processes.
Answer: False
Chemical equilibrium is a dynamic state characterized by equal forward and reverse reaction rates, not a cessation of molecular motion or reaction processes.
Claude Louis Berthollet first proposed the concept of chemical equilibrium in 1803, based on his observations of reversible reactions.
Answer: True
The concept of chemical equilibrium was first developed by Claude Louis Berthollet in 1803, stemming from his studies of reversible chemical reactions.
The equilibrium position describes the specific rate constants governing the forward and reverse reactions.
Answer: False
The equilibrium position refers to the relative amounts of reactants and products at equilibrium, not the specific rate constants.
What defines the state of chemical equilibrium in a reaction?
Answer: The forward reaction rate equals the reverse reaction rate, resulting in constant concentrations.
Chemical equilibrium is defined by the state where the rate of the forward reaction equals the rate of the reverse reaction, leading to constant macroscopic properties, including concentrations.
Who is credited with developing the concept of chemical equilibrium based on the reversibility of reactions?
Answer: Claude Louis Berthollet
Claude Louis Berthollet is credited with developing the concept of chemical equilibrium in 1803, based on his observations of reversible reactions.
What does the 'equilibrium position' indicate about a reaction?
Answer: The relative amounts of reactants and products at equilibrium.
The equilibrium position describes the relative concentrations or partial pressures of reactants and products present once equilibrium has been established.
The Law of Mass Action, proposed by Guldberg and Waage, accurately describes the rate of all chemical reactions, regardless of their complexity.
Answer: False
The Law of Mass Action, while foundational, accurately describes the rate of elementary reactions; it does not universally describe the rate of all chemical reactions, particularly complex multi-step processes.
The equilibrium constant (K) is defined as the ratio of the rate constant for the reverse reaction to the rate constant for the forward reaction.
Answer: False
The equilibrium constant (K) is defined as the ratio of the rate constant for the forward reaction (k+) to the rate constant for the reverse reaction (k-), i.e., K = k+/k-.
The reaction quotient (Qr) is used to determine the direction a reaction will proceed only when the system is already at equilibrium.
Answer: False
The reaction quotient (Qr) is used to determine the direction a reaction will proceed at any point, not solely when the system is already at equilibrium.
If Qr < Keq, the reaction will proceed in the reverse direction to reach equilibrium.
Answer: False
If Qr < Keq, the reaction will proceed in the forward direction towards products to reach equilibrium.
According to the Law of Mass Action, the rate of a chemical reaction is proportional to:
Answer: The product of the concentrations of reactants, each raised to its stoichiometric coefficient.
The Law of Mass Action states that the rate of a chemical reaction is proportional to the product of the concentrations of the reactants, each raised to the power of its stoichiometric coefficient.
If the reaction quotient Qr is greater than the equilibrium constant Keq, the reaction will proceed:
Answer: In the reverse direction towards reactants.
If Qr > Keq, the ratio of products to reactants is too high, indicating that the reaction must proceed in the reverse direction to reach equilibrium.
What is the relationship between the equilibrium constant (K) and the rate constants (k+ for forward, k- for reverse)?
Answer: K = k+ / k-
The equilibrium constant (K) is fundamentally the ratio of the rate constant for the forward reaction (k+) to the rate constant for the reverse reaction (k-).
At equilibrium, the Gibbs free energy of a system reaches its maximum value.
Answer: False
At equilibrium, the Gibbs free energy of a system reaches its minimum value under constant temperature and pressure.
The van 't Hoff equation relates the change in equilibrium constant to changes in pressure and volume.
Answer: False
The van 't Hoff equation relates the change in equilibrium constant to temperature and the standard molar enthalpy change (ΔH°) of the reaction.
For an endothermic reaction, the equilibrium constant increases as temperature increases.
Answer: True
For endothermic reactions (ΔH° > 0), the equilibrium constant (K) increases with increasing temperature, as predicted by the van 't Hoff equation.
Minimizing the Gibbs free energy of a system requires solving equations based on the conservation of mass and the definition of chemical potential.
Answer: True
The minimization of Gibbs free energy at equilibrium is achieved by solving a system of equations that incorporates mass conservation constraints and the relationships between chemical potentials.
The relationship ΔrG° = -RTlnKeq shows that a positive standard Gibbs free energy change corresponds to a large equilibrium constant.
Answer: False
The relationship ΔrG° = -RTlnKeq indicates that a negative standard Gibbs free energy change corresponds to a large equilibrium constant.
The entropy of mixing is irrelevant to the determination of chemical equilibrium as it only affects the physical state, not the chemical composition.
Answer: False
The entropy of mixing contributes to the overall Gibbs free energy and is therefore relevant to the determination of chemical equilibrium.
The condition (dG/dξ)T,p = 0 signifies that the system has reached a state of minimum Gibbs free energy at constant temperature and pressure.
Answer: True
The condition (dG/dξ)T,p = 0 signifies that the system has reached a state of minimum Gibbs free energy at constant temperature and pressure, which is the criterion for equilibrium.
Which thermodynamic quantity reaches a minimum at equilibrium under constant temperature and pressure?
Answer: Gibbs Free Energy (G)
Under conditions of constant temperature and pressure, a system reaches equilibrium when its Gibbs Free Energy (G) is minimized.
The van 't Hoff equation relates the change in equilibrium constant (K) to temperature (T) and which other key reaction property?
Answer: Standard Enthalpy change (ΔH°)
The van 't Hoff equation relates the temperature dependence of the equilibrium constant (K) to the standard molar enthalpy change (ΔH°) of the reaction.
The equation ΔrG° = -RTlnKeq relates the standard Gibbs free energy change to:
Answer: The equilibrium constant.
The equation ΔrG° = -RTlnKeq establishes a direct relationship between the standard Gibbs free energy change of a reaction and its equilibrium constant.
How does temperature affect the equilibrium constant for an exothermic reaction?
Answer: K decreases as temperature increases.
For an exothermic reaction (ΔH° < 0), an increase in temperature shifts the equilibrium to the left, decreasing the equilibrium constant (K).
What does the condition αμA + βμB = σμS + τμT represent at equilibrium?
Answer: The equality of chemical potentials of reactants and products.
At equilibrium, the sum of the chemical potentials of reactants, weighted by their stoichiometric coefficients, equals the sum of the chemical potentials of products, weighted by their stoichiometric coefficients.
A catalyst shifts the equilibrium position towards the products by increasing the rate of the forward reaction more than the reverse reaction.
Answer: False
A catalyst increases the rates of both forward and reverse reactions equally, thereby accelerating the attainment of equilibrium but not shifting its position.
Le Chatelier's principle predicts that if a system at equilibrium is disturbed, it will shift in a direction that enhances the disturbance.
Answer: False
Le Chatelier's principle states that a system at equilibrium, when disturbed, will shift in a direction that counteracts the applied change.
What is the primary effect of a catalyst on a system at equilibrium?
Answer: It increases the rate at which equilibrium is reached.
A catalyst accelerates both the forward and reverse reaction rates equally, thus reducing the time required to reach equilibrium without altering the equilibrium position or constant.
According to Le Chatelier's principle, if the concentration of a product is increased in a system at equilibrium, the equilibrium will shift:
Answer: Towards the reactants to consume the excess product.
According to Le Chatelier's principle, an increase in product concentration will cause the equilibrium to shift towards the reactants to counteract the change.
Which principle helps predict how an equilibrium system will respond to changes in temperature, pressure, or concentration?
Answer: Le Chatelier's Principle
Le Chatelier's Principle provides a framework for predicting the direction in which an equilibrium system will shift in response to external changes in conditions such as temperature, pressure, or concentration.
Pure solids and liquids are included in the equilibrium constant expression with their respective concentrations.
Answer: False
Pure solids and liquids are excluded from equilibrium constant expressions because their activities are considered constant and equal to one.
Homogeneous equilibrium occurs when reactants and products exist in different physical phases.
Answer: False
Homogeneous equilibrium occurs when all reactants and products are in the same physical phase, whereas heterogeneous equilibrium involves multiple phases.
Mass-balance equations ensure that the total concentration of each element remains constant throughout a reaction.
Answer: True
Mass-balance equations are statements that ensure the total concentration of each element or species remains constant throughout the reaction, adhering to the law of conservation of mass.
Activity coefficients are used to adjust concentrations in equilibrium expressions to account for non-ideal behavior in solutions.
Answer: True
Activity coefficients are employed in equilibrium expressions to correct concentrations for non-ideal behavior in solutions, thereby ensuring accurate thermodynamic calculations.
For gas-phase reactions, fugacity is used instead of partial pressure to account for non-ideal behavior.
Answer: True
In gas-phase reactions, fugacity serves as the thermodynamic variable that accounts for non-ideal behavior, analogous to how activity coefficients adjust concentrations in solutions.
In solutions, higher ionic strengths generally lead to activity coefficients that are closer to unity.
Answer: False
In solutions, higher ionic strengths generally lead to activity coefficients that deviate further from unity, reflecting increased interionic interactions.
What is the activity of a pure solid or liquid when included in an equilibrium constant expression?
Answer: It is equal to one.
The activity of pure solids and liquids is conventionally taken as unity, meaning they do not explicitly appear in equilibrium constant expressions.
Which type of equilibrium occurs when all reactants and products are in the same physical phase?
Answer: Homogeneous equilibrium
Homogeneous equilibrium is defined as occurring when all reactants and products are present in the same physical phase (e.g., all gases or all dissolved in a single solution).
Which of the following is NOT a valid approach for calculating the composition of a mixture at equilibrium?
Answer: Maximizing the system's enthalpy.
Calculating equilibrium composition typically involves minimizing Gibbs free energy, manipulating equilibrium constants, or satisfying mass-balance equations; maximizing enthalpy is not a standard approach for determining equilibrium.
What is the role of Lagrange multipliers in calculating equilibrium compositions?
Answer: To solve the constrained minimization of Gibbs free energy.
Lagrange multipliers are mathematical tools used to solve the constrained optimization problem of minimizing the Gibbs free energy subject to conservation laws (mass balance).
For gas-phase reactions, what term is used instead of activity to account for non-ideal behavior?
Answer: Fugacity
For gas-phase reactions, fugacity is used as the thermodynamic variable to account for non-ideal behavior, analogous to how activity coefficients adjust concentrations in solutions.
What is the relationship between Kc and the ionic strength in solutions?
Answer: Kc can vary with ionic strength due to changes in activity coefficients.
The concentration-based equilibrium constant (Kc) can vary with ionic strength because ionic strength influences the activity coefficients of the reacting species.
The Boudouard reaction involves the equilibrium between carbon monoxide, carbon dioxide, and solid carbon.
Answer: True
The Boudouard reaction describes the equilibrium between carbon monoxide, carbon dioxide, and solid carbon, represented as 2 CO(g) <=> CO2(g) + C(s).
The Haber-Bosch process involves only a single equilibrium step: the direct reaction between nitrogen and hydrogen.
Answer: False
The Haber-Bosch process is a complex industrial synthesis involving multiple equilibrium steps, including adsorption, dissociation, reaction, and desorption on a catalyst surface.
The equilibrium constant expression for the Boudouard reaction includes a term for solid carbon.
Answer: False
The equilibrium constant expression for the Boudouard reaction excludes solid carbon because its activity is considered unity.
The self-ionization constant of water (Kw) is defined as the ratio of hydronium ion concentration to hydroxide ion concentration.
Answer: False
The self-ionization constant of water (Kw) is defined as the product of the hydronium ion concentration and the hydroxide ion concentration.
Multiple equilibria, like those in polybasic acids, can be calculated by multiplying the individual stepwise equilibrium constants.
Answer: True
For processes involving multiple sequential equilibria, such as the dissociation of polybasic acids, the overall equilibrium constant is the product of the individual stepwise equilibrium constants.
The hydrolysis of aluminum ions (Al3+) shows complex equilibrium behavior, including precipitation and the formation of soluble aluminate ions at different pH levels.
Answer: True
The hydrolysis of aluminum ions illustrates complex equilibrium behavior, demonstrating how pH changes can lead to precipitation of aluminum hydroxide and the formation of soluble aluminate species.
The self-ionization of water is represented by the equilibrium 2 H2O <=> H3O+ + OH-. What is Kw?
Answer: Kw = [H3O+] * [OH-]
The ion product constant for water (Kw) is defined as the product of the molar concentrations of hydronium ([H3O+]) and hydroxide ([OH-]) ions.
How are multiple equilibrium constants combined for a process that occurs in sequential steps?
Answer: They are multiplied together.
For a process composed of sequential steps, the overall equilibrium constant is the product of the equilibrium constants for each individual step.
The Boudouard reaction equilibrium constant expression is Kc = [CO2] / [CO]^2. Why is solid carbon excluded?
Answer: Because solid carbon's activity is considered one.
Solid carbon is a pure substance and its activity is taken as unity, hence it is omitted from the equilibrium constant expression for the Boudouard reaction.
The Haber-Bosch process for ammonia synthesis is given as an example of:
Answer: A process involving multiple equilibrium steps.
The Haber-Bosch process, used for ammonia synthesis, is a complex industrial process that involves multiple sequential equilibrium steps, including adsorption and surface reactions.
The Curtin-Hammett principle states that equilibrium product ratios are determined solely by the relative thermodynamic stability of the products.
Answer: False
The Curtin-Hammett principle addresses situations where product ratios are determined by the relative stability of transition states leading to products, particularly when secondary reactions occur.
A metastable mixture is a system that has reached its true thermodynamic equilibrium state.
Answer: False
A metastable mixture is kinetically stable but not thermodynamically stable; it has not reached its true equilibrium state due to a kinetic barrier.
Which statement accurately describes the Curtin-Hammett principle?
Answer: It relates product ratios to transition state stability when secondary reactions occur.
The Curtin-Hammett principle addresses situations where product ratios are determined by the relative stability of transition states leading to products, particularly when secondary reactions occur.
What is a 'metastable mixture'?
Answer: A mixture that appears stable but has a kinetic barrier preventing true equilibrium.
A metastable mixture is one that seems stable but is not at its lowest possible energy state; a kinetic barrier prevents it from reaching true thermodynamic equilibrium.