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Questions and Answers
What does the subscript ‘c’ in Kc indicate?
What does the subscript ‘c’ in Kc indicate?
What happens to the equilibrium constant Kc when the stoichiometric coefficients in a reaction are multiplied by a factor?
What happens to the equilibrium constant Kc when the stoichiometric coefficients in a reaction are multiplied by a factor?
What is the relationship between the equilibrium constant Kc for a forward reaction and the equilibrium constant K'c for its reverse reaction?
What is the relationship between the equilibrium constant Kc for a forward reaction and the equilibrium constant K'c for its reverse reaction?
Why are the symbols for phases (s, l, g) generally omitted in equilibrium constant expressions?
Why are the symbols for phases (s, l, g) generally omitted in equilibrium constant expressions?
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Which of the following accurately expresses the equilibrium constant for the reaction H2(g) + I2(g) ⇌ 2HI(g)?
Which of the following accurately expresses the equilibrium constant for the reaction H2(g) + I2(g) ⇌ 2HI(g)?
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If the concentrations of reactants are increased, what will happen to the equilibrium position of a chemical reaction?
If the concentrations of reactants are increased, what will happen to the equilibrium position of a chemical reaction?
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Which factor does not affect the value of the equilibrium constant Kc?
Which factor does not affect the value of the equilibrium constant Kc?
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In an equilibrium expression for Kp, what is typically ignored?
In an equilibrium expression for Kp, what is typically ignored?
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Which of the following statements about equilibrium constants is true?
Which of the following statements about equilibrium constants is true?
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In a homogeneous equilibrium, which of the following is a necessary condition?
In a homogeneous equilibrium, which of the following is a necessary condition?
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How does an increase in temperature generally affect the value of Kc for an exothermic reaction?
How does an increase in temperature generally affect the value of Kc for an exothermic reaction?
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For the reaction N2(g) + 3H2(g) ⇌ 2NH3(g), if the concentration of NH3 is increased, what will be the immediate effect on the reaction?
For the reaction N2(g) + 3H2(g) ⇌ 2NH3(g), if the concentration of NH3 is increased, what will be the immediate effect on the reaction?
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Given the reaction CH3COOC2H5(aq) + H2O(l) ⇌ CH3COOH(aq) + C2H5OH(aq), what phase is water considered?
Given the reaction CH3COOC2H5(aq) + H2O(l) ⇌ CH3COOH(aq) + C2H5OH(aq), what phase is water considered?
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Which of the following represents a real-life example of a heterogeneous equilibrium?
Which of the following represents a real-life example of a heterogeneous equilibrium?
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If the equilibrium constant expression for the reaction aA + bB ⇌ cC + dD is Kc, what would be the expression for the reverse reaction?
If the equilibrium constant expression for the reaction aA + bB ⇌ cC + dD is Kc, what would be the expression for the reverse reaction?
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When calculating the equilibrium constant Kc for a reaction, which of the following factors is NOT needed?
When calculating the equilibrium constant Kc for a reaction, which of the following factors is NOT needed?
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What does a very large value of Kc (greater than 10^3) indicate about a chemical reaction?
What does a very large value of Kc (greater than 10^3) indicate about a chemical reaction?
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Which statement about the temperature effect on Kc is true?
Which statement about the temperature effect on Kc is true?
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In the reaction H2(g) + I2(g) ⇌ 2HI(g), if Kc is 57.0 at 700 K and the initial concentrations are [H2] = 0.10 M, [I2] = 0.20 M, and [HI] = 0.40 M, which statement is correct?
In the reaction H2(g) + I2(g) ⇌ 2HI(g), if Kc is 57.0 at 700 K and the initial concentrations are [H2] = 0.10 M, [I2] = 0.20 M, and [HI] = 0.40 M, which statement is correct?
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What happens to Kc when the reaction is reversed?
What happens to Kc when the reaction is reversed?
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What does a very small value of Kc (less than 10^-3) indicate about a chemical reaction?
What does a very small value of Kc (less than 10^-3) indicate about a chemical reaction?
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When concentration values have reached a constant value in a reaction, which condition is met?
When concentration values have reached a constant value in a reaction, which condition is met?
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For the reaction N2(g) + O2(g) ⇌ 2NO(g) at 298 K, if Kc is 4.8 × 10^-31, which conclusion can be drawn?
For the reaction N2(g) + O2(g) ⇌ 2NO(g) at 298 K, if Kc is 4.8 × 10^-31, which conclusion can be drawn?
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In a heterogeneous equilibrium, what defines the phases of reactants and products?
In a heterogeneous equilibrium, what defines the phases of reactants and products?
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Study Notes
Equilibrium
- Chemical equilibria are vital in biological and environmental processes
- Equilibria involving oxygen molecules and hemoglobin are critical for oxygen transport
- Equilibria involving carbon monoxide and hemoglobin lead to carbon monoxide toxicity
- Evaporation and condensation in a closed container result in a constant vapor pressure at equilibrium. The rate of evaporation equals the rate of condensation
- Equilibrium is dynamic, not static, with continuous activity at the boundary of phases
- Equilibrium mixture includes reactants and products in the equilibrium state
Equilibrium Processes in Physical Systems
- Equilibrium in a closed system is possible at a given temperature
- The opposing processes (e.g., evaporation and condensation) occur at the same rate
- Equilibrium is dynamic and stable
- Equilibrium is characterized by constant values of specific parameters (e.g., vapor pressure, melting point) at a specific temperature
- The parameters of a system at equilibrium show the extent of a physical process at a given temperature
- Examples: solid-liquid equilibrium (ice-water), liquid-vapor equilibrium (liquid-water vapor), solid-vapor equilibrium (sublimation of iodine)
Equilibrium Processes in Chemical Systems
- Chemical reactions also reach a dynamic equilibrium state
- For a reversible reaction, the forward and reverse reaction rates are equal when the reaction is at equilibrium
- Equilibrium is dynamic, meaning that the reaction continues in both directions even at equilibrium
- The concentrations of reactants and products remain constant at equilibrium
- Examples: Haber's process for ammonia synthesis, HI formation reaction
Law of Chemical Equilibrium and Equilibrium Constant
- Equilibrium mixtures contain reactants and products in the equilibrium state
- The ratio of product concentrations to reactant concentrations, raised to the power of their stoichiometric coefficients in a balanced chemical equation, maintains a constant value at a given temperature (equilibrium constant, K)
- This constant ratio is fixed and predictable
- Equilibrium constant value indicates the relative concentrations of products and reactants at equilibrium
- A higher equilibrium constant suggests more products at equilibrium
- K values are important for determining the extent and direction of a chemical reaction
Factors Affecting Equilibrium
- Changing concentration of a reactant or product shifts the equilibrium to counteract the change. The reaction proceeds in the direction that consumes the added reactant or produces any newly added product
- Addition of an inert gas at constant volume does not affect the partial pressures/concentrations of the reacting substances in the equilibrium mixture
- Increasing the temperature shifts the equilibrium in the direction that absorbs heat (endothermic direction)
- decreasing the temperature shifts the equilibrium in the direction that releases heat (exothermic direction)
- Addition or removal of a catalyst affects the rate of reaction but does not alter the equilibrium composition.
Ionic Equilibrium
- Acids are proton donors (Arrhenius concept) or proton donors (Brønsted-Lowry concept)
- Bases are proton acceptors (Arrhenius or Brønsted-Lowry)
- Acids and bases can be strong or weak depending on their degree of dissociation or ionization in water. Stronger acids/bases dissociate completely, while weaker ones do not
- Various theories regarding acids and bases (Arrhenius, Brønsted-Lowry, and Lewis)
- Hydronium ions (H₃O⁺) and hydroxyl ions (OH⁻) play crucial roles in acid-base reactions
- The concentration of H⁺ ions is crucial in chemical solutions and it is expressed numerically as pH
- The ionization constant of water is denoted by Kw
- Solubility product constant (Ksp) determines the solubility of sparingly soluble salts, affected by temperature or the presence of common ions
Buffer Solutions
- A buffer solution resists changes in pH when acids or bases are added
- Consists of a weak acid and its conjugate base or a weak base and its conjugate acid
Solubility Equilibrium
- The solubility product constant (Ksp) is constant for a given solid at a specific temperature
- The Ksp value indicates how soluble a given salt is at a specific temperature
- Common ion effect suppresses the solubility of a slightly soluble salt when a common ion is added to the solution
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