Chemical Equilibrium Quiz
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Questions and Answers

What condition must be met for a chemical system to be in dynamic equilibrium?

  • The system must have only reactants present.
  • The concentrations of reactants must be equal to the concentrations of products.
  • The rates of the forward and reverse reactions must be equal. (correct)
  • The reaction must proceed only in the forward direction.

    • In the ICE table, what does the '-X' signify?

  • The change in concentration of reactants. (correct)
  • The equilibrium constant of the reaction.
  • The initial amount of reactants.
  • The total concentration at equilibrium.

    • How is the equilibrium constant (Kc) calculated?

  • The sum of the concentrations of products divided by the sum of the concentrations of reactants.
  • The product of the concentrations of products raised to their stoichiometric coefficients, divided by reactants raised to theirs. (correct)
  • The difference between reactant and product concentrations.
  • The average concentrations of all reactants and products.

    • What does it indicate if Kc is much larger than 1?

    <p>The products are favored at equilibrium. (A)</p> Signup and view all the answers

    What occurs if the reaction quotient Q is greater than Kc?

    <p>The reaction will shift to favor reactants. (B)</p> Signup and view all the answers

    Which substances are excluded from the equilibrium constant expression Kc?

    <p>Only pure liquids and solids. (C)</p> Signup and view all the answers

    What is the role of stoichiometry in equilibrium calculations?

    <p>It helps in determining the coefficients for the equilibrium expression. (D)</p> Signup and view all the answers

    When using the ICE table, how do you calculate the equilibrium concentration?

    <p>Initial concentration plus change represented by the equilibrium shift. (C)</p> Signup and view all the answers

    Which statement about the reaction quotient Q is false?

    <p>Q provides no insight into the direction of the reaction. (C)</p> Signup and view all the answers

    How do equilibrium calculations differ from unidirectional reactions?

    <p>They involve calculating concentrations of reactants and products at equilibrium. (C)</p> Signup and view all the answers

    Flashcards

    Chemical Equilibrium

    The point at which the rates of the forward and reverse reactions are equal, resulting in no net change in the concentrations of reactants and products. The system appears inactive, but reactions are still happening.

    ICE table

    A table used to solve equilibrium calculations by organizing initial concentrations, changes, and equilibrium concentrations.

    Equilibrium Constant (Kc)

    A constant that indicates the relative amounts of reactants and products at equilibrium for a particular reaction. It is calculated by dividing the product of product concentrations (raised to their stoichiometric coefficients) by the product of reactant concentrations.

    Reaction Quotient (Q)

    A measure of the relative amounts of products and reactants at any given moment, even if the system is not at equilibrium. It is calculated using the same formula as Kc but with non-equilibrium concentrations.

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    Q vs. Kc

    If Q < Kc, the system will shift to the right (towards products) to reach equilibrium. If Q > Kc, the system will shift to the left (towards reactants). If Q = Kc, the system is already at equilibrium.

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    Calculating Equilibrium Concentrations

    The process of determining the concentrations of all reactants and products at equilibrium using the Kc expression and the ICE table.

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    Limiting Reactant

    A reactant that is completely consumed in a reaction, limiting the amount of product that can form.

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    Theoretical Yield

    The theoretical amount of product that could be formed if the reaction goes to completion.

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    Le Chatelier's Principle

    The direction a reaction will shift to reach equilibrium if the system is disturbed. These disturbances include changes in concentration, temperature, or pressure.

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    Solids and Pure Liquids in Kc

    Solids and pure liquids do not affect the equilibrium constant (Kc) because their concentrations (or activities) remain essentially constant.

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    Study Notes

    Chemical Equilibrium

    • Chemical reactions can proceed in both forward and reverse directions.
    • When the rates of the forward and reverse reactions are equal, the system is in a state of dynamic equilibrium.
    • While chemical reactions occur in equilibrium, the system appears inactive because the forward and reverse reactions happen at the same rate.
    • Stoichiometry helps calculate the limiting reactant and the expected product yield in unidirectional reactions.
    • Equilibrium calculations are more complex as they involve determining the concentration of each substance at equilibrium.

    ICE Table

    • The ICE (Initial, Change, Equilibrium) table helps organize and solve equilibrium calculations.
    • Fill the table with the initial amount of each substance.
    • Use -X to represent the change in concentration for reactants and +X for products.
    • The coefficients in the balanced equation are used to determine the change in concentration.
    • The equilibrium concentration is the sum of the initial concentration and the change.

    Equilibrium Constant (Kc)

    • Each equilibrium reaction has a specific equilibrium constant (Kc).
    • Kc is calculated by multiplying the concentrations of products, each raised to their stoichiometric coefficient, and dividing by the product of the concentrations of reactants, each raised to their stoichiometric coefficient.
    • Kc indicates the relative amounts of products and reactants at equilibrium.
    • If Kc is much larger than 1, the products predominate at equilibrium.
    • If Kc is much smaller than 1, the reactants dominate at equilibrium.
    • Solids and pure liquids are not included in the Kc expression.

    Reaction Quotient (Q)

    • Q can be calculated by substituting non-equilibrium concentrations into the Kc expression.
    • If Q is less than Kc, the reaction will shift to the product side to reach equilibrium.
    • If Q is greater than Kc, the reaction will shift to the reactant side to reach equilibrium.
    • If Q is equal to Kc, the system is already at equilibrium.

    Calculating Equilibrium Concentrations

    • Using the ICE table and the Kc expression allows for the calculation of equilibrium concentrations.
    • Substitute the equilibrium concentrations into the Kc expression and solve for X.
    • The value of X can then be used to determine the equilibrium concentrations of all substances.

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    Description

    Test your knowledge on chemical equilibrium concepts, including dynamic equilibrium, stoichiometry, and ICE tables. This quiz will challenge you to solve problems related to equilibrium calculations, helping you understand the balance of chemical reactions.

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