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Chemical Equilibrium Basics Quiz
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Chemical Equilibrium Basics Quiz

Created by
@ProdigiousSerpentine6835

Questions and Answers

Why are pure solids and liquids not included in equilibrium constant expressions?

  • They are not considered part of the equilibrium.
  • Their concentrations change depending on the reaction.
  • They do not affect the position of equilibrium.
  • Their concentrations are fixed by their density and molar mass. (correct)

    • What unit is used for equilibrium constants Kc and Kp?

  • Dimensionless. (correct)
  • Pressure only.
  • Molarity only.
  • It varies depending on the reaction.

    • What defines homogeneous equilibrium?

  • Reactants and products exist in different phases.
  • Temperature is independent of the concentrations of reactants and products.
  • Reactants and products exist in the same phase. (correct)
  • Concentrations of all species are variable.

    • Which equation relates Kp and Kc for a gaseous reaction?

    <p>Kp = Kc(RT)∆n</p> Signup and view all the answers

    What must be specified when quoting Kc?

    <p>The balanced equation and temperature.</p> Signup and view all the answers

    Which of the following statements about equilibrium constants is incorrect?

    <p>Kp is always equal to Kc.</p> Signup and view all the answers

    In the reaction aA + bB ↔ cC + dD, ∆n represents what?

    <p>The difference in moles of reactants and products.</p> Signup and view all the answers

    What can affect the position of equilibrium in a reaction?

    <p>Temperature.</p> Signup and view all the answers

    For the reaction 2NO2 (g) ↔ 2NO (g) + O2 (g) at 1000K, what is the provided value of Kc?

    <p>158</p> Signup and view all the answers

    What does the equilibrium constant Kc depend on?

    <p>The stoichiometric coefficients and temperature</p> Signup and view all the answers

    Which of the following is true about the equilibrium constant (Kc, Keq)?

    <p>It remains constant for a given reaction at a specific temperature.</p> Signup and view all the answers

    What does the Law of Mass Action state regarding chemical reactions?

    <p>The rate of a chemical reaction is proportional to the mass/concentration of reactants.</p> Signup and view all the answers

    What characterizes ionic bonds according to the content?

    <p>They consist of the removal of valence electrons and the addition of electrons to a partly filled shell.</p> Signup and view all the answers

    Given PNO2 = 0.400 atm and PNO = 0.270 atm, what is required to determine the equilibrium pressure of O2?

    <p>The value of Kc</p> Signup and view all the answers

    Which statement is a correct implication of the equilibrium constant?

    <p>It describes the extent to which reactants are converted to products at equilibrium.</p> Signup and view all the answers

    What remains constant in a chemical equilibrium system despite changes in concentration or pressure?

    <p>Equilibrium constant (Kc)</p> Signup and view all the answers

    In the context of multiple equilibria, how can one express Kc for an overall reaction?

    <p>As a product of individual equilibrium constants</p> Signup and view all the answers

    In which of the following scenarios can the reaction represented as $H_2O (l) ightarrow H_2O (g)$ be carried out?

    <p>Under atmospheric conditions.</p> Signup and view all the answers

    What represents the ratio of the rate constants of the forward and reverse reactions?

    <p>Kc</p> Signup and view all the answers

    What role does the equilibrium constant play in a chemical reaction?

    <p>It relates the concentrations of reactants and products at equilibrium.</p> Signup and view all the answers

    What is the relationship between Kf and Kb in a chemical reaction at equilibrium?

    <p>Kf = Kb at equilibrium only</p> Signup and view all the answers

    Which of the following statements about covalent bonds is accurate?

    <p>They involve the sharing of pairs of valence electrons between atoms.</p> Signup and view all the answers

    What is the value of K’c for carbonic acid (H2CO3) at 25°C?

    <p>4.2 x 10-7</p> Signup and view all the answers

    Which characteristic distinguishes the ionic bond from other types of bonds?

    <p>Ionic bonds form between atoms with large differences in electronegativity.</p> Signup and view all the answers

    What occurs when the initial concentrations of reactants are equal in an equilibrium expression for Kc?

    <p>The quadratic expression will be a perfect square.</p> Signup and view all the answers

    If Kc is greater than Qc, what will happen to the system?

    <p>The net reaction will proceed forward.</p> Signup and view all the answers

    In the equation ax² + bx + c = 0, what method is used if the expression for Kc is not a perfect square?

    <p>Two computations are needed.</p> Signup and view all the answers

    What is the significance of the equilibrium constant Kc in the reaction H2 (g) + I2 (g) ↔ 2HI (g) at 430°C?

    <p>It measures the ratio of products to reactants at equilibrium.</p> Signup and view all the answers

    When converting initial concentrations in moles to molarity (M), which calculation is applied?

    <p>Divide the number of moles by the volume in liters.</p> Signup and view all the answers

    Given a mixture of 0.500 mol of H2 and 0.500 mol of I2 in a 1.00-L flask, what is the molarity of H2?

    <p>0.500 M</p> Signup and view all the answers

    What is the value of the equilibrium constant Kc for the reaction N2(g) + 3H2(g) ↔ 2NH3(g) given in the content?

    <p>2.37 x 10-3</p> Signup and view all the answers

    What must be true about the initial concentrations for the quadratic equation to be used in Kc calculations?

    <p>They should be equal.</p> Signup and view all the answers

    What is the equilibrium expression for the reaction N2(g) + 3H2(g) ↔ 2NH3(g)?

    <p>$K_c = \frac{[NH3]^2}{[N2][H2]^3}$</p> Signup and view all the answers

    What will happen to the equilibrium position if the concentration of NH3 is increased from 1.05 M to 3.65 M?

    <p>The equilibrium will shift to the left</p> Signup and view all the answers

    Given the equilibrium constant Kc at 720°C is 2.37 x 10-3, what does a higher reaction quotient Qc of 2.86 x 10-2 indicate?

    <p>The reaction favors the reactants</p> Signup and view all the answers

    What is the calculated value of Kc at equilibrium based on the concentrations of the products and reactants?

    <p>53.96</p> Signup and view all the answers

    In the reaction N2(g) + 3H2(g) ↔ 2NH3(g), if 0.500 - x is multiplied by 7.37, what does it signify?

    <p>It is the concentration of H2 at equilibrium</p> Signup and view all the answers

    Which of the following statements correctly describes the relationship between Kc and Qc?

    <p>Kc is constant at a given temperature, while Qc can change</p> Signup and view all the answers

    What is the interpretation if the computed Kc (53.96) is within ±1 of the given Kc (54.3)?

    <p>The equilibrium condition is acceptable</p> Signup and view all the answers

    What key factor does Le Chatelier’s principle emphasize in predicting the direction of equilibrium shifts?

    <p>Concentration changes of reactants and products</p> Signup and view all the answers

    Study Notes

    Chemical Equilibrium Basics

    • Definition: A dynamic state where the rate of the forward reaction equals the rate of the reverse reaction.
    • Types of Reactions: Can be studied under atmospheric conditions and function selectively for specific types.

    Law of Mass Action

    • Key Principle: The rate of a chemical reaction is proportional to the concentration of reactants.
    • Equilibrium Constant (Kc): Constant at a given temperature, relating concentrations of reactants and products at equilibrium.
    • Expression: ( K_c = \frac{[C]^c[D]^d}{[A]^a[B]^b} ) where [C], [D], [A], and [B] are concentrations of products and reactants, respectively.

    Equilibrium Types

    • Homogeneous Equilibrium: All reactants and products are in the same phase (e.g., gases in a reaction).
    • Heterogeneous Equilibrium: Reactants and products exist in different phases (e.g., solids in a reaction).

    Factors Affecting Equilibrium

    • Temperature Dependence: Kc is dependent on temperature, while initial concentrations do not influence the equilibrium constant.
    • Concentration of Pure Solids and Liquids: Their concentrations are fixed and not included in Kc expressions due to constancy.

    Relationships Between Equilibrium Constants

    • Kc vs. Kp: ( Kp = Kc(RT)^{\Delta n} ), where Δn is the change in moles of gas between products and reactants.
    • Multiple Equilibria: The overall ( K_c ) can be found by multiplying the ( K_c ) values of individual reactions.

    Equilibrium Calculations

    • Calculating Kc from Concentrations: Use equilibrium concentrations to find Kc, which should be a constant for a specific reaction at a defined temperature.
    • Le Chatelier's Principle: Predicts the direction of the equilibrium shift in response to changes in concentration, pressure, or temperature.

    Sample Equilibrium Reaction Analysis

    • For the reaction: ( N_2(g) + 3H_2(g) \leftrightarrow 2NH_3(g) ):
      • Given ( K_c = 2.37 \times 10^{-3} ) at 720°C.
      • Compute equilibrium concentrations from initial values.

    Changes in Concentration

    • When concentrations change (e.g., adding NH3), calculate Qc to determine the direction of equilibrium shift.
    • If ( Q_c > K_c ), the equilibrium shifts left; if ( Q_c < K_c ), it shifts right.

    Important Equilibrium Concepts

    • Equilibrium Constant (Kc): Dimensionless and value varies with temperature.
    • Stoichiometry for Equilibrium: Use stoichiometric relationships to determine changes in concentrations.
    • Computational Methods: Use quadratic equations when the Kc expression doesn't yield simple square roots.

    Example Computation Process

    • Equilibrium reaction example:
      • Initial concentrations provided, relate them to changes (using ( x )).
      • Perform calculations to solve for unknown concentrations at equilibrium.
      • Check computed ( K_c ) against the provided value for accuracy.

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    Description

    Test your knowledge on the fundamentals of chemical equilibrium, including definitions and key principles such as the law of mass action. Explore the concepts of equilibrium constants and the different types of equilibria. Understand how various factors influence the state of equilibrium in chemical reactions.

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