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Chemical Equilibria

The Equilibrium Constant Kc

  • 3 things to know
  • Papers 1, 2 and 3

Overview

Writing the Kc expression, calculating it from equilibrium amounts, and working out its units.

What you need to know

Answer each one before you reveal it.

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Key term

What is the equilibrium constant Kc?

Key term

For a reversible reaction at equilibrium, what does the expression for Kc contain?

Key term

How are stoichiometric coefficients incorporated into a Kc expression?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is the equilibrium constant Kc?

    Model answer

    A constant that expresses the ratio of product concentrations to reactant concentrations at equilibrium, each raised to the power of their stoichiometric coefficients

  2. 2

    For a reversible reaction at equilibrium, what does the expression for Kc contain?

    Model answer

    The equilibrium concentrations of products and reactants

  3. 3

    In a Kc expression, where do the concentrations of products appear?

    Model answer

    In the numerator

  4. 4

    In a Kc expression, where do the concentrations of reactants appear?

    Model answer

    In the denominator

  5. 5

    How are stoichiometric coefficients incorporated into a Kc expression?

    Model answer

    Each concentration is raised to the power of its stoichiometric coefficient in the balanced equation

  6. 6

    What are the units of Kc?

    Model answer

    The units depend on the stoichiometry of the reaction and must be worked out for each equilibrium

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