7.2 Calculating the Equilibrium Constant

• What is the equilibrium constant (K) a quantitative measure of?

  Extent of a chemical reaction
• What information does the value of K provide about a reaction at equilibrium?

  Extent and direction
• Match the term with its explanation:

  K ↔️ Equilibrium constant expression

  [C] and [D] ↔️ Equilibrium concentrations of products

  c and d ↔️ Stoichiometric coefficients of products
• The equilibrium constant expression is given by K = \frac{[C]^{c}[D]^{d}}{[A]^{a}[B]^{b}}</latex>, where [A], [B], [C], and [D] represent equilibrium concentrations
• What do [A] and [B] represent in the equilibrium constant expression?

  Equilibrium concentrations of reactants
• What is the first step in balancing a chemical equation?

  Write the unbalanced equation
• For the reaction $N_{2}(g) +$$3H_{2}(g) \rightleftharpoons 2NH_{3}(g)$, if the initial concentrations of $[N_{2}]_{0} =$$1.0 M$ and $[H_{2}]_{0} =$$3.0 M$, and $K =$$4.0$, then the equilibrium concentration of NH₃ is 1.0 M.


  True
• The equilibrium constant (K) is a quantitative measure of the extent of a chemical reaction at equilibrium.

  True
• The equilibrium constant expression for the reaction $N_{2}(g) +$$3H_{2}(g) \rightleftharpoons 2NH_{3}(g)$ is K = \frac{[NH_{3}]^{2}}{[N_{2}][H_{2}]^{3}}</latex>.


  True
• How is the equilibrium constant (K) defined in terms of chemical reactions?

  Ratio of product to reactant concentrations
• Pressure changes affect K only if the number of moles of gas is unequal
• The stoichiometric coefficients in the equilibrium constant expression are exponents
• To write a balanced chemical equation, the first step is to write the unbalanced equation.
• Steps to balance a chemical equation

  1️⃣ Write the unbalanced equation

  2️⃣ Count atoms on both sides

  3️⃣ Adjust stoichiometric coefficients

  4️⃣ Verify all atoms are balanced
• Equilibrium concentrations are found by summing the initial and change concentrations.
• In the example, the equilibrium concentration of $N_{2}$ is $0.5 M$.


  True
• Substituting equilibrium concentrations into the equilibrium constant expression allows for the calculation of the value of K.


  True
• What is the equilibrium constant expression for the reaction $N_{2}(g) +$$3H_{2}(g) \rightleftharpoons 2NH_{3}(g)$?


  $K =$$\frac{[NH_{3}]^{2}}{[N_{2}][H_{2}]^{3}}$
• The ICE table is used to calculate equilibrium concentrations in a reaction.


  True
• In the change row of the ICE table, the changes for N₂, H₂, and NH₃ are -x, -3x, and +2x, respectively.
• If x ≈ 0.5, what is the equilibrium concentration of N₂?

  0.5 M
• Match the range of K with its significance:

  K > 1000 ↔️ High product formation

  K < 0.001 ↔️ Low product formation

  0.001 < K < 1000 ↔️ Reactants and products are comparable
• What happens to reactant concentrations when K is small?

  Remain unchanged
• The equilibrium constant (K) is defined as the ratio of the concentrations of the products to the reactants.
• The equilibrium constant (K) is defined as the ratio of the concentrations of the products raised to their stoichiometric coefficients.
• What do the variables [A] and [B] represent in the equilibrium constant expression?

  Reactant concentrations
• Write the steps to calculate the equilibrium constant (K) in the correct order:

  1️⃣ Write a balanced chemical equation

  2️⃣ Determine the equilibrium concentrations of reactants and products

  3️⃣ Substitute concentrations into the equilibrium constant expression

  4️⃣ Calculate the value of K

  5️⃣ Analyze the magnitude of K and its significance
• Match the term with its explanation:

  [C], [D] ↔️ Equilibrium concentrations of products

  c, d ↔️ Stoichiometric coefficients
• For the reaction $N_{2}(g) +$$3H_{2}(g) \rightleftharpoons 2NH_{3}(g)$, the equilibrium constant expression is $K =$$\frac{[NH_{3}]^{2}}{[N_{2}][H_{2}]^{3}}$, which shows that [NH₃] is raised to the power of 2
• Steps to determine equilibrium concentrations using an ICE table:

  1️⃣ Write the balanced chemical equation

  2️⃣ Set up the ICE table

  3️⃣ Calculate changes in concentrations

  4️⃣ Determine equilibrium concentrations

  5️⃣ Substitute into the equilibrium constant expression
• For the reaction $N_{2}(g) +$$3H_{2}(g) \rightleftharpoons 2NH_{3}(g)$, if K = 4.0</latex> and the initial concentrations are $[N_{2}]_{0} =$$1.0 M$ and $[H_{2}]_{0} =$$3.0 M$, the equilibrium concentration of H₂ is 1.5 M
• What is the initial concentration of N₂ in the reaction $N_{2}(g) +$$3H_{2}(g) \rightleftharpoons 2NH_{3}(g)$?


  $1.0 M$
• The value of x in the equilibrium calculation is approximately 0.5
• The equilibrium constant (K) is a quantitative measure of the extent of a chemical reaction at equilibrium
• What is the mathematical expression for the equilibrium constant (K) in terms of concentrations and stoichiometric coefficients?

  $K =$$\frac{[C]^{c}[D]^{d}}{[A]^{a}[B]^{b}}$
• Steps to write a balanced chemical equation

  1️⃣ Write the unbalanced equation

  2️⃣ Count the atoms of each element

  3️⃣ Adjust the stoichiometric coefficients

  4️⃣ Verify that all atoms are balanced
• When balancing a chemical equation, you must count the atoms of each element on both sides.


  True
• To determine equilibrium concentrations, the ICE table method is essential.
• What is the equilibrium constant expression for $N_{2}(g) +$$3H_{2}(g) \rightleftharpoons 2NH_{3}(g)$?


  $K =$$\frac{[NH_{3}]^{2}}{[N_{2}][H_{2}]^{3}}$
• The equilibrium concentration of NH_{3}</latex> in the example is $1.0$ M.