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Ch.16 - Chemical Equilibrium
Tro - Chemistry: A Molecular Approach 6th Edition
Tro6th EditionChemistry: A Molecular ApproachISBN: 9780137832217Not the one you use?Change textbook
All textbooksTro 6th EditionCh.16 - Chemical EquilibriumProblem 40
Chapter 16, Problem 40

Consider the following reaction: H2(g) + I2(g) ⇌ 2 HI(g) Complete the table. Assume that all concentrations are equilibrium concentrations in M.
T (°C) [H2] [I2] [HI] Kc
25 0.0355 0.0388 0.922 _
340 _ 0.0455 0.387 9.6
445 0.0485 0.0468 _ 50.2

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1
Identify the balanced chemical equation for the reaction: H2(g) + I2(g) ⇌ 2 HI(g).
Use the equilibrium constant expression for the reaction, Kc = \(\frac{[HI]^2}{[H2][I2]}\), to set up the equation for each scenario provided in the table.
For each row in the table, substitute the given equilibrium concentrations of H2, I2, and HI into the Kc expression.
Calculate Kc by solving the expression for each set of concentrations. Remember to square the concentration of HI since it has a coefficient of 2 in the balanced equation.
Ensure the units are consistent and that all concentrations are in moles per liter (M) before substituting them into the Kc expression.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Chemical Equilibrium

Chemical equilibrium occurs when the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. In the given reaction, H2 and I2 combine to form HI, and at equilibrium, the concentrations of all species remain unchanged over time. Understanding this concept is crucial for analyzing the provided equilibrium concentrations and calculating the equilibrium constant (Kc).
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Equilibrium Constant (Kc)

The equilibrium constant (Kc) is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium, raised to the power of their stoichiometric coefficients. For the reaction H2(g) + I2(g) ⇌ 2 HI(g), Kc is calculated as [HI]^2 / ([H2][I2]). This constant provides insight into the position of equilibrium and how it shifts with changes in concentration or temperature.
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Le Chatelier's Principle

Le Chatelier's Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the system will adjust to counteract the change and restore a new equilibrium. This principle helps predict how changes in temperature, pressure, or concentration will affect the equilibrium position of the reaction. In the context of the question, understanding this principle is essential for interpreting how Kc values might vary with temperature.
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Related Practice
Textbook Question

Consider the reaction: SO2Cl2(g) ⇌ SO2(g) + Cl2(g) Kp = 2.91*10^3 at 298 K In a reaction at equilibrium, the partial pressure of SO2 is 117 torr and that of Cl2 is 205 torr. What is the partial pressure of SO2Cl2 in this mixture?

Textbook Question

Consider the reaction: N2(g) + 3 H2(g) ⇌ 2 NH3(g) Complete the table. Assume that all concentrations are equilibrium concentrations in M.

T (K) [N2] [H2] [NH3] Kc

500 0.115 0.105 0.439 _

575 0.110 _ 0.128 9.6

775 0.120 0.140 _ 0.0584

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Textbook Question

Consider the reaction:

2 NO( g) + Br2( g)Δ2 NOBr( g) Kp = 28.4 at 298 K

In a reaction mixture at equilibrium, the partial pressure of NO is 125 torr and that of Br2 is 148 torr. What is the partial pressure of NOBr in this mixture?