Textbook Question
For the following equilibria, use Le Châtelier's principle to predict the direction of the reaction when the pressure is increased by decreasing the volume of the equilibrium mixture.
a. C(s) + H2O(g) ⇌ CO(g) + H2(g)
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Ch.7 Chemical Reactions: Energy, Rate and Equilibrium
McMurry8th EditionFundamentals of GOBISBN: 9780134015187
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Table of contents
- Ch.1 Matter and Measurements27
- Ch.2 Atoms and the Periodic Table20
- Ch.3 Ionic Compounds8
- Ch.4 Molecular Compounds23
- Ch.5 Classification & Balancing of Chemical Reactions12
- Ch.6 Chemical Reactions: Mole and Mass Relationships28
- Ch.7 Chemical Reactions: Energy, Rate and Equilibrium64
- Ch.8 Gases, Liquids and Solids24
- Ch.9 Solutions52
- Ch.10 Acids and Bases25
- Ch.11 Nuclear Chemistry22
- Ch.12 Introduction to Organic Chemistry: Alkanes57
- Ch.13 Alkenes, Alkynes, and Aromatic Compounds47
- Ch.14 Some Compounds with Oxygen, Sulfur, or a Halogen50
- Ch.15 Aldehydes and Ketones45
- Ch.16 Amines42
- Ch.17 Carboxylic Acids and Their Derivatives57
- Ch.18 Amino Acids and Proteins82
- Ch.19 Enzymes and Vitamins63
- Ch.20 Carbohydrates44
- Ch.21 The Generation of Biochemical Energy65
- Ch.22 Carbohydrate Metabolism45
- Ch.23 Lipids42
- Ch.24 Lipid Metabolism33
- Ch.25 Protein and Amino Acid Metabolism24
- Ch.26 Nucleic Acids and Protein Synthesis45
Chapter 7, Problem 65c
The reaction H2(g) + I2(g) ⇌ 2 HI(g) has ∆H = -2.2 kcal/mol (-9.2 kJ/mol). Will the equilibrium concentration of HI increase or decrease when
c. A catalyst is added?
Verified step by step guidance1
Understand the role of a catalyst: A catalyst speeds up the rate of a chemical reaction by lowering the activation energy, but it does not affect the position of equilibrium or the concentrations of reactants and products at equilibrium.
Recall Le Chatelier's Principle: This principle states that if a system at equilibrium is disturbed, the system will adjust to minimize the disturbance and re-establish equilibrium. However, adding a catalyst does not count as a disturbance to the equilibrium conditions.
Analyze the effect of the catalyst: Since a catalyst does not change the ∆H (enthalpy change) of the reaction or the equilibrium constant (K), it will not alter the equilibrium concentrations of H₂, I₂, or HI.
Conclude the impact on HI concentration: Adding a catalyst will not increase or decrease the equilibrium concentration of HI. It will only allow the system to reach equilibrium faster if it is not already at equilibrium.
Summarize: The equilibrium concentration of HI will remain unchanged when a catalyst is added.
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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 the system can shift in response to changes in conditions, such as concentration, temperature, or pressure.
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03:42
Chemical Equilibrium Concept 1
Catalysts
A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It works by lowering the activation energy required for the reaction to occur. Importantly, while catalysts speed up the attainment of equilibrium, they do not change the position of the equilibrium itself or the concentrations of reactants and products at equilibrium.
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1:17Coupled Reactions Example 3
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. In the context of the reaction provided, adding a catalyst does not disturb the equilibrium concentrations of H2, I2, or HI, meaning the equilibrium position remains unchanged.
Related Practice
Textbook Question
The reaction CO(g) + H2O(g) ⇌ CO2(g) + H2(g) has ∆H = -9.8 kcal/mol (-41 kJ/mol). Does the amount of H2 in an equilibrium mixture increase or decrease when the temperature is decreased?
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Textbook Question
The reaction H2(g) + I2(g) ⇌ 2 HI(g) has ∆H = -2.2 kcal/mol (-9.2 kJ/mol). Will the equilibrium concentration of HI increase or decrease when
b. H2 is removed?
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Textbook Question
The reaction Fe3+(aq) + Cl-(aq) ⇌ FeCl2+(aq) is endothermic. How will the equilibrium concentration of FeCl2+ change when
b. Cl- is precipitated by addition of AgNO3?
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Textbook Question
For the unbalanced combustion reaction shown, 1 mol of ethanol, C2H5OH, releases 327 kcal (1370 kJ):
C2H5OH + O2 → CO2 + H2O
e. If the density of ethanol is 0.789 g/mL, calculate the combustion energy of ethanol in kilocalories/milliliter and kilojoules/milliliter
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Textbook Question
For the production of ammonia from its elements, ∆H = -22 kcal/mol(-19 kJ/mol).
b. How much energy (in kilocalories and kilojoules) is involved in the production of 0.700 mol of NH3?
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