Textbook Question
Consider the following equilibrium between oxides of nitrogen 3 NO(g) ⇌ NO2(g) + N2O(g) (a) Use data in Appendix C to calculate ΔH° for this reaction.
Ch.15 - Chemical Equilibrium
Chapter 15, Problem 65c
Consider the following equilibrium between oxides of nitrogen
3 NO(g) ⇌ NO2(g) + N2O(g)
(c) At constant temperature, would a change in the volume of the container affect the fraction of products in the equilibrium mixture?
Verified step by step guidance1
Identify the reaction: 3 NO(g) ⇌ NO2(g) + N2O(g). This is a gaseous equilibrium reaction involving nitrogen oxides.
Apply Le Chatelier's Principle, which states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change.
Consider the effect of volume change: Decreasing the volume of the container increases the pressure, while increasing the volume decreases the pressure.
Count the moles of gas on each side of the equilibrium: On the left side, there are 3 moles of NO(g), and on the right side, there are 1 mole of NO2(g) and 1 mole of N2O(g), totaling 2 moles.
Determine the shift in equilibrium: A decrease in volume (increase in pressure) will shift the equilibrium towards the side with fewer moles of gas, which is the right side (products), increasing the fraction of products. Conversely, an increase in volume (decrease in pressure) will shift the equilibrium towards the left side (reactants), decreasing the fraction of products.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Le Chatelier's Principle
Le Chatelier's Principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change. In the context of gas reactions, changes in volume can affect the concentrations of reactants and products, prompting the system to adjust in order to restore equilibrium.
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Le Chatelier's Principle
Equilibrium Constant (K)
The equilibrium constant (K) is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. For the reaction 3 NO(g) ⇌ NO<sub>2</sub>(g) + N<sub>2</sub>O(g), K can be calculated using the concentrations of NO<sub>2</sub> and N<sub>2</sub>O divided by the concentration of NO raised to the power of three, indicating the extent of the reaction at equilibrium.
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Effect of Volume on Gas Equilibria
Changing the volume of a container affects the pressure and concentration of gaseous reactants and products. For reactions involving gases, decreasing the volume increases pressure, which can shift the equilibrium position towards the side with fewer moles of gas, while increasing the volume has the opposite effect. In this case, understanding the mole ratio of gases involved is crucial to predict the direction of the shift.
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Related Practice
Textbook Question
Methanol (CH3OH) can be made by the reaction of CO with H2: CO(𝑔) + 2 H2(𝑔) ⇌ CH3OH(𝑔) (a) Use thermochemical data in Appendix C to calculate ΔH° for this reaction.
Textbook Question
Methanol (CH3OH) can be made by the reaction of CO with H2: CO(𝑔) + 2 H2(𝑔) ⇌ CH3OH(𝑔) (b) To maximize the equilibrium yield of methanol, would you use a high or low temperature?
Textbook Question
Methanol (CH3OH) can be made by the reaction of CO with H2: CO(𝑔) + 2 H2(𝑔) ⇌ CH3OH(𝑔) (c) To maximize the equilibrium yield of methanol, would you use a high or low pressure?