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Ch.15 - Chemical Equilibrium
Chapter 15, Problem 77c

Consider the hypothetical reaction A(𝑔) β‡Œ 2 B(𝑔). A flask is charged with 0.75 atm of pure A, after which it is allowed to reach equilibrium at 0Β°C. At equilibrium, the partial pressure of A is 0.36 atm. (c) To maximize the yield of product B, would you make the reaction flask larger or smaller?

Verified step by step guidance
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insert step 1> Identify the reaction: A(g) β‡Œ 2 B(g). This is a gaseous equilibrium reaction where A is converted to B.
insert step 2> Understand the concept of Le Chatelier's Principle: It states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change.
insert step 3> Consider the effect of volume change on equilibrium: Increasing the volume of the container decreases the pressure, favoring the side with more moles of gas. Conversely, decreasing the volume increases the pressure, favoring the side with fewer moles of gas.
insert step 4> Analyze the reaction: The reaction A(g) β‡Œ 2 B(g) has 1 mole of A converting to 2 moles of B. Increasing the volume will favor the formation of more moles of gas, thus shifting the equilibrium towards the products (B).
insert step 5> Conclusion: To maximize the yield of product B, you should make the reaction flask larger, as this will shift the equilibrium towards the side with more moles of gas (2 B).

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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 the reaction A(g) β‡Œ 2B(g), if the volume of the flask is altered, it affects the partial pressures of the gases, thereby influencing the equilibrium position and the yield of products.
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Equilibrium Constant (Kp)

The equilibrium constant (Kp) for a gaseous reaction is defined in terms of the partial pressures of the reactants and products at equilibrium. For the reaction A(g) β‡Œ 2B(g), Kp can be expressed as Kp = (P_B^2) / (P_A). Understanding Kp helps predict how changes in pressure or volume will affect the concentrations of A and B at equilibrium.
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Effect of Volume on Gas Equilibrium

Changing the volume of a reaction flask affects the partial pressures of gases involved in the reaction. Reducing the volume increases the pressure, favoring the side of the reaction with fewer moles of gas. In this case, since there are 2 moles of B produced for every mole of A consumed, decreasing the volume would shift the equilibrium towards producing more B, thus maximizing its yield.
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Related Practice
Textbook Question

When 2.00 mol of SO2Cl2 is placed in a 2.00-L flask at 303 K, 56% of the SO2Cl2 decomposes to SO2 and Cl2: SO2Cl2(𝑔) β‡Œ SO2(𝑔) + Cl2(𝑔) (c) According to Le ChΓ’telier's principle, would the percent of SO2Cl2 that decomposes increase, decrease or stay the same if the mixture were transferred to a 15.00-L vessel?

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Textbook Question

A sample of nitrosyl bromide (NOBr) decomposes according to the equation 2 NOBr(𝑔) β‡Œ 2 NO(𝑔) + Br2(𝑔) An equilibrium mixture in a 5.00-L vessel at 100Β°C contains 3.22 g of NOBr, 2.46 g of NO, and 6.55 g of Br2. (b) What is the total pressure exerted by the mixture of gases?

Textbook Question

A sample of nitrosyl bromide (NOBr) decomposes according to the equation 2 NOBr(𝑔) β‡Œ 2 NO(𝑔) + Br2(𝑔) An equilibrium mixture in a 5.00-L vessel at 100Β°C contains 3.22 g of NOBr, 2.46 g of NO, and 6.55 g of Br2. (c) What was the mass of the original sample of NOBr?

Textbook Question

As shown in Table 15.2, the equilibrium constant for the reaction N2(𝑔) + 3 H2(𝑔) β‡Œ 2 NH3(𝑔) is 𝐾𝑝 = 4.34Γ—10βˆ’3 at 300Β°C. Pure NH3 is placed in a 1.00-L flask and allowed to reach equilibrium at this temperature. There are 1.05 g NH3 in the equilibrium mixture. (b) What was the initial mass of ammonia placed in the vessel?

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Textbook Question

For the equilibrium PH3BCl3(𝑠) β‡Œ PH3(𝑔) + BCl3(𝑔) 𝐾𝑝 = 0.052 at 60Β°C. (b) A closed 1.500-L vessel at 60Β°C is charged with 0.0500 g of BCl3(𝑔); 3.00 g of solid PH3BCl3 is then added to the flask, and the system is allowed to equilibrate. What is the equilibrium concentration of PH3?

Textbook Question

A 0.831-g sample of SO3 is placed in a 1.00-L container and heated to 1100 K. The SO3 decomposes to SO2 and O2: 2SO3(𝑔) β‡Œ 2 SO2(𝑔) + O2(𝑔) At equilibrium, the total pressure in the container is 1.300 atm. Find the values of 𝐾𝑝 and 𝐾𝑐 for this reaction at 1100 K.

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