Textbook Question
(a) If Qc > Kc, how must the reaction proceed to reach equilibrium?
Ch.15 - Chemical Equilibrium
Chapter 15, Problem 44
As shown in Table 15.2, Kp for the equilibrium N2(g) + 3 H2(g) ⇌ 2 NH3(g) is 4.51 * 10^-5 at 450 _x001F_C. For each of the mixtures listed here, indicate whether the mixture is at equilibrium at 450 _x001F_C. If it is not at equilibrium, indicate the direction (toward product or toward reactants) in which the mixture must shift to achieve equilibrium. (a) 98 atm NH3, 45 atm N2, 55 atm H2. (b) 57 atm NH3, 143 atm N2, no H2. (c) 13 atm NH3, 27 atm N2, 82 atm H2.
Verified step by step guidance1
Step 1: Write the expression for the equilibrium constant Kp for the reaction N2(g) + 3 H2(g) ⇌ 2 NH3(g). The expression is Kp = (P_{NH3}^2) / (P_{N2} * P_{H2}^3), where P represents the partial pressures of the gases.
Step 2: For each mixture, calculate the reaction quotient Qp using the same expression as Kp: Qp = (P_{NH3}^2) / (P_{N2} * P_{H2}^3). Substitute the given partial pressures into this expression for each case.
Step 3: Compare the calculated Qp value with the given Kp value (4.51 * 10^-5) for each mixture. This comparison will help determine the state of the system relative to equilibrium.
Step 4: If Qp = Kp, the system is at equilibrium. If Qp < Kp, the reaction will shift toward the products (right) to reach equilibrium. If Qp > Kp, the reaction will shift toward the reactants (left) to reach equilibrium.
Step 5: Analyze each mixture: (a) Calculate Qp and compare with Kp to determine the direction of shift. (b) Calculate Qp and compare with Kp to determine the direction of shift. (c) Calculate Qp and compare with Kp to determine the direction of shift.
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Equilibrium Constant (Kp)
The equilibrium constant, Kp, quantifies the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. For the reaction N2(g) + 3 H2(g) ⇌ 2 NH3(g), Kp is calculated using the partial pressures of the gases involved. A Kp value of 4.51 * 10^-5 indicates that at equilibrium, the concentration of reactants is much higher than that of the products, suggesting that the reaction favors the formation of reactants.
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Equilibrium Constant Expressions
Le Chatelier's Principle
Le Chatelier's Principle states that if a system at equilibrium is subjected to a change in concentration, pressure, or temperature, the system will adjust to counteract that change and restore a new equilibrium. This principle helps predict the direction in which a reaction will shift when the concentrations of reactants or products are altered, allowing us to determine whether a mixture is at equilibrium or not.
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Reaction Quotient (Q)
The reaction quotient, Q, is calculated using the same formula as Kp but uses the current concentrations or partial pressures of the reactants and products, regardless of whether the system is at equilibrium. By comparing Q to Kp, one can determine the direction in which the reaction will shift: if Q < Kp, the reaction shifts toward products; if Q > Kp, it shifts toward reactants. This comparison is essential for assessing the state of the mixtures provided in the question.
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Related Practice
Textbook Question
(b) At the start of a certain reaction, only reactants are present; no products have been formed. What is the value of Qc at this point in the reaction?
Textbook Question
At 100°C, the equilibrium constant for the reaction COCl2(𝑔) ⇌ CO(𝑔) + Cl2(𝑔) has the value 𝐾𝑐 = 2.19×10−10. Are the following mixtures of COCl2, CO, and Cl2 at 100°C at equilibrium? If not, indicate the direction that the reaction must proceed to achieve equilibrium.
(a) [COCl2] = 2.00×10−3 M, [CO] = 3.3×10−6 M, [Cl2] = 6.62×10−6 M
(b) [COCl2] = 4.50×10−2 M, [CO] = 1.1×10−7 M, [Cl2] = 2.25×10−6 M
(c) [COCl2] = 0.0100 M, [CO] = [Cl2] = 1.48×10−6 M
Textbook Question
At 900 K, the following reaction has 𝐾𝑝 = 0.345: 2 SO2(𝑔) + O2(𝑔) ⇌ 2 SO3(𝑔) In an equilibrium mixture the partial pressures of SO2 and O2 are 0.135 atm and 0.455 atm, respectively. What is the equilibrium partial pressure of SO3 in the mixture?