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Ch.15 - Chemical Equilibrium
Chapter 15, Problem 6

If Kc = 7.5 * 10^-9 at 1000 K for the reaction N2(g) + O2(g) ⇌ 2 NO(g), give the value of Kc at 1000 K for the reaction 2 N2(g) + 2 O2(g) ⇌ 4 NO(g)

Verified step by step guidance
1
Step 1: Understand that the equilibrium constant \( K_c \) is dependent on the stoichiometry of the reaction. When the coefficients of a balanced chemical equation are multiplied by a factor, the equilibrium constant is raised to the power of that factor.
Step 2: Identify the original reaction: \( \text{N}_2(g) + \text{O}_2(g) \rightleftharpoons 2 \text{NO}(g) \) with \( K_c = 7.5 \times 10^{-9} \).
Step 3: Recognize that the new reaction is \( 2 \text{N}_2(g) + 2 \text{O}_2(g) \rightleftharpoons 4 \text{NO}(g) \), which is the original reaction multiplied by 2.
Step 4: Apply the rule for modifying \( K_c \): Since the reaction is multiplied by 2, raise the original \( K_c \) to the power of 2. This means \( K_{c, \text{new}} = (K_c)^2 \).
Step 5: Substitute the given \( K_c \) value into the equation: \( K_{c, \text{new}} = (7.5 \times 10^{-9})^2 \). This will give you the new equilibrium constant for the modified reaction.
Related Practice
Open Question
Given the data for the following reactions at 298 K: N2(g) + O2(g) ⇌ 2 NO(g) Kp = 4.4 * 10^-31 NO(g) + 1/2 O2(g) ⇌ NO2(g) Kp = 1.5 * 10^6, calculate the value of the equilibrium constant Kp at 298 K for the reaction N2(g) + 2 O2(g) ⇌ 2 NO2(g). (LO 15.3) (a) Kp = 6.6 * 10^-25 (b) Kp = 1.3 * 10^-24 (c) Kp = 9.9 * 10^-19 (d) Kp = 5.4 * 10^-28
Open Question
Sulfur dioxide reacts with oxygen in a step in the production of sulfuric acid. 2 SO2(g) + O2(g) ⇌ 2 SO3(g), Kc = 7.9 * 10^4 at 1800 K. For an equilibrium mixture in which [SO2] = 4.5 * 10^-3 M and [O2] = 1.5 * 10^-3 M, what is [SO3]? (LO 15.4) (a) [SO3] = 6.2 * 10^-7 M (b) [SO3] = 4.9 * 10^-2 M (c) [SO3] = 0.73 M (d) [SO3] = 2.4 * 10^-3 M
Textbook Question
The reaction A21g2 + B21g2 ∆ 2 AB1g2 has an equilib- rium constant Kc = 9. The following figure represents a reaction mixture that contains A2 molecules (red), B2 mol- ecules (blue), and AB molecules. What statement about the mixture is true? (LO 15.5)

(a) The mixture is at equilibrium, and there will be no net shift in reaction direction. (b) The reaction will shift toward the reactants to reach equilibrium. (c) The reaction will shift toward the products to reach equilibrium. (d) More information is needed to answer this question.
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Open Question
The gas-phase reaction 2 SO2(g) + O2(g) ⇌ 2 SO3(g) has an equilibrium constant Kc = 5.8 * 10^3 at 600 °C. A mixture contains [SO2] = 0.10 M, [O2] = 0.100 M, and [SO3] = 0.200 M. Which statement is true about the reaction direction and equilibrium mixture? (LO 15.8, 15.9) (a) The mixture is at equilibrium and contains appreciable amounts of reactants and products. (b) The reaction will shift to make more product, and the equilibrium mixture contains appreciable amounts of reactants and products. (c) The reaction will shift to make more reactants, and the equilibrium mixture contains mostly product. (d) The reaction will shift to make more product, and the equilibrium mixture contains mostly reactant.
Open Question
At a temperature of 430 °C, the reaction H2(g) + I2(g) ⇌ 2 HI(g) has an equilibrium constant Kc = 54.3. Suppose that a mixture of 0.500 mol of H2(g) and 0.500 mol of I2(g) is placed into a 1.00-L stainless-steel flask at 430 °C. Calculate the concentration of HI(g) when equilibrium is reached. (LO 15.10) (a) 0.393 M (b) 0.107 M (c) 0.500 M (d) 0.786 M
Open Question
Phosphorus pentachloride decomposes to phosphorus trichloride and chlorine at high temperatures according to the equation: PCl5(g) ⇌ PCl3(g) + Cl2(g). At 250 °C, 0.250 M PCl5 is added to the flask. If Kc = 1.80, what are the equilibrium concentrations of each gas? (LO 15.11) (a) [PCl5] = 0.028 M, [PCl3] = 0.222 M, and [Cl2] = 0.222 M (b) [PCl5] = 0.125 M, [PCl3] = 0.474 M, and [Cl2] = 0.474 M (c) [PCl5] = 1.80 M, [PCl3] = 1.80 M, and [Cl2] = 1.80 M (d) [PCl5] = 2.27 M, [PCl3] = 2.02 M, and [Cl2] = 2.02 M