Open Question
When 1.000 mol of PCl5 is introduced into a 5.000-L container at 500 K, 78.50% of the PCl5 dissociates to give an equilibrium mixture of PCl5, PCl3, and Cl2: PCl5(g) ⇌ PCl3(g) + Cl2(g). (a) Calculate the values of Kc and Kp.
Ch.15 - Chemical Equilibrium
Chapter 15, Problem 106
At 100 °C, Kc = 4.72 for the reaction 2 NO21g2 ∆ N2O41g2. An empty 10.0-L flask is filled with 4.60 g of NO2 at 100 °C. What is the total pressure in the flask at equilibrium?
Verified step by step guidance1
Calculate the number of moles of NO2 initially present using the molar mass of NO2. The molar mass of NO2 is approximately 46.0 g/mol.
Use the ideal gas law to calculate the initial pressure of NO2 in the flask. The ideal gas law is PV = nRT, where P is the pressure, V is the volume, n is the number of moles, R is the gas constant (0.0821 L·atm/mol·K), and T is the temperature in Kelvin.
Set up the ICE table (Initial, Change, Equilibrium) for the reaction: 2 NO2(g) ⇌ N2O4(g). Fill in the initial concentrations, the change in concentrations as the reaction proceeds towards equilibrium, and the equilibrium concentrations.
Write the expression for the equilibrium constant Kc and substitute the equilibrium concentrations from the ICE table. Solve for the unknowns, which represent the changes in concentration due to the reaction reaching equilibrium.
Calculate the total pressure at equilibrium by adding the partial pressures of NO2 and N2O4. Use the equilibrium concentrations and the ideal gas law to find the partial pressures.
Verified Solution
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Equilibrium Constant (Kc)
The equilibrium constant, Kc, quantifies the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. For the reaction 2 NO2(g) ⇌ N2O4(g), Kc = [N2O4]/[NO2]^2. A Kc value greater than 1 indicates that at equilibrium, products are favored over reactants.
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Equilibrium Constant Expressions
Ideal Gas Law
The Ideal Gas Law relates the pressure, volume, temperature, and number of moles of a gas through the equation PV = nRT. This law is essential for calculating the total pressure in a gas system, where P is pressure, V is volume, n is the number of moles, R is the ideal gas constant, and T is temperature in Kelvin.
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Stoichiometry of Gaseous Reactions
Stoichiometry involves the quantitative relationships between reactants and products in a chemical reaction. In the context of gaseous reactions, it helps determine the moles of gases involved at equilibrium, which is crucial for calculating total pressure. Understanding the stoichiometric coefficients allows for the correct application of Kc to find equilibrium concentrations.
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Related Practice
Open Question
15.104 Consider the reaction C(s) + CO2(g) ⇌ 2 CO(g). When 1.50 mol of CO2 and an excess of solid carbon are heated in a 20.0-L container at 1100 K, the equilibrium concentration of CO is 7.00 x 10^-2 M. (a) What is the equilibrium concentration of CO2? (b) What is the value of the equilibrium constant Kc at 1100 K?
Open Question
The equilibrium constant Kp for the gas-phase thermal decomposition of tert-butyl chloride is 3.45 at 500 K: CH3C(CH3)2Cl(g) ↔ CH2=C(CH3)2(g) + HCl(g). (b) Calculate the molar concentrations of reactants and products in an equilibrium mixture obtained by heating 1.00 mol of tert-butyl chloride in a 5.00-L vessel at 500 K. (c) A mixture of isobutylene (0.400 atm partial pressure at 500 K) and HCl (0.600 atm partial pressure at 500 K) is allowed to reach equilibrium at 500 K. What are the equilibrium partial pressures of tert-butyl chloride, isobutylene, and HCl?
Open Question
At 25 °C, Kc = 216 for the reaction 2 NO2(g) ⇌ N2O4(g). A 1.00-L flask containing a mixture of NO2 and N2O4 at 25 °C has a total pressure of 1.50 atm. What is the partial pressure of each gas?
Open Question
At 500 °C, F2 gas is stable and does not dissociate, but at 840 °C, some dissociation occurs: F2(g) ⇌ 2 F(g). A flask filled with 0.600 atm of F2 at 500 °C was heated to 840 °C, and the pressure at equilibrium was measured to be 0.984 atm. What is the equilibrium constant Kp for the dissociation of F2 gas at 840 °C?
Open Question
The reaction NO(g) + NO2(g) ⇌ N2O3(g) takes place in the atmosphere with Kc = 13 at 298 K. A gas mixture is prepared with 2.0 mol NO and 3.0 mol NO2 and an initial total pressure of 1.65 atm. (a) What are the equilibrium partial pressures of NO, NO2, and N2O3 at 298 K?