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Ch.15 - Chemical Equilibrium
All textbooksBrown 14th EditionCh.15 - Chemical EquilibriumProblem 91
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Chapter 15, Problem 91

An equilibrium mixture of H2, I2, and HI at 458 _x001F_C contains 0.112 mol H2, 0.112 mol I2, and 0.775 mol HI in a 5.00-L vessel. What are the equilibrium partial pressures when equilibrium is reestablished following the addition of 0.200 mol of HI?

Verified step by step guidance
1
Step 1: Write the balanced chemical equation for the reaction. The reaction between hydrogen gas (H2) and iodine gas (I2) to form hydrogen iodide (HI) is: \[ \text{H}_2(g) + \text{I}_2(g) \rightleftharpoons 2\text{HI}(g) \]
Step 2: Calculate the initial concentrations of each species in the 5.00 L vessel. Use the formula \( \text{Concentration} = \frac{\text{moles}}{\text{volume}} \). For example, the concentration of H2 is \( \frac{0.112 \text{ mol}}{5.00 \text{ L}} \). Repeat for I2 and HI.
Step 3: Determine the change in concentration due to the addition of 0.200 mol of HI. Calculate the new concentration of HI by adding the moles of HI added to the initial moles and dividing by the volume of the vessel.
Step 4: Use the reaction quotient \( Q_c \) to determine the direction in which the reaction will shift to reestablish equilibrium. Compare \( Q_c \) with the equilibrium constant \( K_c \) calculated from the initial concentrations.
Step 5: Set up an ICE (Initial, Change, Equilibrium) table to calculate the changes in concentration for each species as the system returns to equilibrium. Use the stoichiometry of the balanced equation to express changes in terms of a single variable, and solve for the equilibrium concentrations.
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Consider the hypothetical reaction A(𝑔) + 2β€Šβ€ŠB(𝑔) β‡Œ 2 C(𝑔), for which 𝐾𝑐 = 0.25 at a certain temperature. A 1.00-L reaction vessel is loaded with 1.00 mol of compound C, which is allowed to reach equilibrium. Let the variable x represent the number of mol/L of compound A present at equilibrium. (e) From the plot in part (d), estimate the equilibrium concentrations of A, B, and C. (Hint: You can check the accuracy of your answer by substituting these concentrations into the equilibrium expression.)

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At a temperature of 700 K, the forward and reverse rate constants for the reaction 2 HI(𝑔) β‡Œ H2(𝑔) + I2(𝑔) are π‘˜π‘“=1.8Γ—10βˆ’3 π‘€βˆ’1sβˆ’1 and π‘˜π‘Ÿ = 0.063β€Šβ€Šπ‘€βˆ’1sβˆ’1. (b) Is the forward reaction endothermic or exothermic if the rate constants for the same reaction have values of π‘˜π‘“ = 0.097β€Šπ‘€βˆ’1sβˆ’1 and π‘˜π‘Ÿ = 2.6 π‘€βˆ’1sβˆ’1 at 800 K?

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