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Ch.15 - Chemical Equilibrium
All textbooksMcMurry 8th EditionCh.15 - Chemical EquilibriumProblem 84
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Chapter 15, Problem 84

Calculate the equilibrium concentrations of N2O4 and NO2 at 25 °C in a vessel that contains an initial N2O4 concentration of 0.0500 M. The equilibrium constant Kc for the reaction N2O4(g) ⇌ 2 NO2(g) is 4.64 × 10⁻³ at 25 °C.

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Step 1: Write the balanced chemical equation for the reaction: \( \text{N}_2\text{O}_4(g) \rightleftharpoons 2 \text{NO}_2(g) \).
Step 2: Set up an ICE (Initial, Change, Equilibrium) table to track the concentrations of \( \text{N}_2\text{O}_4 \) and \( \text{NO}_2 \) at each stage. Initially, \( [\text{N}_2\text{O}_4] = 0.0500 \text{ M} \) and \( [\text{NO}_2] = 0 \text{ M} \).
Step 3: Define the change in concentration for \( \text{N}_2\text{O}_4 \) as \( -x \) and for \( \text{NO}_2 \) as \( +2x \), where \( x \) is the amount of \( \text{N}_2\text{O}_4 \) that dissociates.
Step 4: Express the equilibrium concentrations in terms of \( x \): \( [\text{N}_2\text{O}_4] = 0.0500 - x \) and \( [\text{NO}_2] = 2x \).
Step 5: Substitute these expressions into the equilibrium constant expression \( K_c = \frac{[\text{NO}_2]^2}{[\text{N}_2\text{O}_4]} \) and solve for \( x \) to find the equilibrium concentrations.
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Textbook Question
The value of Kc for the reaction 3 O21g2 ∆ 2 O31g2 is 1.7 * 10-56 at 25°C. Do you expect pure air at 25 °C to contain much O3 (ozone) when O2 and O3 are in equilib- rium? If the equilibrium concentration of O2 in air at 25 °C is 8 * 10-3 M, what is the equilibrium concentration of O3?
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Open Question
Phosphine (PH3) decomposes at elevated temperatures, yielding gaseous P2 and H2: 2 PH3(g) ⇌ P2(g) + 3 H2(g), Kp = 398 at 873 K. (b) When a mixture of PH3, P2, and H2 comes to equilibrium at 873 K, P_P2 = 0.412 atm and P_H2 = 0.822 atm. What is P_PH3?
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At 500 K, the equilibrium constant for the dissociation reaction H2(g) ⇌ 2H(g) is very small (Kc = 1.2 × 10⁻⁴²). (a) What is the molar concentration of H atoms at equilibrium if the equilibrium concentration of H2 is 0.10 M? (b) How many H atoms and H2 molecules are present in 1.0 L of 0.10 M H2 at 500 K?
Textbook Question
Calculate the equilibrium concentrations at 25 °C for the reaction in Problem 15.84 if the initial concentrations are 3N2O44 = 0.0200 M and 3NO24 = 0.0300 M.
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Open Question
A sample of HI 19.30 * 10^-3 mol^2 was placed in an empty 2.00-L container at 1000 K. After equilibrium was reached, the concentration of I2 was 6.29 * 10^-4 M. Calculate the value of Kc at 1000 K for the reaction H2(g) + I2(g) ⇌ 2 HI(g).
Textbook Question
The industrial solvent ethyl acetate is produced by the reac-tion of acetic acid with ethanol: CH3CO2H1soln2 + CH3CH2OH1soln2 ∆ CH3CO2CH2CH31soln2 + H2O1soln2 Ethyl acetate (b) A solution prepared by mixing 1.00 mol of acetic acid and 1.00 mol of ethanol contains 0.65 mol of ethyl ace- tate at equilibrium. Calculate the value of Kc. Explain why you can calculate K without knowing the volume of the solution.
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