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Ch.15 - Chemical Equilibrium
McMurry - Chemistry 8th Edition
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모든 교과서McMurry 8th EditionCh.15 - Chemical Equilibrium문제 11
15장, 문제 11

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

검증된 단계별 안내
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Step 1: Write the balanced chemical equation for the decomposition of phosphorus pentachloride: \( \text{PCl}_5(g) \rightleftharpoons \text{PCl}_3(g) + \text{Cl}_2(g) \).
Step 2: Set up an ICE (Initial, Change, Equilibrium) table to track the concentrations of each species. Initially, [PCl5] = 0.250 M, and [PCl3] = [Cl2] = 0 M.
Step 3: Define the change in concentration for the reaction. Let \( x \) be the amount of PCl5 that decomposes. Then, the changes are: \([-x]\) for PCl5, \([+x]\) for PCl3, and \([+x]\) for Cl2.
Step 4: Express the equilibrium concentrations in terms of \( x \): [PCl5] = 0.250 - x, [PCl3] = x, and [Cl2] = x.
Step 5: Use the equilibrium constant expression \( K_c = \frac{[\text{PCl}_3][\text{Cl}_2]}{[\text{PCl}_5]} \) and substitute the equilibrium concentrations to solve for \( x \). Set \( K_c = 1.80 \) and solve the equation to find the value of \( x \).

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Chemical Equilibrium

Chemical equilibrium occurs when the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. In this case, the decomposition of phosphorus pentachloride (PCl5) into phosphorus trichloride (PCl3) and chlorine (Cl2) reaches a state where the concentrations no longer change over time, despite the ongoing reactions.
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가이드 코스
04:21
Chemical Equilibrium Concepts

Equilibrium Constant (Kc)

The equilibrium constant (Kc) is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium, each raised to the power of their coefficients in the balanced equation. For the reaction PCl5 ⇌ PCl3 + Cl2, Kc = [PCl3][Cl2]/[PCl5]. A Kc value greater than 1 indicates that products are favored at equilibrium, while a value less than 1 suggests that reactants are favored.
추천 영상:
가이드 코스
03:20
Equilibrium Constant Expressions

ICE Table (Initial, Change, Equilibrium)

An ICE table is a tool used to organize the initial concentrations, the changes in concentrations as the reaction proceeds, and the equilibrium concentrations of reactants and products. By setting up an ICE table for the given reaction, one can systematically determine how the initial concentration of PCl5 affects the equilibrium concentrations of PCl3 and Cl2, allowing for the calculation of the final concentrations based on the equilibrium constant.
추천 영상:
가이드 코스
01:14
ICE Charts and Equilibrium Amount
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교과서 질문

Calculate the value of the equilibrium constant at 427 °C for the reaction

Na O1s2 + 1>2 O 1g2 ∆ Na O 1s2

given the following equilibrium constants at 427 °C.

Na2O1s2 ∆ 2 Na1l2 + 1>2 O21g2 Kc = 2 * 10-25 Na O 1s2 ∆ 2 Na1l2 + O 1g2 K = 5 * 10-29

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교과서 질문
For the general, single-step reaction A1g2 + B1g2 ∆ AB1g2, Kc = 4.5 * 10-6, which of the following statements is true? (LO 15.16) (a) Ea 1forward2 6 Ea 1reverse2 (b) The equilibrium mixture contains mostly products. (c) kr 7 kf (d) The reaction is exothermic.
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