16. Chemical Equilibrium

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Multiple Choice

Which of the reactions is likely to produce more O₂ at equilibrium at 25°C?

204

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Multiple Choice

Consider the reaction A(g) ⇌ B(g) + C(g), with k_forward of 5.7 x 10^–2 and k_reverse of 3.8 x 10^–4. Which would be greater at equilibrium, partial pressure of A or partial pressures of B and C?

196

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Consider a reaction A21g2 + B21g2Δ2 AB1g2, with atoms of A shown in red in the diagram and atoms of B shown in blue.

(a) If Kc = 1, which box represents the system at equilibrium?

220

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.

214

The equilibrium constant for the dissociation of molecular iodine, I21g2Δ2 I1g2, at 800 K is Kc = 3.1 * 10-5. (b) Assuming both forward and reverse reactions are elementary processes, which reaction has the larger rate constant, the forward or the reverse reaction?

1065

Write the expression for Kc for the following reactions. In each case indicate whether the reaction is homogeneous or heterogeneous. (e) 2 Ag1s2 + Zn2+1aq2 Δ 2 Ag+1aq2 + Zn1s2

494

Write the expressions for Kc for the following reactions. In each case indicate whether the reaction is homogeneous or heterogeneous. (g) 2 C8H181l2 + 25 O21g2 Δ 16 CO21g2 + 18 H2O1l2

404

Write the expressions for Kc for the following reactions. In each case indicate whether the reaction is homogeneous or heterogeneous. (b) Ti1s2 + 2 Cl21g2 Δ TiCl41l2

360

Which of the following reactions lies to the right, favoring the formation of products, and which lies to the left, favoring formation of reactants? (b) 2 HBr1g2 Δ H21g2 + Br21g2 Kc = 5.8 * 10-18

492

Which of the following statements are true and which are false? (c) As the value of the equilibrium constant increases, the speed at which a reaction reaches equilibrium increases.

916

Write an expression for the equilibrium constant of each chemical equation. a. SbCl5(g) ∆ SbCl3(g) + Cl2(g)

830

Find and fix each mistake in the equilibrium constant expressions. b. CO(g) + Cl2(g) ⇌ COCl2(g) K = [CO][Cl2]/[COCl2]

347

Find and fix each mistake in the equilibrium constant expressions. a. 2 H2S(g) ⇌ 2 H2(g) + S2(g) K = [H2][S2]/[H2S]

416

When this reaction comes to equilibrium, will the concentra- tions of the reactants or products be greater? Does the answer to this question depend on the initial concentrations of the reac- tants and products? A(g)+B(g) ⇌ 2C(g) Kc = 1.4x10^-5

1362

A chemist trying to synthesize a particular compound attempts two different synthesis reactions. The equilibrium constants for the two reactions are 23.3 and 2.2 * 104 at room temperature. However, upon carrying out both reactions for 15 minutes, the chemist finds that the reaction with the smaller equilibrium constant produces more of the desired product. Explain how this might be possible.

1069

For each of the following equilibria, write the equilibrium constant expression for Kc. Where appropriate, also write the equilibrium constant expression for Kp. (a) Fe2O31s2 + 3 CO1g2 ∆ 2 Fe1l2 + 3 CO21g2

386

Which of the following reactions yield appreciable equilib- rium concentrations of both reactants and products? (a) 2 Cu1s2 + O21g2 ∆ 2 CuO1s2; Kc = 4 * 1045

490

In Section 11.5, we defined the vapor pressure of a liquid in terms of an equilibrium. (a) Write the equation representing the equilibrium between liquid water and water vapor and the corresponding expression for Kp.

449

For the reaction A2 + 2B ∆ 2 AB, the rate of the for- ward reaction is 18 M/s and the rate of the reverse reaction is 12 M/s. The reaction is not at equilibrium. Will the reaction pro- ceed in the forward or reverse direction to attain equilibrium?

667

Consider a general, single-step reaction of the type A + B ∆ C. Show that the equilibrium constant is equal to the ratio of the rate constants for the forward and reverse reactions, Kc = kf>kr.

440

Which of the following relative values of kf and kr results in an equilibrium mixture that contains large amounts of reactants and small amounts of products? (a) kf 7 kr (b) kf = kr (c) kf 6 kr

909

Refining petroleum involves cracking large hydrocar- bon molecules into smaller, more volatile pieces. A simple example of hydrocarbon cracking is the gas-phase thermal decomposition of butane to give ethane and ethylene: (a) Write the equilibrium constant expressions for Kp and Kc.

244

Open Question

What can be said about the relative amounts of reactants and products when K is approximately 1?

Open Question

When glucose, a sugar, reacts fully with oxygen, carbon dioxide and water are produced according to the equation: C₆H₁₂O₆(s) + 6 O₂(g) ⟺ 6 CO₂(g) + 6

H₂O(l) Write the expression for Kc for this reaction.

Open Question

For a particular reaction K = 98000. What can be said about this reaction?