Quiz 13 [PDF]

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Quiz 13 

Question 1 Consider a reaction for which Qc = 0.600 mol/L with calculated Kc = 0.987 mol/L. Which of the following statements about the equilibrium is correct? Answers: A. The reaction essentially does not occur B. The reaction moves from right to left to reach equilibrium C. The reaction essentially goes to completion D. The reaction moves from left to right to reach equilibrium

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Question 2 When writing equilibrium-constant expressions for chemical reactions involving a pure solid, the concentration of the pure solid is Answers: A. is treated as an aqueous solution B. represented by the density of the pure solid C. not included in the equilibrium constant expression D. determined by a series of volume and mass experiments

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Question 3 Suppose liquid water and water vapor exist in equilibrium in a closed container. If you add a small amount of liquid water to the container, how does this affect the amount of water vapor in the container? Answers:

A. The amount of water vapor in the container tends to increase. B. The amount of water vapor in the container does not change C. The amount of water vapor in the container tends to decrease. D. Not enough information to conclude.

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Question 4 Consider the reaction 2N2O(g) + 3O2(g) ↔ 2N2O4(g) Which is an endothermic reaction. What is the effect of increasing the concentration of N2O? Answers: A. there will be no effect B. [O2] will decrease

C. [N2O4] will decrease D. the reaction will be driven to the left 

Question 5 The following reaction has an equilibrium constant Kc equal to 3.59 at 900°C.

CH4(g) + 2H2S(g) ↔ CS2(g) +4H2(g) The composition is recorded as [CH4] = 1.26 M, [H2S] = 1.32 M, [CS2] = 1.43 M, [H2] = 1.12 M, identify direction the reaction should go to reach equilibrium. Answers: A. To the left B. Not enough information to identify direction C. At equilibrium D. To the right 

Question 6 Methanol, CH3OH, formerly known as wood alcohol, is manufactured commercially by the following reaction: CO(g) + 2H2(g) ↔ CH3OH(g). A 1.500-L vessel was filled with 0.1500 mol CO and 0.3000 mol H2. When this mixture came to equilibrium at 500 K, the vessel contained 0.1187 mol CO. What is the equilibrium constant of reaction (Kc)? Answers: A. 25.0 B. 4.68 C. 10.5 D. 1.67

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Question 7 You place 0.600 mol of nitrogen, N2, and 1.800 mol of hydrogen, H2, into a reaction vessel at 450°C and 10.0 atm. The reaction is N2(g) + 3H2(g) ↔ 2NH3(g). What is the composition of the equilibrium mixture if you obtain 0.048 mol of ammonia, NH3, from it? Answers: A. The final mixture includes 0.576 mol of N2, 1.782 mol of H2 and 0.048 mol of NH3 B. The final mixture includes 0.576 mol of N2, 1.728 mol of H2 and 0.048 mol of NH3 C. The final mixture includes 0.576 mol of N2, 1.287 mol of H2 and 0.048 mol of NH3 D. Inadequate information to solve

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Question 8 One way of preparing hydrogen is by the decomposition of water. What would you expect to be the effect of an increase of temperature of the following reaction? 2H2O(g) ↔ 2H2(g) + O2(g); ∆H°= 484 kJ I. The reaction is exothermic II. The reaction would shift to the right III. The amount of H2O(g) would decrease IV. Nothing would happen

Answers: A. i, ii, iii B. i, iv C. i, ii D. ii, iii 

Question 9 A mixture initially consisting of 2 mol CO and 2 mol H2 comes to equilibrium with methanol, CH3OH, as the product: CO(g) + 2H2(g) ↔ CH3OH(g). At equilibrium, the mixture will contain which of the following? Answers: A. 1 mol CH3OH B. more than 1 mol CH3OH but less than 2 mol C. less than 1 mol CH3OH D. 2 mol CH3OH

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Question 10 Consider the A ↔ B reaction for which Kc = 0.798 mol/L. Which of the following statements about the equilibrium is CORRECT? Answers: A. There are slightly more products than reactants in the mixture B. The reaction essentially goes to completion C. There are slightly more reactants than products in the mixture D. The rates of the forward and reverse reactions are not equal

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Question 11 If Keq = 8.13 for A + 2B ↔ 2C , then for 2C ↔ A + 2B , Keq = Answers: A. 13.9 B. 0.123 C. -8.13 D. 6.48

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Question 12 The amount of nitrogen dioxide formed by dissociation of dinitrogen tetroxide, N2O4(g) ↔ 2NO2(g), increases as the temperature rises. What can be concluded? Answers: A. The reaction equilibrium does not depend on temperature B. Nothing can be concluded C. The reaction is endothermic D. The reaction is exothermic

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Question 13

Which of the following correctly describes a relation between the equilibrium constant (K) and the equilibrium quotient (Q) so that the reaction can reach the equilibrium? Answers: A. Q = K: reaction shifts to reactants B. Q > K: reaction shifts to products C. Q > K: reaction shifts to reactants D. Q < K: equilibrium established 

Question 14 The following reaction has an equilibrium constant Kc equal to 3.07 x10-4 at 24°C. 2NOBr(g) ↔ 2NO(g) + Br2(g) For each of the following compositions, in which is the reaction mixture at equilibrium? Answers: A. [NOBr] = 0.121 M, [NO] = 0.0159 M, [Br2] = 0.0139 M B. [NOBr] = 0.0472 M, [NO] = 0.0121 M, [Br2] = 0.0105 M C. [NOBr] = 0.103 M, [NO] =0.0134 M, [Br2] = 0.0181 M D. [NOBr] = 0.0720 M, [NO] = 0.0162 M, [Br2] = 0.0123 M

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Question 15 Consider the following reactions at 1200 K and find value of K3 (Reaction 1): CO(g) + 3H2(g) ↔ CH4(g) + H2O(g); K1= 3.92 (Reaction 2): CH4(g) + 2H2S(g) ↔ CS2(g) + 4H2(g); K2=3.3 x 104 (Reaction 3): CO(g) + 2H2S(g) ↔ CS2(g) + H2O(g) + H2(g); K3 Answers: A. 1.29x103 B. 12.9x104 C. 129x101 D. None of the above

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Question 16 The value of Kc for the following reaction at 900°C is 0.28. CS2(g) + 4H2(g) ↔ CH4(g) + 2H2S(g). What is Kp at this temperature? Answers: A. 2.9 x 10-5 B. 2.7 x 10-5 C. 3.4 x 10-5 D. 3.0 x 10-5

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Question 17 When a system has reached equilibrium, it means that

Answers: A. The forward rate is faster than the reverse rate. B. The chemical reaction goes to completion and there is no reverse rate. C. The forward and reverse rates of the chemical reaction are equal. D. The forward rate is slower than the reverse rate. 

Question 18 Q. 1. An equilibrium mixture for the reaction N2(g) + 3H2(g) ↔ 2NH3(g) has the following concentrations: [N2] = 0.075 mol/L, [H2] = 0.150 mol/L, and [NH3] = 0.0550 mol/L. What is the equilibrium constant, Keq? Answers: A. 0.01100 B. 11.95 C. 71.10 D. 0.01410

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Question 19 For which of the following equilibria is Kc = Kp Answers: A. 2H2(g) + O2(g) ↔ 2H2O(g) B. CH4(g) + H2O(g) ↔ CO(g) + 3H2(g) C. C(s) + CO2(g) ↔ 2CO(g) D. N2(g) + O2(g) ↔ 2NO(g)

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Question 20 Consider the equilibrium: FeO(s) + CO(g) ↔ Fe(s) + CO2(g). How to increase the quantity of products in this equilibrium? I. Add more FeO II. Add more CO2 III. Remove Fe IV. Remove CO2 Answers: A. All off the above B. ii, iii, iv C. i, iii, iv D. i, ii, iv