1) If sulfuric acid is added to the system, the color changes from _______ to ________. a) yellow; orange b) orange; yellow c) colorless; yellow d) yellow; colorless e) colorless; orange f) orange; colorless 2) When the color changes from yellow to orange, this indicates that the concentration of ____ ions increased while the concentration of ____ ions decreased. a) CrO4- ; H+ b) Cr2O72- ; H+ c) CrO42- ; Cr2O72- d) H+ ; Cr2O72- e) Cr2O72- ; CrO42- f) H+ ; CrO4- 3) As the concentration of Cr2O72- increases, what happens to equilibrium? a) Equilibrium shifts right, favoring formation of products.  b) Equilibrium shifts left, favoring formation of products. c) Equilibrium shifts right, favoring formation of reactants. d) Equilibrium shifts left, favoring formation of reactants. 4) A(n) __________ reaction is one that takes place in both the forward & reverse directions.  a) irreversible b) product favored c) reactant favored d) reversible 5) When Q>K, a net __________ reaction will occur until equilibrium is reached. a) forward b) reverse 6) When K=Q, the reaction... a) proceeds in the reverse direction.  b) proceeds in the forward direction.  c) stops. d) proceeds equally in the forward and reverse directions until equilibrium is reached. 7) In a dynamic equilibrium, the rate of forward & reverse reactions are equal. a) True b) False c) Cannot be determined 8) For equilibrium to be established, a closed system is needed. a) True b) False c) Cannot be determined 9) At equilibrium, the concentrations of reactants and products became equal. a) True b) False c) Cannot be determined 10) When Kc is very large, the products are favored. a) True b) False c) Cannot be determined 11) While holding temperature constant, increasing the concentration of a reactant in an equilibrium system will cause Kc to increase.  a) True b) False c) Cannot be determined 12) Decreasing temperature causes K for an endothermic reaction to increase. a) True b) False c) Cannot be determined 13) A saturated salt solution is an example of a equilibrium system. a) True b) False c) Cannot be determined 14) Addition of a catalyst will increase the percent yield in a chemical reaction. a) True b) False c) Cannot be determined 15) When writing an equilibrium expression, solids and liquids are omitted because their concentration remains constant. a) True b) False c) Cannot be determined 16) Some SO3 is put into an evacuated flask. How do the rates of the forward & reverse rates change as the system approaches equilibrium?  a) increases; increases b) increases; decreases c) decreases; increases d) decreases; decreases 17) A chemist placed some ammonia into an empty 2.0 L flask and found 0.060 mol N2 in the flask when equilibrium was reached. What was the concentration of H2 in the flask at equilibrium?  a) 0.010 M b) 0.020 M c) 0.090 M d) 0.18 M 18) For which of the following reaction systems would Kc = [O2]? a) b) c) d) 19) The reaction occurs in a closed 2.50 L vessel. The vessel was analyzed after equilibrium was established and 2.83 mol NO, 3.00 mol O2, and 18.0 mol NO2 were present. Calculate the equilibrium constant for the reaction.  a) 0.218 b) 1.83 c) 13.4 d) 33.8 20) At room temperature, the reaction N2O4(g) ⇌ 2NO2(g) has K = 0.0045. What is the K for the following reaction at the same temperature? NO2(g)<--->1/2 N2O4(g) a) 220 b) 15 c) 0.067 d) 0.0045 21) The value of the equilibrium constant for a gaseous reaction will change when... a) the temperature changes. b) a catalyst is added. c) the initial concentrations change. d) the volume of the flask changes. 22) H2(g) + I2(g) ⇌ 2HI(g) Which of the following graphs shows what happens when some HI is removed and a new equilibrium is established?  a) b) c) d) 23) N2(g) + O2(g) ⇌ 2NO(g) This reaction occurs at constant temperature. Based on the graph, which of the following occurred at time t.  a) N2 was added to the flask & the system shifted forward b) N2 was added to the flask & the system shifted backwards c) The system was transferred to a smaller flask & a forward shift occurred.  d) The system was transferred to a smaller flask & a reverse shift occurred. 24) N2(g) + 3H2(g) ⇌ 2NH3(g) (∆H<0) The system reaches equilibrium with all three gases present inside a sealed syringe with a movable plunger. Select all options that would result in a greater yield of ammonia.  a) add more N2(g) to the syringe b) remove N2(g) from the syringe c) push plunger in, reduce volume d) heat system e) cool system f) pull plunger out, increase volume 25) Calculate the value of Kc for the reaction: 2 NO(g) + Br2(g) ⇌ 2 NOBr (g) using the following information. a) 5x1056 b) 2x103 c) 2x10-57 26) A chemist was studying the reaction: 2BrI(g) ⇌ Br2(g) + I2(g) & determined that K=4. Calculate K for the reaction shown.  a) 4 b) 2 c) 1 d) 0.5 e) 0.25 f) 0.16 27) For the reaction 2CO(g) ⇌ C(s) + CO2(g), Keq = 7.7 x 10-15. At a particular time, the following concentrations are measured: [CO]=0.034 M, [CO2] =3.6x10-17 M. Is this reaction at equilibrium? If not which direction will the reaction proceed? a) Yes, the reaction is at equilibrium.  b) No; the reaction will proceed to the right, favoring the formation of products.  c) No; the reaction will proceed to the left, favoring the formation of products. d) No; the reaction will proceed to the right, favoring the formation of reactants.  e) No; the reaction will proceed to the left, favoring the formation of reactants.  28) For the reaction N2O4(g) ⇌ 2NO2(g), Keq = 0.2. Are the products or reactants favored?  a) products are slightly favored b) products are greatly favored c) reactants are slightly favored d) reactants are greatly favored e) The reaction is at equilibrium 29) For the reaction N2O4(g) ⇌ 2NO2(g), Keq = 0.02. At a particular time, the following concentrations are measured: [N2O4]=2.0 M, [NO2] = 0.2 M. Is this reaction at equilibrium? If not which direction will the reaction proceed? a) Yes, the reaction is at equilibrium. b) No; the reaction will proceed to the right, favoring the formation of products. c) No; the reaction will proceed to the left, favoring the formation of products. d) No; the reaction will proceed to the right, favoring the formation of reactants. e) No; the reaction will proceed to the left, favoring the formation of reactants.

Equilibrium Review

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