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1 | |
Which of the following statements about the equilibrium shown is always true?
N2O4(g) ↔ 2NO2(g) |
| | A) | At equilibrium, [N2O4] = [NO2]2 |
| | B) | At equilibrium, kf[N2O4] = kr[NO2] |
| | C) | At equilibrium, [N2O4] = 2[NO2] |
| | D) | At equilibrium, kf[N2O4] = kr[NO2]2 |
| | E) | None of the above statements is necessarily true. |
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2 | |
What is the correct equilibrium constant expression for the following reaction?
2NO2(g) ↔ 2NO(g) + O2(g) |
| | A) | Kc = [O2]2[NO]/[NO2]2 |
| | B) | Kc = [O2][NO]2/[2NO2]2 |
| | C) | Kc = [NO2]2/[NO]2[O2] |
| | D) | Kc = [NO2]2/[NO][O2]2 |
| | E) | None of the above |
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3 | |
Consider the two equilibria and their equilibrium constants:
(1) 2NO2(g) ↔ N2O4(g) KC1
(2) ½N2O4(g) ↔ NO2(g) KC2
What, if any, is the relationship between Kc1 and Kc2? |
| | A) | Kc1 = Kc2 |
| | B) | Kc1 = 1/Kc2 |
| | C) | Kc1 = 2/Kc2 |
| | D) | Kc1 = 1/(Kc2)2 |
| | E) | No such general relationship exists. |
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4 | |
Consider the equilibrium reaction:
H2(g) + Cl2 ↔ 2HCl(g)
Which of the following correctly describes the relationship between Kc and Kp for the reaction? |
| | A) | Kp = Kc |
| | B) | Kp = (RT)Kc |
| | C) | Kp = (RT)2Kc |
| | D) | Kp = Kc/RT |
| | E) | Kp = Kc/(RT)2
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5 | |
Consider the equilibrium reaction:
3CIO-(aq) ↔ CIO3-(aq) + 2CI-(aq)
The equilibrium constant Kc = 3.2 X
103. The following concentrations are present: [Cl-] = 0.50 mol/L; [ClO3-] = 0.32 mol/L; [ClO-] = 0.24 mol/L. Is the mixture at equilibrium and, if not, in which direction will reaction proceed? |
| | A) | The system is at equilibrium. |
| | B) | The system is not at equilibrium; reaction will proceed left to right. |
| | C) | The system is not at equilibrium; reaction will proceed right to left. |
| | D) | The system cannot reach equilibrium since the ClO3- and Cl- concentrations are not in the stoichiometric ratio. |
| | E) | There is not enough information to tell. |
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6 | |
H2(g) + I2(g) ↔ 2HI(g)
For the equilibrium above, Kc = 12.3. If a reaction mixture has [H2] = [I2] = [HI] = 3.21 X
10-3 mol/L, which one of the following statements is true? |
| | A) | The concentration of HI will decrease as the system approaches equilibrium. |
| | B) | The system is at equilibrium. |
| | C) | The concentrations of H2 and I2 will increase as the system approaches equilibrium. |
| | D) | The concentrations of H2 and I2 will decrease as the system approaches equilibrium. |
| | E) | The system cannot reach equilibrium from the given starting conditions. |
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7 | |
Consider the reaction:
CH3Cl(aq) + OH-(aq) ↔ CH3OH(aq) + Cl-(aq)
When the reaction is started with 0.10 moles of CH3Cl and 0.20 moles of OH-, 0.030 moles of CH3OH are obtained at equilibrium. Calculate the equilibrium constant. |
| | A) | 0.18 |
| | B) | 0.076 |
| | C) | 0.0009 |
| | D) | 0.03 |
| | E) | 2.5 |
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8 | |
At elevated temperatures, solid silicon reacts with chlorine gas to form gaseous SiCl4:
Si(s) + 2Cl2(g) ↔ SiCl4(g)
When the reaction is started with 0.10 moles of Si and 0.20 moles of Cl2 in a one liter flask, 0.050 moles of SiCl4 are obtained at equilibrium. Calculate the equilibrium constant, Kc. |
| | A) | 0.10 |
| | B) | 1.0 |
| | C) | 2.0 |
| | D) | 5.0 |
| | E) | none of the above |
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9 | |
Consider the following gas-phase equilibrium:
H2(g) + I2(g) ↔ 2HI(g)
At a certain temperature, the equilibrium constant Kc is 4.0. Starting with equimolar quantities of H2 and I2 and no HI, when equilibrium was established, 0.20 moles of HI was present. How much H2 was used to start the reaction? |
| | A) | 0.10 mol |
| | B) | 0.23 mol |
| | C) | 0.20 mol |
| | D) | 4.0 mol |
| | E) | Need to know the volume of the reaction vessel. |
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10 | |
At a certain temperature the equilibrium constant Kp = 0.132 for the reaction:
PCl5(g) ↔ PCl3(g) + Cl2(g)
At equilibrium, the partial pressures of both PCl5 and PCl3 are 100. mmHg. What is the total pressure of the equilibrium system, in mmHg? |
| | A) | 100. mmHg |
| | B) | 200. mmHg |
| | C) | 300. mmHg |
| | D) | 400. mmHg |
| | E) | 332 mmHg |
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11 | |
Ammonium iodide dissociates reversibly to ammonia and hydrogen iodide:
NH4I(s) ↔ NH3(g) + HI(g)
At 400ºC, Kp = 0.215. If 150 g of ammonium iodide is placed into a 3.00-L vessel and heated to 400º
C, calculate the partial pressure of ammonia when equilibrium is reached. |
| | A) | 0.22 atm |
| | B) | 0.46 atm |
| | C) | 0.11 atm |
| | D) | 0.88 atm |
| | E) | 1.2 atm |
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12 | |
Calcium carbonate decomposes at high temperatures to calcium oxide and carbon dioxide:
CaCO3(s) ↔ CaO(s) + CO2(g)
Which of the following statements about this equilibrium is correct? |
| | A) | Adding more CaCO3 to the system at equilibrium will produce more CO2. |
| | B) | Adding more CaO to the system at equilibrium will produce more CaCO3. |
| | C) | Adding more CO2 to the system at equilibrium will produce more CaCO3. |
| | D) | A decrease in pressure will produce more CaCO3. |
| | E) | None of the above actions will affect the equilibrium position. |
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13 | |
Consider the equilibrium:
2NH3(g) ↔ N2(g) + 3H2(g) ΔH°rxn = 92 kJ
Which of the following actions will cause a shift to the left (in favor of reactants)? |
| | A) | removal of some H2 |
| | B) | addition of more NH3 |
| | C) | addition of gaseous Ar to increase the pressure in the vessel |
| | D) | increasing the volume of the container |
| | E) | lowering the temperature |
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14 | |
Consider the following reaction in the gas phase:
H2 + I2 ↔ 2HI
If the pressure increased by reducing the the volume of the flask, |
| | A) | more HI will be produced. |
| | B) | more H2 and I2 will be produced. |
| | C) | the results will depend on what the amounts of each are. |
| | D) | the amount of HI will remain the same. |
| | E) | the equilibrium constant will change. |
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15 | |
Consider the chemical equilibrium:
2SO2(g) + O2(g) ↔ 2SO3(g) ΔH°rxn = -196 kJ
An increase in temperature of the system will |
| | A) | cause the concentrations of both SO2 and SO3 to increase. |
| | B) | cause the concentration of SO3 to increase. |
| | C) | cause the equilibrium constant for the reaction to become larger. |
| | D) | cause the concentration of SO2 to increase. |
| | E) | not affect the position of the equilibrium. |
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