AP Chem - Unit 7 Exam
BaCO₃ (s) ⇋ Ba²⁺ (aq) + CO₃²⁻ (aq) | Ksp = 8.1 x 10⁻⁹ The dissolution of BaCO₃ (s) in water is represented above. A 20.0 mL sample of 1 x 10⁻⁴ M Ba(NO₃)₂ (aq) is mixed with an 80.0 mL sample of 1.0 x 10⁻⁴ M Na₂CO₃ (aq). Which of the following correctly predicts and explains the outcome?
A precipitate will not form, because Q = 1.6 x 10⁻⁹.
CaF₂ (s) ⇋ Ca²⁺ (aq) + 2F- (aq) | Ksp = 3.9 x 10⁻¹¹ HF (aq) ⇋ H+ (aq) + F- (aq) | Kc = 6.8 x 10⁻⁴ The dissolution of calcium fluoride is represented by the equilibrium system above at 25°C. The F- ion is produced when the weak acid HF dissociates. If solid calcium fluoride is added to equal volumes of the following solutions at 25°C, in which solution will the most calcium fluoride dissolve?
1 M HNO₃ (aq)
2S (s) + 2O₂ (g) ⇋ 2SO₂ (g) | K₁ = 2 x 10¹⁰⁵ 2SO₂ (g) + O₂ (g) ⇋ 2SO₃ (g) | K₂ = 7 x 10²⁴ Given the value of the equilibrium constants K₁ and K₂ for the reactions represented above, what is the value of the equilibrium constant, K₃, for the following reaction? 2S (s) + 3O₂ (g) ⇋ 2SO₃ (g) | K₃ = ?
1 x 10¹³⁰
Ge (g) + 2Cl₂ (g) ⇋ GeCl₄ (g) The value of the equilibrium constant for the reaction represetned above is 1 x 10¹⁰. What is the value of the equilibrium constant for the following reaction? 2GeCl₄ (g) ⇋ 2Ge (g) + 4Cl₂ (g)
1 x 10⁻²⁰
N₂O₄ (g) ⇋ 2NO₂ (g) | Kp = 3.0 at 70∘C colorless brown A mixture of NO₂ (g) and N₂O₄(g) is placed in a glass tube and allowed to reach equilibrium at 70°C, as represented above. If PN₂O₄ is 0.64 atm when the system is at equilibrium at 70°C, what is PNO₂?
1.4 atm
N₂O₅ (g) ⇋ 2NO₂ (g) + 1/2O₂ (g) The equilibrium constant for the gas phase reaction above is 95 at 25∘C. What is the value of the equilibrium constant for the following reaction at 25∘C? O₂ (g) + 4NO₂ (g) ⇋ 2N₂O₅ (g)
1/(95)²
ICl (g) ⇋ 1/2I₂ (g) + 1/2Cl₂ (g) | Keq = 0.1 Based on the information above, what is the value of Keq for the reaction represented above? I₂ (g) + Cl₂ (g) ⇋ 2ICl (g)
100
2NO₂ (g) ⇋ N₂O₄ (g) A 0.0300 mol sample of NO₂ (g) is placed in a rigid 1.00 L reaction vessel and allowed to reach equilibrium at a certain temperature. What is the value of K꜀ at this temperature if 0.00500 mol of N₂O₄ (g) is present at equilibrium?
12.5
2X (g) + Y (g) ⇋ 3Z (g) The reaction mixture represented above is at equilibrium at 298 K, and the molar concentrations are [X] = 2.0 M, [Y] = 0.5 M, and [Z] = 4.0 M. What is the value of the equilibrium constant for the reaction at 298 K?
32
X (g) + Y(g) ⇋ 2Z (g) When 4.00 mol each of X (g) and Y (g) are placed in a 1.00 L vessel and allowed to react at constant temperature according to the equation above, 6.00 mol of Z (g) is produced. What is the value of the equilibrium constant, K꜀?
36
The value of Ksp for PbCl₂ is 1.6 x 10⁻⁵. What is the lowest concentration of Cl- (aq) that would be needed to begin precipitation of PbCl₂ (s) in 0.010 M Pb(NO₃)₂?
4.0 x 10⁻² M
In a saturated solution of Zn(OH)₂ at 25∘C , the value of [OH-] is 2.0 x 10⁻⁶ M. What is the value of the solubility-product constant, Ksp, for Zn(OH)₂ at 25∘C?
4.0 x 10⁻¹⁸
Ba(IO₃)₂ (s) ⇋ Ba²⁺ (aq) + 2IO₃- (aq) Ksp = 4 x 10⁻⁹ According to the information about the dissolution of Ba(IO₃)₂ (s) shown above, the correct value of S, the molar solubility of Ba(IO₃)₂ (s), can be calculated using which of the following mathematical relationships?
4S³ = 4 x 10⁻⁹ M
H₂ (g) + Br₂ (g) ⇋ 2HBr (g) At a certain temperature, the value of the equilibrium constant, K, for the reaction represented above is 2.0 x 10⁵. What is the value of K for the reverse reaction at the same temperature?
5.0 x 10⁻⁶
2NO₂ (g) ⇋ N₂O₄ (g) A 0.0688 mol sample of NO₂ (g) is placed in a rigid 1.00 L reaction vessel and allowed to reach equilibrium at a certain temperature. What is the value of K꜀ at this temperature if 0.0133 mol of N₂O₄ (g) is present at equilibrium?
7.47
Reaction 1: CaC₂ (s) + 2H₂O (l) → C₂H₂ (g) + Ca(OH)₂ (s) Reaction 2: NaOCl (aq) + 2HCl (aq) → Cl₂ (g) + NaCl (aq) + H₂O (l) Reaction 3: C₂H₂ (g) + Cl₂ (g) → C₂H₂Cl₂ (g) Ca(OH)₂ (s) precipitates when a 1.0 g sample of CaC₂ (s) is added to 1.0 L of distilled water at room temperature. If a 0.064 g sample of CaC₂ (s) (molar mass 64 g/mol) is used instead and all of it reacts, which of the following will occur and why? (The value of Ksp for Ca(OH)₂ is 8.0 x 10⁻⁸)
Ca(OH)₂ will not precipitate because Q < Ksp
What is the molar solubility in water of Ag₂CrO₄ ? (The Ksp for Ag₂CrO₄ is 8 x 10⁻¹²)
Cubic root of 2 x 10⁻¹² M
Mg(OH)₂ (s) ⇋ Mg²⁺ (aq) + 2OH- (aq) The exothermic dissolution of Mg(OH)₂ (s) in water is represented by the equation above. The Ksp of Mg(OH)₂ (s) is 1.8 x 10-11. Which of the following changes will increase the solubility of Mg(OH)₂ in an aqueous solution?
Decreasing the pH
A graph shows that as concentration of NaF (x-axis) increases, concentration of Ca²⁺ (y-axis) decreases. Which of the following statements best explains the trend in the molar solubility of CaF₂ (s) in various concentrations of NaF (aq) shown in the graph above?
Higher concentrations of F- (aq) allow less CaF₂ (s) to dissolve before the solution becomes saturated.
2H₂S (g) + CH₄ (g) ⇋ CS₂ (g) + 4H₂ (g) | K꜀ = 3.4 x 10⁻⁴ A 0.10 mol sample of each of the four species in the reaction represented above is injected into a rigid, previously evacuated 1.0 L container. Which of the following species will have the highest concentration when the system reaches equilibrium?
H₂S (g)
4HCl (g) + O₂ (g) ⇋ 2Cl₂ + 2H₂O (g) Equal numbers of moles of HCl and O₂ in a closed system are allowed to reach equilibrium as represented by the equation above. Which of the following must be true at equilibrium? I. [HCl] must be less than [Cl₂] II. [O₂] must be greater than [HCl] III. [Cl₂] must be equal [H₂O]
II and III only
High solubility of an ionic solid in water is favored by which of the following conditions? I. The existence of strong ionic attractions in the crystal lattice II. The formation of strong ion-dipole attractions III. An increase in entropy upon dissolving
II and III only
Fe³⁺ (aq) + SCN- (aq) ⇋ Fe(SCN)²⁺ (aq) For the reaction represented above, the value of the equilibrium constant, Keq, is 240 at 25∘C. From this information, correct deductions about the reaction at 25∘C include which of the following? I.) The reaction is quite rapid II.) The product is favored over the reactants at equilibrium III.) The reaction is endothermic
II only
Which of the following statements is true for the equilibrium vapor pressure of a liquid in a closed system?
It is independent of the volume of the vapor phase
La³⁺ + OH- + HCO₃- ⇋ LaCO₃⁺ + H₂O | K₁ HCO₃- ⇋ H⁺ + CO₃²⁻ | Kₐ H₂O ⇋ H⁺ + OH- | Kᵥᵥ Based on the information above, which of the following expressions represents the equilibrium constant, K, for the reaction represented by the equation above? La³⁺ + CO₃²⁻ ⇋ LaCO₃⁺
K = (K₁) (Kᵥᵥ) / (Kₐ)
CO (g) + 2H₂ (g) ⇋ CH₃OH (g) | △H<0 The synthesis of CH₃OH (g) from CO(g) and H₂ (g) is represented by the equation above. The value of Kc for the reaction at 483 K is 14.5. Which of the following explains the effect on the equilibrium constant, Kc, when the temperature of the reaction system is increased to 650 K?
Kc will decrease because the reaction is exothermic.
PCl₅ (g) ⇋ PCl₃ (g) + Cl₂ (g) PCl₅ (g) decomposes into PCl₃ (g) and Cl₂ (g) according to the equation above. A pure sample of PCl₅ (g) is placed in a rigid, evacuated 1.00 L container. The initial pressure of the PCl₅ (g) is 1.00 atm. The temperature is held constant until the PCl₅ (g) reaches equilibrium with its decomposition products. The figures below show the initial and equilibrium conditions of the system: Figure 1 - initial - PCl₅ Ptotal= 1.00 atm Figure 2 - equilibrium - PCl₅, PCl₃, Cl₂ Ptotal= 1.40 atm Which of the following statements about Kp, the equilibrium constant for the reaction, is correct?
Kp < 1
SO₂ (g) + 1/2O₂ (g) ⇋ SO₃ (g) | k1 2SO₃ (g) ⇋ 2SO₂ (g) + O₂ (g) | k2 Which of the following shows the relationship between K1 and K2 in the reactions represented above?
K₂ = 1/(K₁)²
Reaction 1: CO (g) + 3H₂ (g) ⇋ CH₄ (g) + H₂O (g) | K₁ = [CH₄][H₂O]/[CO][H₂]³ Reaction 2: CO₂ (g) + H₂ (g) ⇋ CO (g) + H₂O (g) | K₂ = [CO][H₂O]/[CO₂][H₂] Reaction 3: CH₄ (g) + 2H₂O (g) ⇋ CO₂ (g) + 4H₂ (g) | K₃ = ? The chemical equations and equilibrium expressions for two reactions at the same temperature are given above. Based on the information, which of the following expressions can be used to calculate the value of K₃ for reaction 3 at the same temperature?
K₃ = 1/K₁ x 1/K₂
CaCO₃ (s) ⇋ CaO (s) + CO₂ (g) | △H° = 178 kJ/molrxn The reaction system represented above is at equilibrium. Which of the following will decrease the amount of CaO(s) in the system?
Lowering the temperature of the system
CO (g) + 3H₂ (g) ⇋ CH₄ (g) + H₂O (g) | Kp= 66 at 500∘C At a certain time, the partial pressure of the gases in the reaction mixture represented above had the values shown in the table below. PCO = 0.02 atm PH₂ = 1.0 atm PCH₄ = 0.4 atm PH₂O = 0.4 atm Based on the information above, which of the following occurred as the reaction mixture moved toward equilibrium?
More CH₄ (g) was produced because the rate of the forward reaction was higher than the rate of the reverse reaction.
H₂ (g) + I₂ (g) ⇋ 2HI (g) At 450∘C, 2.0 moles of each of H₂, I₂, and HI are combined in a 1.0 L rigid container. The value of Kc at 450∘C is 50. Which of the following will occur as the system moves toward equilbrium?
More HI(g) will form.
Ag₂SO₄ | Ksp = 1 x 10⁻⁵ PbSO₄ | Ksp = 1 x 10⁻⁸ A 1.0 L solution AgNO₃ (aq) of and Pb(NO₃)₂ (aq) has a Ag+ concentration of 0.020 M and a Pb2+ concentration of 0.0010 M. A 0.0010 mol sample of K₂SO₄ (s) is added to the solution. Based on the information in the table above, which of the following will occur?
Only PbSO₄ (s) will precipitate
2HI (g) ⇋ H₂ (g) + I₂ (g) Kp = 0.0016 The decomposition of HI (g) at 298 K is represented by the equilibrium equation above. When 100. torr of HI (g) is added to a previously evacuated, rigid container and allowed to reach equilibrium, the partial pressure of I₂ (g) is approximately 3.7 torr. If the initial pressure of HI (g) is increased to 200. torr and the process is repeated at the same temperature, which of the following correctly predicts the equilibrium partial pressure of I₂ (g), and why?
PI₂ = 7.4 torr, because it is directly proportional to the initial pressure of HI
H₃PO₄ ⇋ H⁺ + H₂PO₄- | Ka = 7.2 x 10⁻³ H₂PO₄- ⇋ H⁺ + PO₄²⁻ | Ka = 6.3 x 10⁻⁸ HPO₄²⁻ ⇋ H⁺ + PO₄³⁻ | Ka = 4.5 x 10⁻¹³ A solution is prepared by mixing 50 mL of 1 M NaH₂PO₄ with 50 mL of 1 M H₂PO₄. On the basis of the information above, which of the following species is present in the solution at the lowest concentrations?
PO₄³⁻
Pb(OH)₂ (s) Ksp = 1.2 x 10⁻¹⁵ PbI₂ (s) Ksp = 1.4 x 10⁻⁸ PbF₂ (s) Ksp = 4.0 x 10⁻⁸ Equimolar samples of Pb(OH)₂ (s), PbI₂ (s) , and PbF₂ (s) are placed in three separate beakers, each containing 250 mL of water at 25°C. After the solutions are stirred, solid remains in the bottom of each beaker. Based on the Ksp values for the compounds listed in the table above, a solution of which of the compounds will have the lowest [Pb2+] ?
Pb(OH)₂ (s)
PbCl₂ Ksp = 1.2 x 10⁻⁵ CuCl Ksp = 1.6 x 10⁻⁷ AgCl Ksp = 1.8 x 10⁻¹⁰ Hg₂Cl₂ Ksp = 1.4 x 10⁻¹⁸ Based on the Ksp values in the table above, a saturated solution of which of the following compounds has the highest [Cl-]?
PbCl₂
PbS: 1.7 x 10⁻¹⁴ M PbCO₃: 2.7 x 10⁻⁷ M PbCrO₄: 5.5 x 10⁻⁷ M PbSO₄: 1.6 x 10⁻⁴ M Based on [Pb²⁺] in a saturated solutions of the compounds listed in the table above, which of the compounds has the smallest Ksp value?
PbS
Ph(OH)₂ | Ksp= 1.2 x 10⁻¹⁵ PbI₂ | Ksp= 1.4 x 10⁻⁸ PbF₂ | Ksp= 4.0 x 10⁻⁸ Equimolar samples of Ph(OH)₂ (s), PbI₂(s), and PbF₂(s) are placed in three separate beakers, each containing 250 mL of water at 25°C. After the solutions are stirred, solid remains in the bottom of each beaker. Based on the Ksp values for the compounds listed in the table above, a solution of which of the compounds will have the lowest [Pb2+] ?
Ph(OH)₂
2NO (g) + Br₂ (g) ⇋ 2NOBr (g) | Kp= (PNOBr)² / (PNO)²(PBr₂) = 28 NO initial partial pressure - 10. torr Br₂ initial partial pressure - 2.0 torr NOBr inirial partial pressure - 80. torr The system represented by the equation above is allowed to establish equilibrium. The initial pressures of the substances are given in the table. Which of the following explains what the system will do as it approaches equilibrium?
Q = (80.)² /(10.)²(2.0) > Kp, and equilibrium will be approached by consuming because the reverse reaction is faster than the forward reaction.
2NO (g) + Cl₂ (g) ⇋ 2NOCl (g) | K꜀ = 2000 A mixture of NO (g) and Cl₂ (g) is placed in a previously evacuated container and allowed to reach equilibrium according to the chemical equation shown above. When the system reaches equilibrium, the reactants and products have the concentrations listed in the following table. NO concentration (M) - 0.050 Cl₂ concentration (M) - 0.050 NOCl concentration (M) - 0.50 Which of the following is true if the volume of the container is decreased by one half?
Q = 1000, and the reaction will proceed toward products
Cl₂ (aq) + 2H₂O (l) ⇋ H₃O⁺ (aq) + Cl- (aq) + HOCl (aq) K꜀ = [H₃O⁺][Cl-][HOCl] / [Cl₂] = 4.8 x 10⁻⁴ The equilibrium reaction between Cl₂ (aq) and H₂O (l) at 25∘C is represented by the chemical equation shown above. If a solution at equilibrium at 25∘C is diluted with distilled water to twice its original volume, which of the following gives the value for Q꜀ and predicts the response by the system immediately after dilution?
Q꜀ = K꜀/4, and the rate of the forward reaction will be greater than the rate of the reverse reaction.
A cylinder with a moveable piston is completely filled with a small amount (100 millimoles) of liquid water at a pressure of 1.0atm and a temperature of 80∘C. All the air in the cylinder is excluded. The cylinder is placed in a water bath held at 80∘C. The piston is slowly moved out to expand the volume of the cylinder to 20L as the pressure inside the cylinder is monitored. A plot of the pressure versus volume for the system is shown in the figure above. Which of the following statements most closely indicates, with justification, the region of the curve where the equilibrium represented below occurs? H₂O (l) ⇋ H₂O (g) *Slope is zero at B and decreases from C onward*
Region B, because the pressure inside the cylinder is equal to the vapor pressure of water at 80 ∘C when both liquids and gas phases are present.
The process of dissolution of NaCl(s) in H₂O(l) is represented in the diagram above. Which of the following summarizes the signs of ∆H° and ∆S° for each part of the dissolution process? Breaking of solvent-solvent interactions: Breaking solute-solute interactions: Forming solute-solvent interactions:
Solvent-Solvent: △H°: + ∆S°: + Solute-Solute: △H°: + ∆S°: + Forming: △H°: - ∆S°: -
Fe³⁺ (aq) + SCN- (aq) ⇋ FeSCN²⁺ (aq) Colorless Colorless Red When colorless solutions containing Fe³⁺ (aq) ions and SCN- (aq) ions are combined, a deep-red complex ion, FeSCN²⁺ (aq) quickly forms, as shown in the net ionic equation above. Which of the following explains the observation that adding a few additional crystals KSCN (s) of results in the red color of the solution becoming deeper?
The added KSCN (s) dissolves, causing the reaction system to respond by producing more product to partially consume SCN- (aq) and reduce its concentration.
3O₂ (g) ⇋ 2O₃ (g) | K꜀ = 1.8 x 10⁻⁵⁶ at 570 K For the system represented above, [O₂] and [O₃ ] initially are 0.131 mol/L and 0.789 mol/L respectively. Which of the following best predicts what will occur as the system approaches equilibrium at 570 K?
The amount of O₃ (g) will decrease, because Q > Kc
Cr₂O₇²⁻ (aq) + 3H₂O (l) ⇋ 2CrO₄²⁻ (aq) + 2H₃O⁺ (aq) orange yellow The equilibrium system represented by the equation above initially contains equal concentrations of Cr₂O₇²⁻ (aq) and CrO₄²⁻ (aq). Which of the following statements correctly predicts the result of adding a sample of 6.0 M NaOH(aq) to the system, and provides an explanation?
The mixture will become more yellow because OH−(aq) will shift the equilibrium toward products.
Sn(OH)₂ | Ksp = 4S³ = 5.45 x 10⁻²⁷ CuCN | Ksp = S² = 3.47 x 10⁻²⁰ MgF₂ | Ksp= 4S³ = 5.16 x 10⁻¹¹ NiCO₃ | Ksp= S² = 1.42 x 10⁻⁷ The equilibrium constants for the dissolution of various substances in aqueous solution at 25∘C are listed in the table above. Which of the following provides a correct comparison of the molar solubilities of some of these substances based on their Ksp?
The molar solubilities for CuCN and NiCO₃ are calculated using S = (square root of Ksp) and CuCN has a lower molar solubility than NiCO₃
CdF₂ (s) ⇋ Cd²⁺ (aq) + 2F- (aq) A saturated aqueous solution of CdF₂ is prepared. The equilibrium in the solution is represented above. In the solution, [Cd²⁺] eq = 0.0585 M and [F-]eq = 0.117 M. Some 0.90 M NaF is added to the saturated solution. Which of the following identifies the molar solubility of CdF₂ in pure water and explains the effect that the addition of NaF has on this solubility?
The molar solubility of CdF₂ in pure water is 0.0585 M, and adding NaF decreases this solubility because the equilibrium shifts to favor the precipitation of some CdF₂.
As the number of moles of HCl added increases, the molar solubility of MgCO₃ increases MgCO₃ (s) ⇋ Mg²⁺ (aq) + CO₃²⁻ (aq) A saturated solution of MgCO₃ at equilibrium is represented by the equation above. Four different saturated solutions were prepared and kept at the same temperature. A given amount of HCl was added to each solution and data were collected to calculate the molar solubility of MgCO₃ as shown in the table above. Which of the following can be concluded from the data?
The molar solubility of MgCO₃ increases with increasing acidity (lower pH)
*Diagram shows 3 beakers after the addition of NH₄NO₃ compound to a beaker of water* At 298 K, NH₄NO₃ readily dissolves in water, suggesting that the change in free energy (△G ) favors the dissolution process. However, when NH₄NO₃ dissolves in water, the temperature of the water decreases. The particulate diagram above attempts to provide a microscopic view of the dissolution of NH₄NO₃ considering both the change in enthalpy (△H ) and the change in entropy (△S ). Which of the following explains what the particle diagram is able to illustrate and why?
The particle diagram is able to illustrate that entropy increases when NH₄NO₃ dissolves in water because the ions disperse in solution.
FeCO₃ (s) ⇋ Fe²⁺ (aq) + CO₃²⁻ (aq) Ksp = 3 x 10⁻¹¹ MnCO₃ (s) ⇋ Mn²⁺ (aq) + CO₃²⁻ | Ksp = 2 x 10⁻¹¹ Both reactions have a △H° of <0 and a △S°>0 The table above lists the equilibrium constants and changes in thermodynamic properties for the dissolution of FeCO₃ (s) and MnCO₃ (s) at 25 °C. The two particle diagrams below represent saturated solutions of each compound at equilibrium. Which of the following explains which of the properties listed in the table is best represented by the particle diagram? Diagram shows 6 moles of Fe²⁺ & 6 moles CO₃²⁻ Other diagram shows 5 moles Mn²⁺ and 5 moles CO₃²⁻
The particle diagrams best represent that the molar solubility is greater for FeCO₃ compared to MnCO₃ .
CuBr (s) ⇋ Cu+ (aq) + Br- (aq) Shown above is the chemical equation for the dissolution of the slightly soluble salt CuBr (s). Its Ksp value in pure water was experimentally determined. CuBr was found to be much less soluble in a 0.001 M NaBr solution than in pure water. Which of the following correctly explains the decrease in solubility of CuBr in 0.001 M NaBr?
The presence of additional Br- ions already in the solution means equilibrium will be reached when much less CuBr has dissolved.
PCl₃ (g) + Cl₂ (g) ⇋ PCl₅ (g) | K꜀ = 6.5 At a certain point in time, a 1.00 L rigid reaction vessel contains 1.5 mol of PCl₃ (g), 1.0 mol of Cl₂ (g), and 2.5 mol of PCl₅ (g) . Which of the following describes how the measured pressure in the reaction vessel will change and why it will change that way as the reaction system approaches equilibrium at constant temperature?
The pressure will decrease because Q < Kc.
X (g) + Y(g) ⇋ XY (g) In an experiment, X (g) and Y (g) were combined in a rigid container at constant temperature and allowed to react as shown in the equation above. The table provides the data collected during the experiment. 75 minutes: [X] - 8.0 x 10⁻³ and [XY] - 4.2 x 10⁻² 155 minutes on: [X] - 7.0 x 10⁻³ and [XY] - 4.3 x 10⁻²
The reaction reached equilibrium between 75 minutes and 155 minutes after the reactants were combined because the concentrations of X and XY remained constant.
2XY (g) ⇋ X₂ (g) + Y₂ (g) | Kp = 230 A certain gas, XY(g), decomposes as represented by the equation above. A sample of each of the three gases is put in a previously evacuated container. The initial partial pressures of the gases are shown in the table below. XY initial partial pressure - 0.010 atm X₂ initial partial pressure - 0.20 atm Y₂ initial partial pressure - 2.0 atm The temperature of the reaction mixture is held constant. In which direction will the reaction proceed?
The reaction will form more reactant
The figure above shows two closed containers (Container 1 is long and short, Container 2 is tall and skinny). Each contains the same volume of acetone in equilibrium which its vapor at the same temperature. The vapor pressure of the acetone is...
The same in both containers because the temperature because the temperature is the same.
AgCl (s) ⇋ Ag+ (aq) + Cl- (aq) | Ksp = 1.8 x 10⁻¹⁰ Shown above is information about the dissolution of AgCl (s) in water at 298 K. In a chemistry lab a student wants to determine the value of s, the molar solubility of AgCl, by measuring [Ag+] in a saturated solution prepared by mixing excess AgCl and distilled water. How would the results of the experiment be altered if the student mixed excess AgCl with tap water (in which [Cl-] = 0.010 M) instead of distilled water and the student did not account for the Cl- in the tap water?
The value obtained for Ksp would be too small because less AgCl (s) would dissolve because of the common ion effect due to the Cl- (aq) already in the water.
2A (g) + B(g) ⇋ 2C (g) A (g) and B (g) react to form C (g), according to the balanced equation above. In an experiment, a previously evacuated rigid vessel is charged with A (g), B (g), and C (g), each with a concentration of 0.0100 M. The following table shows the concentration of the gases at equilibrium at a particular temperature: [A] eq = 0.0180 [B] eq = 0.0140 [C] eq = 0.0020 If the experiment is repeated at a higher temperature at which K꜀ is larger, which of the following best describes the effect of the temperature change o the concentrations of the gases at equilibrium?
There will be a decrease in [A] eq that will be two times the decrease in [B] eq because A and B react in a 2-to-1 ratio.
Beaker X - 50 mL H₂O Beaker Y - 100 mL 1.0 M NaCl Beaker X contains 50 mL of distilled water and beaker Y contains 100 mL of 1.0 M NaCl. Solid AgCl is added to each of the beakers. After thoroughly stirring the contents of the beakers, some solid AgCl remains at the bottom of each beaker, as shown above. Which of the following is true?
[Ag+] is greater in beaker X.
Ag⁺ (aq) + 2NH₃ (aq) ⇋ [Ag(NH₃)₂]⁺ (aq) | K = 1 x 10⁷ Equal volumes of 0.1 M AgNO₃ (aq) and 0.4 M NH₃ are mixed and allowed to reach the equilibrium represented above. Which of the following correctly lists the equilibrium concentrations of the Ag⁺ (aq), NH₃ (aq), and [Ag(NH₃)₂]⁺ (aq) in order from least to greatest?
[Ag⁺]eq < [[ [Ag(NH₃)₂]⁺] eq < [NH₃] eq
Br₂ (g) + Cl₂ (g) ⇋ 2BrCl (g) | Keq = 10. N₂ (g) + O₂ (g) ⇋ 2NO (g) | Keq = 4.2 x 10⁻³¹ The table above shows data for the two reactions carried out in two separate evacuated 1.0-liter rigid containers at constant temperatures of 298 K. To each container a .50 mol of the appropriate reactants was added, and the reaction was allowed to reach equilibrium. Based on this information, which of the following correctly compares the relative concentrations of BrCl and NO present inside their respective container at equilibrium?
[BrCl]eq > [NO]eq because the much larger Keq for reaction 1 means that a much higher concentration of products will be present at equilibrium for reaction 1 compared to reaction 2.
CO (g) + H₂O (g) ⇋ CO₂ (g) + H₂ (g) | K꜀ = 1.5 x 10³ A 2.0 mol sample of CO (g) and a 2.0 mol sample of H₂O (g) are introduced into a previously evacuated 100. L rigid container, and the temperature is held constant as the reaction represented above reaches equilibrium. Which of the following is true at equilibrium?
[CO₂] > [CO]
CO (g) + 2H₂ (g) ⇋ CH₃OH (g) △H < 0 The synthesis of CH₃OH (g) from CO(g) and H₂ (g) is represented by the equation above. The value of Kc for the reaction at 483 K is 14.5. A 1.0 mol sample of CO(g) and a 1.0 mol sample of H₂ (g) are pumped into a rigid, previously evacuated 2.0 L reaction vessel at 483 K. Which of the following is true at equilibrium?
[H₂] < [CO]
At night, an equilibrium reaction between two different nitrogen compounds generates N₂O₅ in the atmosphere, as represented below. Reaction 1: NO₃(g)+NO₂(g) ⇄ N₂O₅(g) K=2.6×10⁻¹¹ A mixture of NO₃ and a ten-fold excess of NO₂ are placed inside a rigid container at constant temperature and allowed to reach equilibrium. Which of the following provides a correct comparison of the equilibrium concentrations of these chemical species, and why?
[N₂O₅] << [NO₂], because a small K value indicates that the formation of products is not favored at equilibrium.
X (g) + 2Q (g) ⇋ R (g) + Z (g) | K꜀ = 1.3 x 10⁵ at 50∘C A 1.0 mol of sample of X (g) and a 1.0 mol sample of Q (g) are introduced into an evacuated rigid 10.0 L container and allowed to reach equilibrium at 50∘C according to the equation above. At equilibrium, which of the following is true about the concentrations of the gases?
[R] = [Z] > [Q]
X₂ (g) + Y₂ (g) ⇋ 2XY (g) | K꜀ = 3.0 A mixture of X₂ (g), Y₂ (g), and XY (g) is placed in a previously evacuated, rigid container and allowed to reach equilibrium at a constant temperature, as shown above. Which of the following sets of initial concentrations would lead to the formation of more products as the system moves towards equilibrium?
[X₂]initial = 0.50 M [Y₂]initial = 0.45 M [XY]initial = 0.20 M
Initial concentration (M) of Y: 2.0 Initial concentration (M) of Z: 0.0 Equilibrium concentration (M) of Y: 1.2 Equilibrium concentration (M) of Z: 0.80 The diagram above represents the equilibrium between the two isomers of C₂H₂Cl₂, and the table provides the data collected in an experiment to determine its equilibrium constant, K꜀, at 490 K. In a second experiment done at the same temperature, [Z]eq = 1.0 M. Which of the following is the approximate equilibrium concentration of Y in the second experiment, and why?
[Y]eq = 1.5 M because the ratio [Z]eq / [Y]eq should remain constant when the reaction is done at the same temperature
PCl₅ (g) ⇋ PCl₃ (g) + Cl₂ (g) PCl₅ (g) decomposes into PCl₃ (g) and Cl₂ (g) according to the equation above. A pure sample of PCl₅ (g) is placed in a rigid, evacuated 1.00 L container. The initial pressure of the PCl₅ (g) is 1.00 atm. The temperature is held constant until the PCl₅ (g) reaches equilibrium with its decomposition products. The figures below show the initial and equilibrium conditions of the system: Figure 1 - initial - PCl₅ Ptotal= 1.00 atm Figure 2 - equilibrium - PCl₅, PCl₃, Cl₂ Ptotal= 1.40 atm As the reaction progresses toward equilibrium, the rate of the forward reaction...
decreases to become a constant nonzero rate at equilibrium
Ag₂CO₃ (s) ⇋ 2Ag+ (aq) + CO₃²⁻ (aq) The chemical equation above represents the equilibrium that exists in a saturated solution of Ag₂CO₃. If S represents the molar solubility of Ag₂CO₃, which of the following mathematical expressions shows how to calculate S based on Ksp?
s = cubic root (Ksp/4)
H₂ gas and N₂ gas were placed in a rigid vessel and allowed to reach equilibrium in the presence of a catalyst according to the following reaction: 3H₂ (g) + N₂ (g) ⇋ 2NH₃ (g) ▵H° = -92 kJ/molrxn The diagram below shows how the concentrations of H₂, N₂, and NH₃ in this system changed over time. *Even out and have a slope of zero from t1 onward to t2* Which of the following was true for the system between time t1 and time t2?
the rates of the forward and reverse reactions were equal
FeF₂ (s) ⇋ Fe²⁺ (aq) + 2 F- (aq) | K₁ = 2 x 10⁻⁶ F⁻ (aq) + H⁺ (aq) ⇋ HF (aq) | K₂ = 1 x 10³ FeF₂ (s) + 2H⁺ (aq) ⇋ Fe²⁺ (aq) + 2HF (aq) | K₃ = ? On the basis of the information above, the dissolution of FeF₂ (s) in acidic solution is
thermodynamically favorable because K₃>1
Equimolar samples CH₃OH (l) and C₂H₅OH (l) are placed in separate, previously evacuated, rigid 2.0 L vessels. Each vessel is attached to a pressure gauge, and the temperatures are kept at 300 K. In both vessels, liquid is observed to remain present at the bottom of the container at all times. The change in pressure inside the vessel containing CH₃OH (l) is shown below. *Pressure levels out at 0.196 atm and slope is zero* The value of Kₚ for the evaporation of CH₃OH (l) at 300 K is closest to...
0.2
How many moles of NaF must be dissolved in 1.00 liter of a saturated solution of PbF₂ at 25 ̊C to reduce the [Pb2+] to 1 x 10⁻⁶ molar? (Ksp PbF₂ at 25 ̊C = 4.0 x 10⁻⁸)
0.20 mole
CaF₂ (s) ⇋ Ca²⁺ (aq) + 2F- (aq) | Ksp = 1.5 x 10⁻¹¹ The concentration of F- (aq) in drinking water that is considered to be ideal for promoting dental health is 4.0 x 10⁻⁵ M. Based on the information above, the maximum concentration of Ca²⁺ (aq) that can be present in drinking water without lowering the concentration of F- (aq) below the ideal level is closest to...
0.0094 M
COCl₂ (g) ⇋ CO (g) + Cl₂ (g) COCl₂ (g) decomposes according to the equation above. When pure COCl₂ (g) is injected into a rigid, previously evacuated flask at 690 K, the pressure in the flask is initially 1.0 atm. After the reaction reaches equilibrium at 690 K, the total pressure in the flask is 1.2 atm. What is the value of Kₚ for the reaction at 690 K?
0.050
CaF₂ (s) ⇋ Ca²⁺ (aq) + 2F- (aq) △H > 0 Dissolution of the slightly soluble salt CaF₂ is shown by the equation above. Which of the following changes will decrease [Ca2+] in a saturated solution of CaF₂ , and why? (Assume that after each change some CaF₂ (s) remains in contact with the solution.)
Adding NaF(s), because the reaction will proceed toward reactants
N₂ (g) + 3H₂ (g) ⇋ 2NH₃ (g) | △H<0 NH₃ (g) was synthesized at 200°C in the presence of a powdered Os(s) catalyst, leading to the equilibrium system represented above. Which of the following changes would result in more NH₃ (g) in the mixture after equilibrium is reestablished?
Adding some N₂ (g)
Ag + (aq) + NH₃ (aq) ⇋ Ag(NH₃)+ (aq) | Keq₁ = 2.1 x 10³ Ag(NH₃)+ (aq) + NH₃ (aq) ⇋ Ag(NH₃)₂+ (aq) | Keq₂ = 8.2 x 10³ Equal volumes of 0.1 M AgNO₃ (aq) and 2.0 M NH₃ (aq) are mixed and the reactions represented above occur. Which Ag species will have the highest concentration in the equilibrium system shown below, and why? Ag + (aq) + 2NH₃ (aq) ⇋ Ag(NH₃)₂+ (aq) | Keq₃ = ?
Ag(NH₃)₂+ (aq), because Keq₃= 1.7 x 10⁷
As solution pH increases, Ag+ concentration decreases A student investigates the effects of pH on the solubility of AgOH (s), which dissolves in water according to the equation AgOH (s) ⇋ Ag+ (aq) + OH- (aq). The value for Ksp for AgOH is 2.0 x 10 ⁸ at 298 K. The student places the same mass of Ag(OH) into 50.00 mL of different solutions with specific pH values and measures the concentration of Ag+ ions in each solution after equilibrium is reached. Based on the data in the table, what can be concluded about the solubility of AgOH?
AgOH is less soluble at higher because higher concentrations of OH- (aq) shift the solubility equilibrium toward solid AgOH.
A sample of N₂O₄ (g) is placed in an evacuated container at 373 K and allowed to undergo the reversible reaction: N₂O₄ (g) ⇋ 2NO₂ (g). The concentration of each species is measured over time, and the data are used to make the graph shown above. Which of the following identifies when equilibrium is first reached and provides a correct explanation? *Slope of N₂O₄ and NO₂ evens out and becomes zero after 60 seconds*
At 60 seconds, because [NO₂] and [N₂O₄] remains constant, indicating that the forward and reverse reaction rates are equal.