AP Chemistry Possible Questions Bank
2HI(g)⇄H2(g)+I2(g) Kp=PH2PI2P2HI=0.0016 The decomposition of HI(g) at 298K 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 3.7torr. 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? A PI2≈14 torr, because it is directly proportional to the square of the initial pressure of HI. B PI2≈0.073 torr, because it is inversely proportional to the square of the initial pressure of HI. C PI2≈7.4 torr, because it is directly proportional to the initial pressure of HI. D PI2≈1.9 torr, because it is inversely proportional to the initial pressure of HI.
C. PI2≈7.4 torr, because it is directly proportional to the initial pressure of HI.
Reaction 1: NO3(g)+NO2(g)⇄N2O5(g) K=2.6×10−11 In the atmosphere, small water droplets are suspended in the air, forming an aerosol. N2O5(g) can form HNO3(aq) under these conditions, as shown in reaction 2, represented below. Reaction 2:N2O5(g)+H2O(l)→2HNO3(aq) Which of the following predicts the effect that the formation of HNO3(aq) will have on the equilibrium shown in reaction 1, and why? A The equilibrium of reaction 1 will shift toward the formation of more product, because N2O5(g) is removed when it reacts to form HNO3(aq). B The equilibrium of reaction 1 will shift toward the formation of more product, because H2O(l) acts as a catalyst for reaction 1. C The equilibrium of reaction 1 will shift toward the formation of more reactants, because the product N2O5(g) is removed when it reacts to form HNO3(aq). D The equilibrium of reaction 1 is not affected, because neither H2O(l) nor HNO3(aq) are gases.
A The equilibrium of reaction 1 will shift toward the formation of more product, because N2O5(g) is removed when it reacts to form HNO3(aq).
Reaction 1: NO3(g)+NO2(g)⇄N2O5(g) K=2.6×10−11 In the atmosphere, small water droplets are suspended in the air, forming an aerosol. N2O5(g) can form HNO3(aq) under these conditions, as shown in reaction 2, represented below. Reaction 2:N2O5(g)+H2O(l)→2HNO3(aq) Which of the following predicts the effect that the formation of HNO3(aq) will have on the equilibrium shown in reaction 1, and why?
A The equilibrium of reaction 1 will shift toward the formation of more product, because N2O5(g)N2O5(g) is removed when it reacts to form HNO3(aq)HNO3(aq).
A saturated aqueous solution of CdF2 is prepared. The equilibrium in the solution is represented above. In the solution, [Cd2+]eq=0.0585M and [F−]eq=0.117M. Some 0.90MNaF 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? CdF2(s)⇄Cd2+(aq)+2F−(aq)
A The molar solubility of CdF2CdF2 in pure water is 0.0585M0.0585M, and adding NaFNaF decreases this solubility because the equilibrium shifts to favor the precipitation of some CdF2CdF2.
A chemist carried out the reaction at 573K, starting with 0.100mol of each reactant in a 1.00L container with variable volume. The reaction mixture quickly reached equilibrium, as indicated in the graph above. The chemist reduces the volume of the equilibrium system by half while keeping the temperature constant. Which of the following predictions about the yield of the reaction is best, and why?
A. By halving the volume, the pressure doubles. The system will respond to the increase in pressure by decreasing the total number of moles of gas in the system. Thus, the yield will increase because the reaction will shift toward more product.
The table above provides the Keq values for two reactions. Which of the following is the correct mathematical expression needed to determine the equilibrium constant of the reaction shown below?
A. K3=K1×1/K2
At a given temperature, the system represented by the chemical equation above is at equilibrium inside a rigid container. Which of the following explains how the system will restore equilibrium, based on the correct relationship between Q and K, after a certain amount of Cl2(g) is added?
A. Since Q=[Cl2][CO]/[COCl2], when Cl2(g) is added to the system Q>KQ>K and the system will restore equilibrium by producing more COCl2(g)
The particle diagram above shows the system represented by the equation 2X(g)+Y2(g)⇄2XY(g) . Which of the following explains whether the particle diagram indicates that the system is at equilibrium?
A. The particle diagram does not indicate that the system is at equilibrium because it shows the system only at one point in time.
Which of the following best explains what the particle diagram is able to show about the entropy change for the dissolution of CuCl(s) in pure water?
A. The particle diagram shows that the dissociation of CuCl(s) into ions contributes to an increase in the entropy for the dissolution.
Which of the following best explains whether or not the particle diagram can predict the relative value of the enthalpy change for the dissolution of CuCl(s) ?
A. The value of the enthalpy change for the dissolution of CuCl(s) cannot be predicted from the particle diagram because it fails to illustrate the amount of energy required to overcome the forces between solute particles and between solvent particles.
Cu2+(aq) absorbs a certain frequency of visible light. Absorbance was measured for three saturated solutions of Cu(OH)2, each at a different pH at 298K. Based on the data recorded in the table above, which of the following conclusions about the effect of pH on the solubility of Cu(OH)2 can be made?
A. When the concentration of H+ ions is increased, the solubility of Cu(OH)2 increases.
Reaction 1: HOCl(aq)+H2O(l)⇄H3O+(aq)+OCl−(aq)K1=[H3O+][OCl−][HOCl]Reaction 2: 2H2O(l)⇄H3O+(aq)+OH−(aq)K2=[H3O+][OH−]Reaction 3: OCl−(aq)+H2O(l)⇄HOCl(aq)+OH−(aq)K3=? Based on the equilibrium constants given above, which of the following gives the correct expression for the equilibrium constant for reaction 3? A K3=K2K1 B K3=K1K2 C K3=K1K2 D K3=1K1K2
A. K3= k2/k1
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=0.0585M and [F−]eq=0.117M. Some 0.90MNaF 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? A The molar solubility of CdF2 in pure water is 0.0585M, and adding NaF decreases this solubility because the equilibrium shifts to favor the precipitation of some CdF2. B The molar solubility of CdF2 in pure water is 0.0585M, and adding NaF has no effect on the solubility because only changes in temperature can increase or decrease the molar solubility of an ionic solid. C The molar solubility of CdF2 in pure water is 0.117M, and adding NaF decreases this solubility because the equilibrium shifts to favor the precipitation of some CdF2
A. The molar solubility of CdF2 in pure water is 0.0585M, and adding NaF decreases this solubility because the equilibrium shifts to favor the precipitation of some CdF2.
COCl2 decomposes according to the equation above. When pure COCl2 is injected into a rigid, previously evacuated flask at 690 K, the pressure in the flask is initially 1.0 atm. After the reaction reached 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?
B
The synthesis of NH3 is represented by the equation above. Based on the equilibrium constant K, and ΔH rxn given above, which of the following can best be used to justify that the reaction is thermodynamically favorable at 298 K and constant pressure?
B
An equimolar mixture of X(g) and Y(g) is placed inside a rigid container at constant temperature. The particle diagram above represents the changes that occur over time. Based on the particle diagram, which of the following best predicts whether or not the system has reached equilibrium by 300s?
B It is not possible to determine that the system has reached equilibrium by 300s300s because the amounts of XX, YY, and XYXY have continued to change
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) A Region A, because the initial pressure inside the cylinder is equal to the pressure outside the cylinder, so there is no net force on the piston. B Region B, because the pressure inside the cylinder is equal to the vapor pressure of water at 80∘C when both liquid and gas phases are present. C R
B Region B, because the pressure inside the cylinder is equal to the vapor pressure of water at 80∘C when both liquid and gas phases are present.
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 of KSCN(s) results in the red color of the solution becoming deeper? Fe3+(aq)Colorless+ SCN−(aq)Colorless⇄ FeSCN2+(aq)Red
C The added KSCN(s)KSCN(s) dissolves, causing the reaction system to respond by producing more product to partially consume SCN−(aq)SCN−(aq) and reduce its concentration.
HCl(aq)+H2O(l)⇄H3O+(aq)+Cl−(aq) In 1.0MHCl(aq), HCl is nearly 100 percent dissociated, as represented by the equation above. Which of the following best helps to explain why, in 0.01MHCN(aq), less than 1 percent of HCNis dissociated? A The CN− ion is not very soluble in water, and a solid precipitate would form if more of the HCN dissociated. B Compared to the HCl(aq) solution, the concentration of the HCN(aq) solution is much too dilute to achieve 100 percent dissociation. C The equilibrium constant for the dissociation of HCN(aq) is much smaller than that for the dissociation of HCl(aq). D HCN(aq) reacts with water to form a basic solution, and the high concentration of OH−(aq) interferes with the dissociation process.
C The equilibrium constant for the dissociation of HCN(aq) is much smaller than that for the dissociation of HCl(aq).
In 1.0MHCl(aq), HCl is nearly 100 percent dissociated, as represented by the equation above. Which of the following best helps to explain why, in 0.01MHCN(aq), less than 1 percent of HCN is dissociated? HCl(aq)+H2O(l)⇄H3O+(aq)+Cl−(aq)
C The equilibrium constant for the dissociation of HCN(aq)HCN(aq) is much smaller than that for the dissociation of HCl(aq)HCl(aq).
The particle diagram above illustrates the changes that take place when X(g) and Y(g) are placed inside a rigid container at constant temperature. Which of the following is a characteristic of a system at equilibrium that is best represented by the particle diagram? X(g)+Y(g)⇄XY(g)
C The particle diagram shows that after 200s200s there are no observable changes in the amounts of reactants and products, which is a characteristic of a system at equilibrium.
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 0.0100M. The following table shows the concentrations of the gases at equilibrium at a particular temperature. [A]eq[B]eq[C]eq0.01800.01400.0020 If the experiment is repeated at a higher temperature at which Kc is larger, which of the following best describes the effect of the temperature change on the concentrations of the gases at equilibrium? A [A]eq, [B]eq, and [C]eq will all increase because Kc increased. B [A]eq and [B]eq will remain constant, but [C]eq will increase because Kcincreased. C There will be a decrease in [A]eq that will be two times the decrease in [B]eqbecause A and B react in a 2-to-1 ratio. D There will be an increase in [A]eq that will be two times the increase in [B]eqbecause A and
C There will be a decrease in [A]eq that will be two times the decrease in [B]eqbecause A and B react in a 2-to-1 ratio.
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)
B Region B, because the pressure inside the cylinder is equal to the vapor pressure of water at 80∘C80∘C when both liquid and gas phases are present.
The equilibrium constants for the dissolution (Ksp) 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 (S) of some of these substances based on their Ksp ?
B The molar solubilities for CuCNCuCN and NiCO3NiCO3 are calculated using S=Ksp−−−√S=Ksp and CuCNCuCN has a lower molar solubility than NiCO3NiCO3.
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? A The molar solubility of MgCO3 decreases with increasing acidity (lower pH). B The molar solubility of MgCO3 increases with increasing acidity (lower pH). C The pH or acidity of the solution has a negligible effect on the molar solubility of MgCO3. D From the data it is not possible to determine the effect of changes in acidity on the molar solubility of MgCO3.
B The molar solubility of MgCO3 increases with increasing acidity (lower pH).
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? MgCO3(s)⇄Mg2+(aq)+CO32−(aq)
B The molar solubility of MgCO3MgCO3 increases with increasing acidity (lower pHpH).
AgCl(s) ⇄ Ag+(aq)+Cl−(aq)Ksp=1.8×10−10 Shown above is information about the dissolution of AgCl(s) in water at 298K. 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−]=0.010M) instead of distilled water and the student did not account for the Cl− in the tap water? A The value obtained for Ksp would be too small because Cl−(aq) ions would be attracted to the Ag+ ions in the AgCl crystals, thus preventing water molecules from reaching the crystals. B 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. C The value obtained for Ksp would be too large becau
B 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.
SubstanceYZInitial concentration (M)2.00.0Equilibrium concentration (M)1.20.80 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, Kc, at 490K. 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?
B [Y]eq≈1.5 M[Y]eq≈1.5 M because the ratio [Z]eq[Y]eq[Z]eq[Y]eq should remain constant when the reaction is done at the same temperature.
At a certain temperature, SO2(g) and O2(g) react to produce SO3(g) according to the chemical equation shown above. An evacuated rigid vessel is originally filled with SO2(g) and O2(g), each with a partial pressure of 1atm. Which of the following is closest to the partial pressure of O2(g) after the system has reached equilibrium, and why?
B. 0.5atm; because Kp is very large, nearly all the SO2(g) is consumed before the system reaches equilibrium, but an excess amount of O2(g) remains at equilibrium.
The equilibrium in a saturated solution of Ca(OH)2 is represented above. In an experiment, a student places 5.0g of Ca(OH)2(s) into 100.0mL of distilled water and stirs the mixture. How would the results be affected if the student repeats the experiment but this time places 5.0g of Ca(OH)2(s) into 100.0mL of 0.0010MNaOH(aq) instead of distilled water?
B. Less solid will dissolve, because the larger value of [OH−] will cause the equilibrium position to lie farther to the left.
Which of the following changes to the particle diagram will best represent the effect of adding 1.0mL of 4MNaCl to the solution?
B. Some of the Cu+ and Cl− ions combine to form CuCl(s) because the molar solubility will be lower than 4×10−4M
A student poured 10mL of CoCl2(aq) into a test tube and added a few drops of concentrated HCl, which resulted in a deep-blue solution. The reaction that occurred is represented by the chemical equation shown above. Then, the student placed the test tube inside a beaker that contained ice and water for about five minutes. Which of the following describes what the student most likely observed next, and why?
B. The color of the solution changed from blue to pink, because cooling caused the equilibrium to shift to form the pink-colored Co(H2O)62+.
The equilibrium reaction in 0.100M HBrO(aq) at equilibrium is represented by the equation above. Based on the magnitude of the equilibrium constant, which of the following correctly compares the equilibrium concentrations of substances involved in the reaction, and why?
B. The equilibrium concentration of BrO− will be much smaller than the equilibrium concentration of HBrO, because Keq<<1
An equimolar mixture of X(g) and Y(g) is placed inside a rigid container at constant temperature. The particle diagram above represents the changes that occur over time. Based on the particle diagram, which of the following best predicts whether or not the system has reached equilibrium by 300s? A It is not possible to determine that the system has reached equilibrium by 300s because the stoichiometry of the reaction is not known. B It is not possible to determine that the system has reached equilibrium by 300s because the amounts of X, Y, and XY have continued to change. C The system has reached equilibrium by 300s because the rate of formation of XY is constant. D The system has reached equilibrium by 300s because the rates of consumption of X and Y are equal.
B. It is not possible to determine that the system has reached equilibrium by 300s because the amounts of X, Y, and XY have continued to change.
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 0.0100M. The following table shows the concentrations of the gases at equilibrium at a particular temperature. [A]eq[B]eq[C]eq0.01800.01400.0020 If the experiment is repeated at a higher temperature at which Kc is larger, which of the following best describes the effect of the temperature change on the concentrations of the gases at equilibrium?
C There will be a decrease in [A]eq[A]eq that will be two times the decrease in [B]eq[B]eq because AA and BB react in a 2-to-1 ratio
The table above shows data for two reactions carried out in two separate evacuated 1.0-liter rigid containers at constant temperature of 298K. To each container 0.50mol 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 containers at equilibrium? ReactionEquilibrium Reactions at 298KKeq1Br2(g)+Cl2(g)⇄2BrCl(g)10.2N2(g)+O2(g)⇄2NO(g)4.2×10−31
C [BrCl]eq>[NO]eq[BrCl]eq>[NO]eq because the much larger KeqKeq for reaction 1 means that a much higher concentration of products will be present at equilibrium for reaction 1 compared with reaction 2.
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. Based on the data, which of the following claims is most likely correct? A The reaction was about to reach equilibrium 15 minutes after the reactants were combined because the concentrations of X and XY were almost the same. B The reaction reached equilibrium between 75 minutes and 155 minutes after the reactants were combined because the concentrations of X and XYremained constant. C The reaction did not reach equilibrium because only 86% of the initial concentration of X was consumed. D The reaction did not reach equilibrium because initially there was no XYinside the container.
B. The reaction reached equilibrium between 75 minutes and 155 minutes after the reactants were combined because the concentrations of X and XYremained constant.
The decomposition of HI(g) at 298K 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 3.7torr. 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? 2HI(g)⇄H2(g)+I2(g) Kp=PH2PI2P2HI=0.0016
C PI2≈7.4 torrPI2≈7.4 torr, because it is directly proportional to the initial pressure of HIHI.
Fe3+(aq)Colorless+ SCN−(aq)Colorless⇄ FeSCN2+(aq)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 of KSCN(s) results in the red color of the solution becoming deeper? A The added KSCN(s) dissolves, disturbing the charge balance in the solution, causing Fe(SCN)3 to precipitate as a red solid. B The added KSCN(s) dissolves, causing the solution to become saturated in SCN− ions, which appear red at high concentrations. C The added KSCN(s) dissolves, causing the reaction system to respond by producing more product to partially consume SCN−(aq) and reduce its concentration. D The added KSCN(s) dissolves, causing the reaction system to respond by forming more Fe3+ ions, which have a deep orange color
C The added KSCN(s) dissolves, causing the reaction system to respond by producing more product to partially consume SCN−(aq) and reduce its concentration.
Reaction 1: NO3(g)+NO2(g)⇄N2O5(g) K=2.6×10−11 During the day, solar radiation is absorbed by NO3(g), resulting in its decomposition. Which of the following best explains whether the equilibrium concentration of N2O5(g) in the atmosphere in the daytime is different from that in the nighttime, and why? A [N2O5] will be higher during the day, because the decomposition of NO3(g)results in an increase in the rate of production of N2O5(g). B [N2O5] will be higher during the day, because NO2(g) will be in excess, leading to an increase in the rate of production of N2O5(g). C [N2O5] will be higher at night, because the decomposition of NO3(g) in the daytime will result in an increase in the rate of consumption of N2O5(g) to reform NO3(g). D [N2O5] will be about the same at nighttime and daytime, because the amount of NO2(g) will not be changed and the equilibrium will not be affected.
C [N2O5] will be higher at night, because the decomposition of NO3(g) in the daytime will result in an increase in the rate of consumption of N2O5(g) to reform NO3(g).
During the day, solar radiation is absorbed by NO3(g), resulting in its decomposition. Which of the following best explains whether the equilibrium concentration of N2O5(g) in the atmosphere in the daytime is different from that in the nighttime, and why? Reaction 1: NO3(g)+NO2(g)⇄N2O5(g) K=2.6×10−11
C [N2O5][N2O5] will be higher at night, because the decomposition of NO3(g)NO3(g) in the daytime will result in an increase in the rate of consumption of N2O5(g)N2O5(g) to reform NO3(g)NO3(g).
For which of the following salts would the relationship between molar solubility, s, in mol/L, and the value of Ksp be represented by the equation Ksp=4s3
C. Ag2SO4
CaF2(s) dissolves in water according to the equation CaF2(s)⇄Ca2+(aq)+2 F−(aq). The value of Ksp for the dissolution is 3.5×10−11. A student measures the concentration of Ca2+ ions in a saturated solution of CaF2 at various pH values and uses those values to generate the graph above. Based on the data, which of the following observations about the solubility of CaF2 is most valid?
C. It is higher at a lower pH; there are more H+ ions in solution at low pH, so HF forms and shifts the equilibrium reaction above to the right.
In an experiment involving the reaction shown above, a sample of pure HI was placed inside a rigid container at a certain temperature. The table above provides the initial and equilibrium concentrations for some of the substances in the reaction. Based on the data, which of the following is the value of the equilibrium constant (Keq) for the reaction, and why?
C. Keq=1.6×10−2, because [I2]eq=[H2]eq
Which of the following indicates the equilibrium value of PCl2 and the approximate value of the equilibrium constant Kp ?
C. PCl2=0.20atm and Kp=20.
A saturated solution of Hg2I2 is at equilibrium at 25°C as represented by the equation above. If [I−]=4.6×10−10 M at equilibrium, which of the following gives the correct molar solubility, S, and Ksp for Hg2I2 ?
C. S=2.3×10−10 M; Ksp=(2.3×10−10)(4.6×10−10)2
The dissolution of AgI is represented above. Which of the following shows the mathematical relationship between the molar solubility, S, of AgI and the Ksp at 298K?
C. S=√8.3×10−17 mol/L
The formation of FeSCN2+ in an aqueous solution is represented by the chemical equilibrium shown above. A light red-brown solution is prepared combining 12.50mL of 0.5MFe(NO3)3 , 0.5mL of 0.002MKSCN, and 37.0mL of water that had been slightly acidified. If an additional 1.0mL of 0.5MFe(NO3)3 is added, which of the following predicts and explains correctly whether the darkness of the color of the solution will change?
C. The color of the solution will darken because the equilibrium will favor the formation of more FeSCN2+
The particle diagrams above show the changes that occurred after an equimolecular mixture of X(g) and Y(g) was placed inside a rigid container at constant temperature. Which of the following statements is be best supported by the particle diagrams?
C. The forward reaction has a faster rate than the reverse reaction between 0s and 300s because more products were being formed.
The dissolution of solid AgCN is represented by the chemical equation above. In pure water, the equilibrium concentration of Ag+ ions in a saturated solution is 7.7×10−9M. If a small amount of solid NaCN is added to the saturated AgCN solution, which of the following would be observed?
C. The molar solubility of AgCN becomes smaller than 7.7×10−9M and some AgCN precipitates.
The chemical reaction shown above took place inside a rigid container at constant temperature. The table provides the concentrations of reactants and products at some point during the reaction. Based on this information, which of the following explains whether or not the reaction has reached equilibrium, and why?
C. The reaction is not at equilibrium because Qc<Kc; the forward reaction is favored in order to form more XY.
A sample of pure NO2(g) in a sealed tube at 20°C is placed in a temperature bath at 30°C. Observations of changes in the color, pressure, and mass of the mixture are recorded as a function of time. Which of the following is an observation that would best support the claim that the reaction represented above has reached equilibrium at 30°C?
C. The total pressure of the system decreases then reaches a constant value because at equilibrium the amounts of reactant and product no longer change.
Shown above are a chemical equation that represents the dissolution of PbBr2 in pure water, a table of the changes in some thermodynamic properties for the process, and a particle diagram. Which of the following explains which relative change in a thermodynamic property is best illustrated by the particle diagram?
C. The very small amount of Pb2+ and Br− ions illustrates that ΔG°>0 because the dissolution of PbBr2 is not a favorable process.
The diagram above represents the equilibrium between two isomers of 2-butene. The equilibrium constant, Kc, is 1.2 at a certain temperature. Two identical vessels each contain an equilibrium mixture of the two gases at that temperature. The concentration of cis‑2‑butene in the second vessel is twice the concentration in the first vessel. What is the concentration of trans‑2‑butene in the second vessel compared to that in the first vessel?
C. Twice the concentration of that in the first vessel
A sample of acetone is placed into a container. The container is sealed and attached to a pressure sensor, as shown in the diagram above. The container is allowed to sit on the lab table for a few minutes as the pressure in the container is monitored at regular intervals. At the end of 2.00 minutes, some acetone liquid remains in the container. Which of the following best explains the pressure data presented in the table above?
C. The acetone vaporizes from the liquid at a constant rate and the rate of condensation increases until it becomes equal to the rate of evaporation and the pressure stays constant.
X2(g)+Y2(g)⇄2XY(g)Kc=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 product as the system moves toward equilibrium?
0.30, M 0.30 M, 0.90 M
N2(g)+3H2(g)⇄2NH3(g) A 2.0L reaction vessel contains an equilibrium mixture of the system represented above. The partial pressures of the components of the mixture at equilibrium are listed in the table below.
1.00 atm < P total < 2.00 atm
N2O5(g) ⇄ 2 NO2(g) + ½ O2(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) + 4 NO2(g) ⇄ 2 N2O5(g)
1/(95)^2
ICl(g)⇄12I2(g)+12Cl2(g)Keq=0.1 Based on the information above, what is the value of Keq for the reaction represented below? I2(g)+Cl2(g)⇄2ICl(g)
100
2 NO2(g) ⇄ N2O4(g) dark brown colorless The dimerization of NO2(g) , an exothermic process, is represented by the equation above. 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 Kc at this temperature if 0.00500 mol of N2O4(g) is present at equilibrium?
12.5
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 PN204 is 1.33 atm when the system is at equilibrium at 70°C, what is PNO2
2.0 atm
According to the information about the dissolution of Ba(IO3)2 shown above, the correct value of S, the molar solubility of Ba(IO3)2, can be calculated using with of the following mathematical relationships?
4S^3 = 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
Reaction 1:HOCl(aq)+H2O(l)⇄H3O+(aq)+OCl−(aq)K1=[H3O+][OCl−][HOCl]Reaction 2:2H2O(l)⇄H3O+(aq)+OH−(aq)K2=[H3O+][OH−]Reaction 3:OCl−(aq)+H2O(l)⇄HOCl(aq)+OH−(aq)K3=? Based on the equilibrium constants given above, which of the following gives the correct expression for the equilibrium constant for reaction 3?
A K3=K2K1
X(g)+Y(g)⇄XY(g) The particle diagram above illustrates the changes that take place when X(g) and Y(g) are placed inside a rigid container at constant temperature. Which of the following is a characteristic of a system at equilibrium that is best represented by the particle diagram? A The particle diagram shows that initially the reaction proceeds to the right to form products, which is a characteristic of a system at equilibrium. B The particle diagram shows that after 200s the rate of the reverse reaction is slower than the rate of the forward reaction, which is a characteristic of a system at equilibrium. C The particle diagram shows that after 200s there are no observable changes in the amounts of reactants and products, which is a characteristic of a system at equilibrium. D The particle diagram shows that between 0s and 200s the rates of the forward and reverse reactions are the same, which is a characteristic
C. The particle diagram shows that after 200s there are no observable changes in the amounts of reactants and products, which is a characteristic of a system at equilibrium.
The table above shows data for two reactions carried out in two separate evacuated 1.0-liter rigid containers at constant temperature of 298K. To each container 0.50mol 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 containers at equilibrium? A [BrCl]eq=[NO]eq because equimolecular mixtures of the reactants were allowed to reach equilibrium at the same constant temperature. B [BrCl]eq>[NO]eq because Br2 and Cl2 are larger molecules that can collide more frequently to form products. C [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 with reaction 2. D [BrCl]eq<[NO]eq because the much larger Keq for reaction 1 means tha
C. [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 with reaction 2.
Ca(OH)2 precipitates when a 1.0 g sample of CaC2 is added to 1.0 L of distilled water at room temperature. If a 0.064 g sample of CaC2 (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
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 with of the following mathematical relationships? Ba(IO3)2(s) ⇄ Ba2+(aq) + 2 IO3−(aq) Ksp=4×10−9
D 4S3=4×10−9 M4S3=4×10−9 M
A sample of N2O4(g) is placed into an evacuated container at 373K 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? A At 14 seconds, because [N2O4] is twice [NO2], which implies that the forward and reverse reaction rates are equal. B At 23 seconds, because [NO2] equals [N2O4], which shows that equal concentrations are present at equilibrium. C At 40 seconds, because [NO2] is twice [N2O4], which matches the stoichiometry of the balanced chemical equation. D At 60 seconds, because [NO2] and [N2O4] remain constant, indicating that the forward and reverse reaction rates are equal.
D. At 60 seconds, because [NO2] and [N2O4] remain constant, indicating that the forward and reverse reaction rates are equal.
The exothermic dissolution of Mg(OH)2 in water is represented by the equation above. The Ksp of Mg()H)2 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
CO(g) + 2 H2(g) ⇄ CH3OH(g) ΔH < 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 mixture of CO(g) and H2(g) is pumped into a previously evacuated 2.0 L reaction vessel. The total pressure of the reaction system is 1.2 atm at equilibrium. What will be the total equilibrium pressure of the system if the volume of the reaction vessel is reduced to 1.0 L at constant temperature?
Greater than 1.2 atm but less than 2.4 atm
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)
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 2.0×10−8 at 298K. The student places the same mass of AgOH(s) into 50.0mL 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? A The solubility of AgOH is unaffected by pH because Ksp is a constant value at 298K. B The solubility of AgOH is unaffected by pH because it is the same value for pH 7.00 and pH 8.00. C AgOH is more soluble at higher pH because lower concentrations of OH−(aq) shift the solubility equilibrium toward Ag+(aq) and OH−(aq). D AgOH is less soluble at higher pH because higher concentrations of OH−(aq) shift the solubility equilibrium toward solid
D AgOH is less soluble at higher pH because higher concentrations of OH−(aq) shift the solubility equilibrium toward solid AgOH.
The decomposition of HI at 298 K is represented by the equilibrium equation above. When 100. torr of HI is added to a previously evacuated, rigid container and allowed to reach equilibrium, the partial pressure of I2 repeated at the same temperature, which of the following correctly predicts the equilibrium partial pressure I2 and why?
I2 = 7.4 torr, because it is directly proportional to the initial pressure of HI.
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. Based on the data, which of the following claims is most likely correct? 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. Based on the data, which of the following claims is most likely correct?
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)CO(g)+3H2(g)⇄CH4(g)+H2O(g)K1=[CH4][H2O][CO][H2]3K1=[CH4][H2O][CO][H2]3 Reaction 2:CO2(g)+H2(g)⇄CO(g)+H2O(g)CO2(g)+H2(g)⇄CO(g)+H2O(g)K2=[CO][H2O][CO2][H2]K2=[CO][H2O][CO2][H2] Reaction 3:CH4(g)+2H2O(g)⇄CO2(g)+4H2(g)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
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
Based on the equilibrium constants given above, which of the following gives the correct expression for the equilibrium constant for reaction 3?
K3 = K2/K1
The table above lists some equilibrium systems and their equilibrium constants. Which of the following identifies the correct mathematical relationship that uses the information to calculate K5?
K5 = K1 x K3 / K4
A sample of POCl3 is placed in a closed, rigid container at 298 K and allowed to reach equilibrium according to the equation above. Based on the value for ΔG rxn = +490 kJ/mol, which of the following is true?
K=e^-490,000/8.314 x 298 << 1 and at equilibrium POCl3 >> PCl3
CO(g) + 2 H2(g) ⇄ CH3OH(g) Δ 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.
2 BaO2(s) ⇄ 2 BaO(s) + O2(g) ΔH°= 162 kJ/molrxn A sealed rigid vessel contains BaO2(s) in equilibrium with BaO(s) and O2(g) as represented by the equation above. Which of the following changes will increase the amount of BaO2(s) in the vessel?
Lowering the temperature
CaCO3(s) ⇄ CaO(s) + CO2(g) ΔH° = 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. 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) ⇌ 2 HI(g) Kc = 50. at 600°C Equimolar samples of each of three gases, H2(g), I2(g), and HI(g) , are introduced into a 3.0 L container that is heated to 600°C. According to the information above, which of the following will occur as the system approaches equilibrium?
More HI(g) will be produced because Q < Kc .
H2(g) + I2(g) ⇄ 2 HI(g) At 450oC, 2.0 moles each of H2(g), I2(g), and HI(g) are combined in a 1.0 L rigid container. The value of Kc at 450oC is 50. Which of the following will occur as the system moves toward equilibrium?
More HI(g) will form.
For which of the equilibrium systems represented below will the amount of product(s) at equilibrium increase if the volume of the reaction vessel is increased at a constant temperature?
PCl5(g) ⇄ PCl3(g) + Cl2(g)
2HI(g)⇄H2(g)+I2(g) Kp=PH2PI2P2HI=0.00162 The decomposition of HI(g) at 298K 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 3.7torr. 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.
based on the Ksp values in the table above, a saturated solution of which of the following compounds has the highest [Cl]?
PbCl2
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 NOBr because the reverse reaction is faster than the forward reaction.
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
2NO(g)+Br2(g)⇄2NOBr(g) Kp=(PNOBr)2(PNO)2(PBr2)=28 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/(10.0)^2(2.0) > Kp and equilibrium will be approached by consuming NOBr because the reverse reaction is faster than the forward reaction.
2NO(g)+Cl2(g)⇄2NOCl(g) Kc=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. 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.
The equilibrium reaction between Cl2 and H2O 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 Qc and predicts the response by the system immediately after dilution?
Qc = Ke/4, and the rate of the forward reaction will be greater that the rate of the reverse reaction
Cl2(aq)+2H2O(l)⇄H3O+(aq)+Cl−(aq)+HOCl(aq) Kc=[H3O+][Cl−][HOCl][Cl2]=4.8×10−4 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 Qc and predicts the response by the system immediately after dilution?
Qc= Kc/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∘C80∘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?
Region B, because the pressure inside the cylinder is equal to the vapor pressure of water at 80∘C when both liquid and gas phases are present.
A sealed rigid vessel contains BaO2 in equilbrium with BaO and O2 as requested by the equation above. Which of the following changes will increase the amount of BaO2 in the vessel?
Removing a small amount of BaO
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 2.0×10−8 at 298K. The student places the same mass of AgOH(s) into 50.0mL 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?
D AgOHAgOH is less soluble at higher pHpH because higher concentrations of OH−(aq)OH−(aq) shift the solubility equilibrium toward solid AgOHAgOH.
A sample of N2O4(g) is placed into an evacuated container at 373K 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?
D At 60 seconds, because [NO2][NO2] and [N2O4][N2O4] remain constant, indicating that the forward and reverse reaction rates are equal.
Reaction 1: CO(g)+3H2(g)⇄CH4(g)+H2O(g)K1=[CH4][H2O][CO][H2]3Reaction 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? A K3=(−K1)+(−K2) B K3=(−K1)−(−K2) C K3=K1×K2 D K3=1K1×1K2
D K3=1/K1×1/K2
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? Reaction 1:CO(g)+3H2(g)⇄CH4(g)+H2O(g)K1=[CH4][H2O][CO][H2]3Reaction 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=?
D K3=1K1×1K2
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? A Q=(80.)2(10.)(2.0)>Kp and equilibrium will be approached by producing NOBrbecause the forward reaction is faster than the reverse reaction. B Q=(80.)(10.)(2.0)<Kp and equilibrium will be approached by producing NOBrbecause the forward reaction is faster than the reverse reaction. C Q=(80.)2(10.)2(2.0)<Kp and equilibrium will be approached by consuming NOBrbecause the reverse reaction is faster than the forward reaction. D Q=(80.)2(10.)2(2.0)>Kp and equilibrium will be approached by consuming NOBrbecause the reverse reaction is faster than the forward reaction.
D Q=(80.)2(10.)2(2.0)>Kp and equilibrium will be approached by consuming NOBrbecause the reverse reaction is faster than the forward reaction.
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? 2NO(g)+Br2(g)⇄2NOBr(g) Kp=(PNOBr)2(PNO)2(PBr2)=28 SubstanceInitial Partial Pressure (torr)NO10.Br22.0NOBr80.
D Q=(80.)2(10.)2(2.0)>KpQ=(80.)2(10.)2(2.0)>Kp and equilibrium will be approached by consuming NOBrNOBr because the reverse reaction is faster than the forward reaction.
2NO(g)+Cl2(g)⇄2NOCl(g)Kc=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. SpeciesConcentration (M) NO(g)0.050 Cl2(g)0.050 NOCl(g)0.50 Which of the following is true if the volume of the container is decreased by one half? A Q=100, and the reaction will proceed toward reactants. B Q=100, and the reaction will proceed toward products. C Q=1000, and the reaction will proceed toward reactants. D Q=1000, and the reaction will proceed toward products.
D Q=1000, and the reaction will proceed toward products.
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. SpeciesConcentration (M)NO(g)0.050Cl2(g)0.050NOCl(g)0.50 Which of the following is true if the volume of the container is decreased by one half?
D Q=1000Q=1000, and the reaction will proceed toward products.
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. SpeciesConcentration (M)NO(g)0.050Cl2(g)0.050NOCl(g)0.50 Which of the following is true if the volume of the container is decreased by one half? 2NO(g)+Cl2(g)⇄2NOCl(g)Kc=2000
D Q=1000Q=1000, and the reaction will proceed toward products.
Cl2(aq)+2H2O(l)⇄H3O+(aq)+Cl−(aq)+HOCl(aq) Kc=[H3O+][Cl−][HOCl]/[Cl2]=4.8×10−4 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 Qc and predicts the response by the system immediately after dilution? A Qc=4Kc, and the rate of the reverse reaction will be greater than the rate of the forward reaction. B Qc=4Kc, and the rate of the forward reaction will be greater than the rate of the reverse reaction. C Qc=Kc/4, and the rate of the reverse reaction will be greater than the rate of the forward reaction. D Qc=Kc/4, and the rate of the forward reaction will be greater than the rate of the reverse reaction.
D Qc=Kc/4, and the rate of the forward reaction will be greater than the rate of the reverse reaction.
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 Qc and predicts the response by the system immediately after dilution? Cl2(aq)+2H2O(l)⇄H3O+(aq)+Cl−(aq)+HOCl(aq) Kc=[H3O+][Cl−][HOCl][Cl2]=4.8×10−4
D Qc=Kc4Qc=Kc4, and the rate of the forward reaction will be greater than the rate of the reverse reaction.
/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 ? A S=Ksp−−−√ B S=Ksp/2−−−√ C S=Ksp/2−−−√3 D S=Ksp/4−−−√3
D S=Ksp/4−−−√3
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? Ag2CO3(s)⇄2Ag+(aq)+CO32−(aq)
D S=Ksp4−−−√3
2X(g)+Y2(g)⇄2XY(g) A reversible reaction is represented by the equation above. The amounts of reactants and products at time 1 are shown in the particle diagram on the left. The particle diagram on the right shows the amounts of reactants and products at time 2. Based on the diagrams, what can be inferred about the relative rates of the forward and reverse reactions between time 1 and time 2 ? A Nothing can be inferred because the total number of X and Y atoms is the same in each diagram. B Nothing can be inferred because the temperature of the system may have been changed. C The rate of the reverse reaction is greater than the rate of the forward reaction. D The rate of the forward reaction is greater than the rate of the reverse reaction.
D The rate of the forward reaction is greater than the rate of the reverse reaction.
A reversible reaction is represented by the equation above. The amounts of reactants and products at time 1 are shown in the particle diagram on the left. The particle diagram on the right shows the amounts of reactants and products at time 2. Based on the diagrams, what can be inferred about the relative rates of the forward and reverse reactions between time 1 and time 2? 2X(g)+Y2(g)⇄2XY(g)
D The rate of the forward reaction is greater than the rate of the reverse reaction.
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? A [N2O5]<<[NO3], because a small K value indicates that the consumption of the reactants is favored at equilibrium. B [NO2]<<[N2O5], because a small K value indicates that the consumption of the reactants is favored at equilibrium. C [NO2]<<[NO3], because a small K value indicates that the formation of products is not favored at equilibrium. D [N2O5]<<[NO2], because a small K value indicates that the formation of products is not favored at equilibrium.
D [N2O5]<<[NO2], because a small K value indicates that the formation of products is not favored at equilibrium
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?
D [N2O5]<<[NO2][N2O5]<<[NO2], because a small KK value indicates that the formation of products is not favored at equilibrium.
When AgCl(s) is placed in water, it dissolves according to the chemical equation above. The particle diagram above was proposed to represent an aqueous solution in which AgCl(s) is in equilibrium with its ions. Which of the following best explains whether or not the diagram provides a good representation of this dynamic equilibrium at the microscopic level?
D. It is not a good representation because it does not illustrate the dynamic equilibrium in which the rates of the forward and reverse reactions are equal.
A student prepared a saturated aqueous solution of Mg(OH)2 and measured its pH, as shown in Figure 1 above. Then the student added a few drops of an unknown solution to the test tube and observed cloudiness in the solutions as shown in Figure 2. On the basis of this information and the equilibrium represented above, which of the following is most likely the identity of the reagent added from the dropper?
D. KOH(aq)
Based on the information given above, which of the following is the expression for Keq for the reaction that occurs when a 0.1MAgNO3(aq) is added to a saturated solution of PbCl2(aq), as represented by the following chemical equation?
D. Keq=K1/(K2)2
The table lists the initial concentrations of each substance in the system represented by the equation above at a given temperature. Which of the following best predicts what will occur as the system approaches equilibrium?
D. The rate of the reverse reaction will be greater than the rate of the forward reaction and additional CH3OH(g) will be consumed because Kc<Qc.
In a large reaction vessel at a constant temperature, nitrogen dioxide and dinitrogen tetroxide are in a state of dynamic equilibrium, as represented by the chemical equations shown above. The equilibrium constants for the reactions are K1 and K2. Which of the following quantities can most easily be used to find the value of K2?
D. The value of K1
A 0.10mol sample of solid zinc was added to 500.0mL of 1.0M Cu(NO3)2(aq). After the mixture sits overnight, which of the following best describes what was most likely observed and measured the next morning and why?
D. Virtually all of the Zn(s) will have disappeared and Cu(s) will have appeared in the beaker, because the reaction went almost to completion at equilibrium due to the very large Keq.
The graph above represents the data collected under certain conditions for the decomposition of N2O4(g) according to the chemical equation above. Based on the graph, at approximately which time is equilibrium established?
D. At time D, because there are no observable changes in [NO2] and [N2O4].
When colorless solutions containing Fe ions and SCN ions are combined, a deep-red complex ion, FeSCN quickly forms, as shown in the net ionic equation above. Which of the following explains the observation that adding a few additional crystals of KSCN results in the red color of the solution becoming deeper?
The added KSCN dissolves, causing the reaction system to respond by producing more product to partially consume SCN and reduce its concentration.
Fe3+(aq)Colorless+ SCN−(aq)Colorless⇄ FeSCN2+(aq)RedFe3+(aq) 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 of KSCN(s) 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.
3 O2(g) ⇄ 2O3(g) Kc = 1.8 × 10−56 at 570 K For the system represented above, [O2] and [O3] initially are 0.150 mol/L and 2.5 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.
2 SO3(g) ⇄ 2 SO2(g) + O2(g) After the equilibrium represented above is established, some pure O2(g) is injected into the reaction vessel at constant temperature. After equilibrium is reestablished, which of the following has a lower value compared to its value at the original equilibrium?
The amount of SO2(g) in the reaction vessel
Two students prepared aqueous solutions of LiCl and measured the properties, as shown in the table above. Both students observed that the solid LiCl readily dissolved in H2O. The students drew particle diagrams to explain the changes in enthalpy and entropy of dissolution for LiCl based on their results and observations. Based on this information, the better particle diagram was drawn by which student, and why is that diagram more accurate?
The better particle diagram was drawn by student 1 because when LiCl dissolves in water, it dissociates into Li and Cl ion causing an increase in entropy.
A saturated aqueous solution of CdF2 is prepared. The equilibrium in the solution is represented above. In the solution, [Cd]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.
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)
At 298 K, NH4NO3 readily dissolves in water, suggesting that the change in free energy (ΔG) 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 (ΔH) and the change in entropy (ΔS). 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.
X(g)+Y(g)⇄XY(g) The particle diagram above illustrates the changes that take place when X(g) and Y(g) are placed inside a rigid container at constant temperature. Which of the following is a characteristic of a system at equilibrium that is best represented by the particle diagram?
The particle diagram shows that after 200s there are no observable changes in the amounts of reactants and products, which is a characteristic of a system at equilibrium.
Shown above is the chemical equation for the dissolution of the slightly soluble salt CuBr. Its Ksp value in pure water was experimentally determined. CuBr was found to be mush less soluble in a .001 M NaBr solution than in pure water. Which og the following correctly explains the decrease in solubility of CuBr in .001 M NaBr?
The presence of additional Br ions already in the solution means equilibrium will be reached when much less CuBr has dissolved
H2(g)+I2(g)⇄2HI(g) Hydrogen gas reacts with iodine gas at constant temperature in a sealed rigid container. The gases are allowed to reach equilibrium according to the equation above. Which of the following best describes what will happen to the reaction immediately after additional iodine gas is added to the system?
The rate of the forward reaction becomes greater than the rate of the reverse reaction.
2X(g)+Y2(g)⇄2XY(g) A reversible reaction is represented by the equation above. The amounts of reactants and products at time 1 are shown in the particle diagram on the left. The particle diagram on the right shows the amounts of reactants and products at time 2. Based on the diagrams, what can be inferred about the relative rates of the forward and reverse reactions between time 1 and time 2 ?
The rate of the forward reaction is greater than the rate of the reverse reaction.
A reversible reaction is represented by the equation above. The amounts of reactants and products at time 1 are shown in the particle diagram on the left. The particle diagram on the right shows the amounts of reactants and products at time 2. Based on the diagrams, what can be inferred about the relative rates of the forward and reverse reactions between time 1 and time 2?
The rate of the forward reaction is greater that the rate of the reverse reaction
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 equation. 3 H2(g) + N2(g) ⇄ 2 NH3(g) ΔHo = -92 kJ/molrxn The diagram below shows how the concentrations of H2 , N2 , and NH3 in this system changed over time. 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.
In an experiment X and Y 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. Based on the data, which of the following claims is most likely correct?
The reaction reached equilibrium between 75 minutes and 155 minutes after the reactants were combined because the concentrations X and XY remained constant.
X(g)+Y(g)⇄XY(g) In an experiment, X(g)X(g) and Y(g)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. Based on the data, which of the following claims is most likely correct?
The reaction reached equilibrium between 75 minutes and 155 minutes after the reactants were combined because the concentrations of X and XY remained constant.
2 XY(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. The temperature of the reaction mixture is held constant. In which direction will the reaction proceed?
The reaction will form more reactant.
Shown above is information about the dissolution of AgCl 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 attend 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 would dissolve because of the common ion effect due to the Cl 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 0.0100M. The following table shows the concentrations of the gases at equilibrium at a particular temperature. If the experiment is repeated at a higher temperature at which Kc is larger, which of the following best describes the effect of the temperature change on 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 AA and BB react in a 2-to-1 ratio.
The table above shows data for two reactions carried out in two separate evacuated 1.0-liter rigid containers at constant temperature of 298K. To each container 0.50mol 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 containers at equilibrium?
[BrCl]eq > [NO]eq because the much larger [K]eq for reaction 1 means that a much higher concentration of products will be present at equilibrium for reaction 1 compared with reaction 2.
A 2.0 mol sample of CO and a 2.0 mol sample of H2O 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]
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]
A 1.0 mol sample of CO and a 1.0 mol sample of H2 are pumped into a rigid, previously evacuated 2.0 L reaction vessel at 438 K. Which of the following is true at equilibrium?
[H2] < [CO]
CO(g) + 2 H2(g) ⇄ CH3OH(g) ΔH < 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]
A 1.0 sample of X and a 1.0 mol sample of Q 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]
X(g) + 2 Q(g) ⇄ R(g) + Z(g) Kc = 1.3 × 105 at 50°C A 1.0 mol 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]
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, KcKc, at 490K. In a second experiment done at the same temperature, [Z]eq≈1.0 M[Z]eq≈1.0 M. Which of the following is the approximate equilibrium concentration of YY 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.
2NO2(g)⇄N2O4(g)Kc=200 The equilibrium system shown above is represented in the diagram below in which each molecule represents one mole of the substance in a 100.L container at a constant temperature. Additional N2O4(g) is added to the container and allowed to reestablish equilibrium. Which of the following best represents the system after the equilibrium has been reestablished?
the one with 5 molecules
Refer to the following. 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. Additional Cl2(g) is injected into the system at equilibrium. Which of the following graphs best shows the rate of the reverse reaction as a function of time? (Assume that the time for injection and mixing of the additional Cl2(g) is negligible.)
the one with the highest spike
On the basis of the information above, the dissolution of FeF2 in acidic solution is
thermodynamically favorable, because K3 > 1
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
NH3 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 in the mixture after equilibrium is reestablished?
Adding some N2
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)
A sample of N2O4(g) is placed into an evacuated container at 373K 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?
At 60 seconds, because [NO2] and [N2O4] remain constant, indicating that the forward and reverse reaction rates are equal.
Shown above is information about the dissolution of AgCl(s) in water at 298K. 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−]=0.010M) instead of distilled water and the student did not account for the Cl− in the tap water? AgCl(s) ⇄ Ag+(aq)+Cl−(aq)Ksp=1.8×10−10
B The value obtained for KspKsp would be too small because less AgCl(s)AgCl(s) would dissolve because of the common ion effect due to the Cl−(aq)Cl−(aq) already in the water.
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, Kc, at 490K. 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? A [Y]eq≈1.4 M because [Y]eq−[Z]eq should be the same for the same reaction. B [Y]eq≈1.5 M because the ratio [Z]eq[Y]eq should remain constant when the reaction is done at the same temperature. C [Y]eq≈1.6 M because the ratio [Y]initial[Y]eq should remain constant when the reaction is done at the same temperature. D [Y]eq≈2.0 M because ([Y]initial−[Y]eq)=([Z]initial−[Z]eq) should be the same for the same reaction.
B [Y]eq≈1.5 M because the ratio [Z]eq[Y]eq should remain constant when the reaction is done at the same temperature.