2AP Chemistry Possible Questions Bank
Compared to the equilibrium vapor pressure of CH3OH at 300 K, the equilibrium vapor pressure of C2H5OH at 300 K is
lower, because LDFs among C2H5OH molecules are greater than those among the CH3OH
On the basis of the information above, the dissolution of FeF2 in acidic solution is
thermodynamically favorable, because K3 > 1
What is the value of the enthalpy change per mole of HCl produced?
-93 kJ
The temperature of the CH3OH is increased from 300 K to 400 K to vaporize all the liquid, which increases the pressure in the vessel to 0.30 atm. The experiment is repeated under identical conditions but this time using half the mass of CH3OH that was originally used. What will the pressure be in the vessel at 400 K?
0.15 atm
The value of Kp for the evaporation of CH3OH at 300 K is closest to
0.2
The students determined that the reaction produced .01 mol of CuNO3. Based on the measurement, what was the percent of Cu by mass in the original 2.00 g sample of the mixture? 16% 32% 64% 96%
32%
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
The reactions represented above are carried out in sealed, rigid containers and allowed to reach equilibrium. If the volume of each container is reduced from 1.0 L to 0.5L at constant temperature, for which of the reactions will the amount of product(s) be increased?
A
When a small amount of 12M HNO3 is added to a buffer solution made by mixing CH3NH2 and CH3NH3Cl, the pH of the buffer solution changes from 10.64 to 10.62. Which of the following equations represents the reaction that accounts for the fact that the pH does not change significantly when the HNO3 is added?
A
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
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.
Which of the following best describes the change that takes place immediately after the CH3OH(l) is introduced into the previously evacuated vessel?
A physical change takes place because intermolecular attractions are overcome
A sealed rigid vessel contains Bao2(s) in equilibrium with BaO(s) and 02(g) as represented by the equation above. which of the following changes will increase the amount of Ba02(s) in the vessel?
A. adding a small amount of o2(g)
Based on the data above, What is the value of delta g for this reaction
A. delta g<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?
Adding NaF(s), because the reaction will proceed to the reactants
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
The first ionization energy of an element is the energy required to remove an electron from a gaseous atom of the element. The values of the first ionization energies for the third-row elements are shown in the graph above. On the basis of the information given, which of the following reactions is exothermic?
Al(g) + Mg+(g) --> Al+(g) + Mg(g)
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 decomposition of O3 in the upper atmosphere is represented by the equation above. The potential energy diagram for the decomposition of O3 in the presence and absence of NO is given below. Which of the following mechanisms for the catalyzed reaction is consistent with the equation and diagram above?
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
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.
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).
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.
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.
Based on the information in the table above, which of the following shows the cell potential and the Gibbs free energy change for the overall reaction that occurs in a standard galvanic cell?
B (+1.63,-944)
Which of the following Lewis electron-dot diagrams represents the molecule is the most polar?
B (Br-F)
The reaction mixture represented below is at equilibrium at 298 K, and the molar concentrations are [X]=1.0 molar,[y]=5.0 molar and [z]= 5.0 molar. what is the value of the eqilibrium constant for the reaction at 298 k?
B. 5.0
At 450c, 2.0 moles each of H2(g), I2(g), and HI(g) are combined in in a 1.0L rigid container. The value of Kc at 450 is 50. Which of the following will occur as the system moves toward equilibrium?
B. More HI(g) will form
At 1 mol sample of C0(g) and a 1 mol sample of H2(g) are pumped into a rigid, previously evacuation 2L reaction vessel at 483K. which of the following is true at equilibrium
B. [H2] < [CO]
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.
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.
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?
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.
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).
Which of the following explains the effect on the equilibrium constant,Kc, when the temperature of the reaction system is increased to 650K?
C. Kc will decrease because the reaction is exothermic
Which of the following statements are true about bond energies in this reaction?
C. The energy absorbed as the bonds on the reactants are broken is less than the energy released as the bonds in the product are formed.
at a certain point in time, a 1.00 L rigid reaction vessel contains 1.5 mol of pcl3(g), 1.0 mole 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?
C. the pressure will decrease because Q<Kc
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
A student prepares a soution by combining 100 mL of 0.30 M HNO2 and 100 mL pf 0.30 M KNO3. Which of the following equations represents the reaction that best helps to explain why adding a few drops of 1.0 M HCl does not significantly change the pH of the solution?
D
NH3 reacts with BF3 to form a single species. Which of the following structural diagrams is the most likely representation of the product of the reaction?
D
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 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.
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? 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.
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.
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.
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
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.
For which of the following reaction mixtures at equilibrium would reducng the volume of the container at constant temperature cause the equilibrium to shift towards the products?
D. 2No2(g) - N2O4(g)
At 25c, the equilibrium constant (kc) for the reaction represented above has the value of 1.3. At 50c, the value of the equilibrium constant is less than 1.3. based on this information, which of the following must be correct?
D. At 25c, Delata H for the reaction is negative
The reaction system represented above is a equilibrium. Which of the following will decrease the amount of CaO(s) in the system
D. Removing some CaCo3(s) at constant pressure
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
Which of the following statements about delta H for the reaction is correct?
Delta H > 0 becuase energy is required to break the N-N bond
Which of the following has the bonds arranged in the order of decreasing polarity?
H-F > N-F > F-F
Which of the substances listed above has the highest boiling point, and why?
HF, because its molecules form hydrogen bonds
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.
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
Equimolar samples of Pb(OH)2m PbI2, and PbF2 are placed in three seperate beakers, each containing 250 mL of water at 25 C. After the solutions are stirred, solid remains at the bottom of the beaker. Based on the Ksp values for the compounds listed above, a solution of which of the following compounds will have the lowest [Pb2+]
Pb(OH)2
based on the Ksp values in the table above, a saturated solution of which of the following compounds has the highest [Cl]?
PbCl2
Based on the information in the table above, which of the compounds has the highest boiling point, and why?
Propanoic acid, because it can form intermolecular hydrogen bonds
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
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
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
The step-wise dissociation of selenious acid is represented by the equations above. Which of the following best helps explain why the value of Ka2 is so much smaller than Ka1?
Removing the first H+ from H2SeO3(aq) requires less energy than removing the second H+, because the second H+ is removed from a negatively charged species.
Based on Coulomb's Law and the information in the table above, which of the following anions is most likely to have the strongest interactions with nearby water molecules in an aqueous solution?
S2-
If a pure sample of an oxide of sulfur contains 40 percent sulfur and 60 percent oxygen by mass, then the empirical formula of the oxide is
SO3
The mass of the Cu(s) produced in step 3 was slightly more than the mass predicted from the 3.8 g Cu3(PO4)2 recovered from step 1. Which of the following could account for the discrepancy in the yield of Cu from step 3?
Some unreacted Zn was mixed in with the Cu
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.
The table above provides some information about two types of steel, both of which are alloys of iron and carbon. Which of the following best helps to explain why high-carbon steel is more rigid than low-carbon steel?
The additional carob atoms within the alloy make it more difficult for the iron atoms to slide past one another
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 will decrease because Q > Kc
Which of the following correctly compares periodic properties of two elements and provides an accurate explanation for that difference?
The atomic radius of Cl is smaller than that of S because Cl has a larger nuclear charge than S does
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.
Which of the following statements best helps to explain why the contents of the tube containing the equilibrium mixture turned a lighter color when the tube was placed into an ice bath?
The forward reaction is endothermic
What effect will increasing [H+] at constant temperature have on the reaction represented above?
The frequency of collisions between H+(aq) ions and ClO-(aq) ions will increase
The equilibrium system represented by the equation above initially contains equal concentrations of Cr2O72- and CrO42-. Which of the following statements correctly predicts the result of adding a sample of 6.0 M NaOH to the system and provides an explanation?
The mixture will become more yellow because OH- will shift the equilibrium toward products
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.
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
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
When H2 and O2 are mixed together in a rigid reaction vessel at 25 C, no reaction occurs. When the mixture is sparked, however, the gases react vigorously according to the equation above, releasing heat. Which of the following statements correctly explains why the spark is needed for the reaction to occur when the gasses are originally at 25C?
The reaction has a large activation energy at 25 C
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.
A sample of a solid labeled as NaCl may be impure. a student analyzes the sample and determines that it contains 75 percent chlorine by mass. Pure NaCl contains 61 percent chlorine by mass. Which of the following statements is consistent with the data?
The sample contains NaCl(s) and LiCl(s)
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
The ionization energies of an unknown element, X, are listed in the table above. Which of the following is the most likely empirical formula of a compound formed from element X and phosphorus, P?
X3P2
The mass spectrum of an average sample of a pure element is shown in the figure above. Which of the following is the identity of the element?
Zr
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 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]
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]
