Packard AP Chemistry Final Exam Semester 2
When 200 ml of 2M NaOH is added to 500ml of 1M HCl, the pH of the resulting mixture is closest to
1.0
Based on the bond energies shown in the table above, which of the following diagrams best represents the change in energy as the reaction represented below proceeds? H2 +Cl2 arrow 2HCl
190 hump is first
What is the value of the enthalpy change per mole of HCl produced?
-93K
Fe + 2 HCl arrow FeCl2 + H2 When a student adds 30ml of 1M HCl to 0.56g of powdered Fe, a reaction occurs according to the equation above. When the reaction is complete at 273K and 1 atom, which of the following is true?
0.22 L of H2 has been produced
Which of the following Lewis electron dot diagrams represents the molecule that contains the smallest bond angle?
3 - F 1- N
The students determined that the reaction produced .01 mol of CuNO3.
32%
The student wants to use the spectrophotometer to measure [C25H30N3] with the greatest sensitivity as the reaction progresses. Which of the following indicates the best wavelength setting and explains why it is best?
590nm, because only the violet form of the molecule will absorb significantly at this wavelength
A student performs an acid-base titration and plots the experimental results in the graph above. Which of the following statement best explains the experimental findings?
A weak acid was titrated with a strong base, as evidenced by the equivalence point at pH >7.
Equal volumes of 0.1M AgNO3 and 2.0 M NH3 are mixed and the reactions represented above occur. Which Ag species will have the highest concentration in the equilibrium system shown below, and why? Ag + 2NH3 arrow Ag(NH3)2
Ag(NH3)2 because Keq3 = 1.6E7
the first ionization energy of an element is the energy required to remove an electron form a gasous atom of an element
Al + Mg --> Al + Mg
Which of the following best help explain why an increase in temperature increases the rate of a chemical reaction?
At higher temps, high energy collisions happen more frequently.
The process of dissolution of NaCl in H2O is represented in the diagram above. Which of the following summarizes the sign of deltaH and deltaS for each part of the dissolution process?
Breaking solvent-solvent interactions: +,+ Breaking solute-solute interactions: +,+ Forming solute-solvent interactions: -,-
An acetate buffer solution is prepared by combining 50. mL of 0.20M acetic acid, HC2H3O2, and 50.mL of 0.20M sodium acetate, NaC2H3O2. A 5.0mL sample of 0.10M Na OH is added to the buffer solution. Which of the following is a correct pairing of the acetate species present in greater concentration and of the pH of the solution after the NaOH is added?
C2H3O2- >4.7
2 H2O2 arrow 2 H20 + O2 The equation and standard cell potential for the decomposition of H2O2 in acidic solution at 25C is given above. The reduction half reactions are: Which of the following is true for the decomposition of H2O2?
Delta G < 0 and Keq > 1
which of the following has the bonds arranged in order of decreasing polarity
H-F>N-F>F-F
A 0.10 mol sample of each of the four species in the reaction represented above is injected into a rigid, previously evacuated 1L container. Which of the following species will have the high concentration when the system reaches equilibrium?
H2S
Two molecules of the amino acid glycine join through the formation of a peptide bond, as shown above. The thermodynamic data for the reaction are listed in the following table.
It is not favored at any temperature.
Which of the following statements about the thermodynamic favorability of the reaction at 298 K is correct?
It is thermodynamically favorable and is driven by Delta H only.
2 BaO2 arrow 2 BaO + O2 A sealed rigid vessel contains BaO2 in equilibrium with BaO and O2 as represented by the equation above. Which of the following changes will increase the amount of BaO2 in the vessel?
Lowering the temperature
On the basis of molecular structure and bond polarity, which of the following compounds is most likely to have the greatest solubility in water?
NH3
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?
O3 +NO arrow NO2 +O2: Slow NO2 +O arrow NO + O2: Fast
A 1.0L solution of AgNO3 and Pb(NO3)2 has a Ag concentration of 0.020M and a Pb concentration of 0.001M. A 0.001 mol sample K2SO4 is added to the solution. Based on the information in the table above, which of the following will occur?
Only PbSO4 will percipitate
The reaction between NO2 and CO is represented above. The elementary steps of a proposed mechanism are represented below: Which of the following is the rate law for the overall reaction is consistent with the proposed mechanism?
Rate = k[NO2]2
Based on the information above and periodic trends, which of the following is the best hypothesis regarding the oxide formed by Rb?
Rb will form Rb2O, Rb2O2, and RbO2
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 1.0L to 0.5L at constant temperature, for which of the reactions will the amount of products be increased?
Reaction A
The equilibrium system represented by the equation above initially contains equal concentration fo Cr2O7 2- and CrO4 2-. Which of the following statements correctly predicts the result of adding a sample of 6.0M NaOH to the system and provides an explanation?
The mixture will become more yellow because OH- will shift the equilibrium toward products
When H2 and O2 are mixed together in a rigid reaction vessel at 25C, 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 gases are originally at 25C?
The reaction has a large activation energy at 25C
CH3OH arrow CO +2 H2 The reaction represented above goes essentially to completion. The reaction takes place in a rigid , insulated vessel that is initially at 600k Which of the following statement about the bonds in the reactants and products in most accurate?
The sum of the bonds enthalpies of the bonds in the reactant is greater than the sum of the bond enthalpies of the bonds in the products.
Which of the following changes will most likely increase the rate of reaction between Li(s) and water?
Using a 0.35g sample of Li(s) cut into small pieces.
A student prepares a solution by combing 100mL of 0.30 M HNO2 and 100mL of 0.30 M KNO2. Which of the following equations represents the reaction that best helps to explain why adding a few drops of 1.0M HCL does not significantly change the pH of the solution?
(H+) + (NO2) arrow HNO2
2 H2O2 arrow 2 H20 + O2 The equation and standard cell potential for the decomposition of H2O2 in acidic solution at 25C is given above. The reduction half reactions are: What is the standard reduction potential for the half reaction represented above?
+0.68V
Based on the formation in the table above, which of the following shows the cell potential and Gibbs free energy change for the overall reaction that occurs in a standard galvanic cell?
+1.63; -944
If P(N2O4) is 1.33 atm when the system is at equilibrium at 70C, which is P(NO2)?
2.0atm
Based on the bond energies listed in the table above, which of the following is closest to the bond energy of C-N bond?
300 kJ/ mol
Which of the following molecules is least soluble in water?
4 Cl and 1 C atom
If the absorbance of the mixture is .2 at 453 nm how many moles of fe were present in the 100 ml sample
4x10^_6
On the basis of pH curve, the pKa value of the acid is closest to
5
ClO2 +HCOOH arrow HClO2 + HCOO What are the relative strengths of the acids and bases in the reaction by the equation above?
Acid Strength: HClO2 > HCOOH Base Strength: ClO2 < HCOO
NH3 was synthesized at 200C in the presence of a powdered Os(s) catalyst, leading to equilibrium system represented above. Which of the following changes would result in more NH3 in the mixture after equilibrium is reestablished?
Adding some N2 (g)
The oH of a 0.01 M HNO2 solution is in which of the following ranges? (For HNO2, Ka = 4E-4)
Between 2 and 3
a 23.0g sample compound contains 12.0 of C, 3.0g of H, and 8.0g of O. Which of the following is the empirical formula of the compound?
C2H6O
The compound CCl4 is nonflammable and was once commonly used in fire extinguishers. On the basis of periodic properties, which of the following compounds can most likely be used as a fire-resistant chemical?
CBr4
In which of the following liquids do the intermolecular forces include dipole-dipole forces?
CH2F2
On the basis of the information above, which of the following arranged the binary compounds in order of increasing bond polarity?
CH4<SiCl4< SF4
Based on the information in the table above, which liquid, CS2 or CCl4, has the higher equilibrium vapor pressure at 25C, and why?
CS2, because it has waker LDF
Which of the following best helps to explain why the value of Delta H for the dissolving of CaF2 in water is positive?
Ca ions have a very strong ion-ion interactions with F in the crystal lattice
Which of the following represents a reaction for which the standard entropy change is positive?
CaCO3 arrow CaO + CO2
A solution containing HCl and the weak acid HClO2 has a pH of 2.4. Enough KOH is added to the solution to increase the pH to 10.5. The amount of which of the following species increases as the KOH is added?
ClO2
At 1 atm a sample of ice is heated to liquid water and then to water vapor. The heating curve is shown in the graph above. Which of the following lists the signs of the changes in enthalpy and entropy for the process corresponding to segment X, going left to right?
Delta H: Positive Delta S: Positive
the complete photo electron spectra of neutral atoms of two unknown elements, X and Y are shown above. Which of the following can be inferred from the data
Element Y has a greater nuclear charge when element X does
Which of the following arranges the molecules N2, O2, and F2 in order of their bond enthalpies, from least to greatest?
F2<O2<N2
CO + 2 H2 arrow CH3OH The synthesis of CH3OH from CO andH2 is represented by the equation above. The value of Kc for the reaction at 483 K is 14.5 A mixture of CO and H2 is pumped into a previously evacuated 2L reaction vessel. The total pressure of the system is 1.2 atm at equilibrium. What will be the total pressure of the system if the volume of the reaction vessel is reduced to 1L at constant temperature?
Greater than 1.2 atm but less than 2.4 atm
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? From top to bottom and left to right
H - F H-N-B-F H-F
Which of the substances listed above has the highest boiling point, and why?
HF, because its molecule form hydrogen bonds
HX + Y arrow HY + X Keq >1 Based on the information given above, which of the following is the strongest acid?
HX(aq)
A sample of a hard, solid binary compound at room temperature did not conduct electricity as a pure solid but became conductive when dissolved in water. Which of the following types of interactions is most likely found between the particles in the substance?
Ionic bonds
Each student in a class is placed a 2 g sample of a mixture of CU and AL in fume hood. The students slowly poured15 ml of 15.8M HNO3 into their beakers
It is a redox reaction, because CU is oxidized and the nitrogen atom in NO3 is reduced
What would be the effect on the reaction rate if the solution of C25H30N3 is diluted by a factor of two?
It would be lower
Atoms of which elements are reduced in the reaction?
O in Na2O2; each atom gain one electron
Based on the Ksp values in the table above, a saturated solution of which of the following compounds has the highest[ Cl-]?
PbCl2
What will be the effect on the amount of gas produced if the experiment is repeated using 0.35g of K(s) instead of 0.35g of Li(s)?
Some gas will be produced but less than the amount of gas produced with Li(s).
A vessel contains Ar at a high pressure. Which of the following statements best helps to explain why the measured pressure is significantly greater than the pressure calculated using the ideal gas law?
The combined volume of the Ar atoms is too large to be negligible compared with the total volume of the container.
Benzene, C6H6, has the structure above. Considering the observation that benzene is only sparingly soluble in water, which of the following best described the intermolecular forces of attraction between water and benzene?
There are dipole- included dipole and London dispersion interactions between water and benzene.
NaOH + HCl arrow NaCl +H2O To determine the concentration of a NaOH solution, a student titrated a 50.mL with 0.10M HCl. The reaction is represented by the equation above. The titration is monitored using a pH meter, and the experimental results are plotted in the graph to the right. A student conducted an experiment to determine delta Hrxn for the reaction between HCl and NaOH. The student ran two trials using the volumes of HCl and NaOH indicated in the table above, and determined the amount of heat released. Which of the following best explains the relationship between X and Y?
Y=X, because the number of moles of acid and based reacting with each other is the same in both trials.
Table of X,Y,Z Which of the following correctly ranks the three monoprotic acids listed in the table above from the weakest to the strongest?
Z<Y<X
A mixture of CO and O is placed in a container, as shown above. A reaction occurs, forming CO2. Which of the following best represents the contents of the box after the reaction has proceeded as completely as possible
[4-3 molecule, 1-2 molecule]
In the reaction represented above, what is the hybridization of the C atoms beofre and after the reaction occurs
before sp^2 after sp^3
Based on structures shown above, which of the following statements identifies the compound with the higher boiling point and provides the best explanation for the higher boiling point
compound 2, because it forms hydrogen bonds, whereas compound 1 does not
The exothermic dissolution of Mg(OH)2 in water is represented by the equation above. The KSP of Mg(OH)2 is 1.8E-11. Which of the following changed will increase the solubility of Mg(OH)2 in an aq solution?
decreasing the pH
at 298k and 1 atm, Br2 is a liquid with a high vapor pressure, and Cl2 is a gas
forces among Br2 molecules are stronger than those among Cl2
A student is given a sample of a pure, white crystalline substance. Which f the following would be most useful in providing data at determine if the substance is an ionic compound
testing the electrical conductivity of an aqueous solution of the substance
IN one student's experiment the reaction proceeded at a much slower rate than it did in the other student's experiments
the student used a 1.5M solution of HNO3 instead of 15.8 solution of HNO3
NaOH + HCl arrow NaCl +H2O To determine the concentration of a NaOH solution, a student titrated a 50.mL with 0.10M HCl. The reaction is represented by the equation above. The titration is monitored using a pH meter, and the experimental results are plotted in the graph to the right. A student mixes a 10ml sample of 1.0 M NaOH with a 10.0ml sample of 1.0 M HCl in a polystyrene container. The temperature of the solutions before mixing was 20C. If the final temperature of the mixture is 26C, what is the experimental value of Delta Hrxn?
-50.kJ/molrxn
Based on the thermodynamic data, which of the following is true at 298K?
0<KEQ<1
Which of the following is the balanced net ionic equation for the reaction between Li(s) and water?
2 Li +2 H20 arrow 2 Li (aq) + 2OH (aq) + H2 (g)
When 4 L of He, 6 L of N2 and 10 L of Ar, all at 0 C and 1 atm, are pumped into an evacuated 8 L rigid container, the final pressure in the container at 0 is
2.5 atm
When 5.0g of NH4ClO4 is added to 100 mL of water in a calorimeter, the temperature of the solution formed decreases by 3C. If 5.0g of NH4ClO4 i is added to 1000mL of water in a calorimeter initially at 25C, the final temperature of the solution will be approx.
24.7C
CH3OH arrow CO +2 H2 The reaction represented above goes essentially to completion. The reaction takes place in a rigid , insulated vessel that is initially at 600k A sample of CH3OH is placed in the previously evacuated vessel with a pressure of P1 at 600K. What is the final pressure in the vessel after the reaction is complete and the contents of the vessel are returned to 600K?
3 P1
Approximately how long did it take for 75 percent of the initial amounT of C25H30N3 to react?
300s
A particle view of a sample of H2O2 is shown to the right. The H2O2 is titrated with KMnO4, as represented by the equation down below. Which of the following particle views best represents the mixture when the titration is halfway to the equivalence point?
5 H2O2 particles 2 Mn2+ particles
C2H4 + H2 arrow C2H6 Which of the following will most likely increase the rate of reaction represented above?
Adding a heterogenous catalyst to the reaction system.
The photoelectron spectra of the 1s electrons of two isoelectronic species, Ca and Ar, are shown above. Which of the following correctly identifies the species associated with peak X and provides a valid justification?
Ca, because its nucleus has two more protons than the nucleus of Ar has
2 H2O2 (l) arrow 2 H2O (l) + O2 (g) The exothermic process represented above is best classified as a
Chemical change because covalent bonds are broken and new covalent bonds are formed
Which of the following statements about Delta H for the reaction is correct?
Delta H > 0 because energy is required to break the N-N bond.
A mixture containing equal numbers of moles ethyl acetate and butyl acetate was separated using distillation. Based on the diagrams shown above, which of the following identifies the substance that would be initially present in higher concentration in the distillate and correctly explains why that occurs?
Ethyl acetate, because it has a shorter carbon chain and weaker LDFs.
The distribution of speeds of H2 molecules at 273K and 1 atm is shown in the diagram above. Which of the following best shows the speed distribution of He(g) atoms under the same conditions of temperature and pressure?
High hump and them small hump
Which of the following is the strongest type of interaction that occurs between atoms within the circled areas of the two molecules represented above?
Hydrogen Bond
CH3OH arrow CO +2 H2 The reaction represented above goes essentially to completion. The reaction takes place in a rigid , insulated vessel that is initially at 600k What can be inferred about Delta S for the reaction at 600k?
It must be positive, since Delta G is negative and Delta H is positive.
Based on the information above, which of the following expressions represents the equilibrium constant, K, for the reaction represented by the equation below? (La3+) + CO3 arrow LaCO3+
K= (K1)(Kw)/(Ka)
CO + 2 H2 arrow CH3OH The synthesis of CH3OH from CO andH2 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 increase at 650K?
Kc will decrease because the reaction is exothermic
based on the diagram above, which of the following best helps to explain why MgO is not able to conduct electricity, but MgO is a good conductor of electricity
MgO consists of separate Mg ions and O ions held in a fixed lattice, but in MgO the ions are free to move and conduct electricity
2 NO2 +F2 arrow 2 NO2F The rate law for the reaction represented by the equation above is rate = k[NO2][F2]/ Which of the following could be the first elementary step of a two step mechanism for the reaction if the first step is slow and the second step is fast?
NO2 + F2 arrow NO2F+ F
NaOH + HCl arrow NaCl +H2O To determine the concentration of a NaOH solution, a student titrated a 50.mL with 0.10M HCl. The reaction is represented by the equation above. The titration is monitored using a pH meter, and the experimental results are plotted in the graph to the right. At the point labeled R on the pH curve, which of the following ions are present in the reaction mixture at a concentration greater than 0.01M?
Na and Cl only
Based on Coulomb's law and the information in the table above, which of the following cations is most likely to have the weakest interaction with an adjacent water molecule in an aqueous solution?
Na+
Two trials are run, using excess water. In the first trial, 7.8g of Na2O2 is mixed with 3.2g of S. In the second trial 7.8g of Na2O2 is mixed with 6.4g S. The Na2Os and S react as completely as possible. Both trials yield the same of SO2. Which of the following identifies the limiting reactant and the heat released, q, for the two trials at 298K?
Na2O2 -- 30kJ
Which of the following could be the identity of the white crystalline solid that exhibits the following properties? It melts at 320C It does not conduct electricity as a solid It conducts electricity in an aqueous solution
NaOH (s)
Which of the following best predicts how the partial pressures of the reacting species will be affected if a small amount of Ar(g) is added to the equilibrium mixture at constant volume?
No change will take place.
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
Acid dissociation constants of two acids are listed in the table above. A 20mL sample of 0.10M solution of each acid is titrated to the equivalence point with 20 mL of 0.10 M NaOH. Which of the following is a true statement about the pH of the solutions at the equivalence point?
Solution 1 has a higher pH at the equivalence point because CH3CO2H has a stronger conjugate base.
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 carbon 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 570K?
The amount of 03(g) will decrease, because Q>Kc
For element X represented above, which of the following is most likely explanation for the large difference between the second or third ionization energies?
The electron removed during the third ionization is, on average, much closer to the nucleus than the first electrons removed were.
CO + 2 H2 arrow CH3OH The synthesis of CH3OH from CO andH2 is represented by the equation above. The value of Kc for the reaction at 483 K is 14.5 Which of the following statements is true about bond energies in this reaction?
The energy absorbed as the bonds in the reactants are broken is less than the energy released as the bonds in the product are formed.
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 the [H+] at constant temperature have on the reaction represented above?
The frequency of collisions between H+ ions and ClO- ions will increase.
NaOH + HCl arrow NaCl +H2O To determine the concentration of a NaOH solution, a student titrated a 50.mL with 0.10M HCl. The reaction is represented by the equation above. The titration is monitored using a pH meter, and the experimental results are plotted in the graph to the right. One student titrated the NaOH with 1.0 M HCl instead of 0.10 M HCl. How would the student's titration curve differ from the original curve?
The pH beyond the equivalence point would be lower than in the original curve.
A student perform an analysis to determine the amount of AgNO3. Excess NaCl was added to the solution, and the Ag precipitated as AgCL. The precipitate was collected by gravity filtration and dried in an oven. Three trials were performed, and in each case, according to the instructor, the mass of precipitate recovered was 5 percent higher than the actual mass of AgCl that should have formed. Which of the following could account for that error?
The precipitate was not rinsed with deionized water before drying.
Two samples of Mg(s) of equal mass were placed in equal amounts of HCl contained in two separate reaction vessels. Particle representations of the mixing of Mg(s) and HCl (aq) in the two reaction vessels are shown in Figure 1 and Figure 2 above. Water molecules are not included in the particle representations. Which of the reactions will initially proceed faster, and why?
The reaction in Figure 2, because more Mg atoms are exposed to HCl in Figure 2 than Figure 1
A certain gas, XY, decomposed as represented by the equation above. A sample of each of the three gases is out 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.
CH3OH arrow CO +2 H2 The reaction represented above goes essentially to completion. The reaction takes place in a rigid , insulated vessel that is initially at 600k What happens to the temperature of the contents of the vessel as the reaction occurs?
The temperature must decrease the reaction is endothermic.
HCl (g) can be synthesized from H2 and Cl2 as represented above. A student studying the kinetics of the reaction proposes the following mechanism. Which of the following statements identifies the greatest single reason that the value of Kp for the overall reaction at 298K has such a large magnitude?
The value of Delta H for the overall reaction is large and negative.
Three saturated solutions (X,Y,Z) are prepared at 25C. Based on the information in the table above, which of the following lists the solutions in order of increasing [Ag+]?
Z<X<Y
A 2.0 mol sample CO and 2.0 mol sample of H2O are introduced into a perviously evacuated 100. L rigid container, and the temperature is held constant as the reaction represented above reaches equilibrium. Which of the following is true at equilibrium?
[CO2]>[CO]
CO + 2 H2 arrow CH3OH The synthesis of CH3OH from CO andH2 is represented by the equation above. The value of Kc for the reaction at 483 K is 14.5 A 1mol sample of CO and 1 mol sample H2 are pumped into a rigid, previously evacuated 2L reaction vessel at 438K. Which of the following is true at equilibrium?
[H2] < [CO]
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
the sample contains NaCl and LiCl
To determine the number of moles of Cu in the sample of the mixture, the students measured the absorbance of known concentrations of CuNO3 using a spectrophotometer
the student labelled the cuvettes incorrectly, reversing the labels of the solutions of known concentrations
At room temperature 12 is a molecular solid. Which of the following provides a characteristic of I2 with a correct explanation?
It is not a good conductor of electricity because its valence electrons are localized in bonding and nonbonding pairs