Packard AP Chemistry Final Exam Semester 2
The students determined that the reaction produced .01 mol of CuNO3. 16% 32% 64% 96%
32%
A sample of CH3OH is placed in the previously evacuated vessel witha 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
3P1
the reactions above are carried out in sealed rigid containers and allowed to reach equilibrium. if the volume of the container is reduced from 1 L to .5 L at constant temperature, for which of the reactions will the amount of products be increased
4HCL + O2 --> 2 Cl2 + 2H2O
on the basis of the pH curve, the pKa value of the acid is closest to
5
for element X represented above, which of the following is the most likely explanation for the large difference between the second and third ionization energies
the electron removed during the third ionization is, on average, much closer to the nucleus than the first electrons removed were
based on the thermodynamic data, which of the following is true at 298 K
0<k<1
When 200ml of 2M NaOH is added to 500ml of 1M HCl, the pH of the
1
what is the standard reduction potential for the half reaction represented above?
+.68 V
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
approximately how long did it take for 75 percent of the inital amount of C25H30N3 to react?
200s
which of the following has the bonds arranged in order of decreasing polarity H-F>N-F>F-F H-I>H-Br>H-F O-N>O-S>O-Te Sb-I> Sb-Te>Sb-Cl
H-F>N-F>F-F
Based on the information given above, which of the following is the strongest acid
Hx
A sealed ridig 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
Which of the following Lewis elctron dot diagrams representes the molecule that contains the small bond angle?
N connected to 3 F
A 1 L solution of AgNO3 and Pb(NO3)2 has a Ag concentration of .02 M and a PB concentration of .001M a .001 mol sample of K2SO4 is added to the solution. based on the information in the table above, which of the following will occur?
Only PbSO4 will precipitate
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 Rb2O2 and RbO2
Which of the following will most likely increase the rate of the reaction represented above?
adding a heterogenous catalyst to the reaction system.
What happens to the temperature of the contents of the vessel as the reaction occurs
the temperature must decrease, because the reaction is endothermic
a student mixes a 10 ml sample of 1M Naoh with a 10 ml sample of 1M HCl in a polystyrene container. The temperature of the solutions before mixing was 20 C. If the final temperature of the mixture is 26C what is the experimental value of Hrxn
-50 kL/mol
What is the value of the enthalpy change per mole of HCl produced
-93 kJ
When a student adds 30mL of 1 M HCl to .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?
.22L of H2 has been produced
if P(N2O4) is 1.33 atm when the system is at equilibrium at 70 C which is P(NO2)
2 atm
When 5 g of NH4ClO4 is added to 100 ml of water in a calorimiter, the temperature of teh solution formed decreases by 3 C. if 5 g of NH4ClO4 is added to 1000 mL of water in a calorimeter initially at 25 C, the final temperature of the solution will be approximately
24.7 C
which of the following is the balanced net ionic equation for the reaction between Li and water
2Li +2H2O --> 2Li+2OH+H2
An acetate buffer solution is prepared by combining 50 mL of .2M acetic acid, HC2H3O# and 50 Ml of .2 M sodium acetate, NaC2H3O2. a 5 mL sample of .1 M NaOH 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?
Acetate species: C2H3O2 pH: >4.7
What re the relaative strengths of the acids and bases in the reaction represented by the equation above?
Acid Strength: HClO2>HCOOH Base Strength: CLO2<HCOO
equal volumes of .1 M AgNO3 and 2M NH3 are mixed and ther eactions represented above accur. which AG species will have the highest concentration in the equilibrium system shown below, and why?
Ag(NH3)2 because Keq3 = 1.6x10^7
the first ionization energy of an element is the energy required to remove an electron form a gaseous atom of an element Cl+Mg-->Cl+Mg Al+Mg-->Al+Mg P+Mg-->P+Mg S+Mg-->S+Mg
Al + Mg --> Al + Mg
Which of the following represents a reaction for which teh standard entropy change is positive?
CaCo3 --> CaO + CO2
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
A student prepares a solution by combining 100 ml of .3 M HNO2 and 100 Ml of .3 M. Which of the following equations represents the reaction that best helps to explain why adding a few drops of 1 M HCl does not significantly change the pH of the solution
H + NO2 --> HNO2
Based on the information above, which of the following expressions represents the equilibrium constant, K for the reaction represented by the equation below?
K=(K1)(Kw)/Ka
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 does not contain free electron, but MgO contains free elctrons that can flow MgO contains no water, but MgO contains water that can conduct electricity MgO consists of separate Mg ions and O ions but MgO contains MgO molecules that can conduct electricity MgO consists of separate mg ions and O ions held in a fixed lattice, but in MgO the ions are free to come and consuct 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
The ideal gas law best describes the properties of which of the following gases PH3 HBr SO2 N2
N2
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 rate law for the reaction 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 --> NO2F + F
Atoms of which element are reduced in the reaction?
O in Na2O2; each atom gains 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
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
one student titrated the NaOH with 1 M HCl instead of .1M HCl. How would the student's titration curve differ from the original curve
The pH far beyond the equivalence point would be lower than in the original curve
Which of the following correctly ranks the three monoprotic acids listen in the table above from the weakest to the strongest?
Z<Y<X
The mass spectrum of an average sample of a pure element is shown in the figure above Y Zr Nb Th
Zr
a student performs an acid-base titration and plots the experimental results in the graph above. Which of the following statements best explains the experimental findings
a weak acid was titrated with a strong base, as evidenced by the equivalence point at pH>7
Which of the following best help explain why an increase in temperature increases the rate of a chemical reaction
at higher temperatures, high energy collisions happen more frequently
Which of the following is the strongest type of interaction that occurs between the atoms within the circled areas of the two molecules represented above?
hydrogen bond
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 blow proceeds
reactants start at 190
the distribution of speeds of h2 molecules at 273 K and 1 atm is shown in the diagram above. Which of the following best shows the speed distribution of He atoms under the same conditions of temperature and pressure
smaller solid curve, taller dotted line with curve on left
what will be the effect on the amount of gas produced if the experiment is repeated using .35g of K instead of .35 g of Li
some gas will be produced but less than the amount of gas produced with Li
what effect will increasing H at constant temperature have on the reaction represented above?
the frequency of collision between H ions and CLo ions will increase
The equilibrium system represented by the equation above initially contains equal concentrations of Cr2O7 and CrO4. Which of the folloinf statements correctly predicts the result of adding a sample of 6M NaOH to the system, and provides an explanation
the mixture will become more yellow because Oh will shift the equilibrium toward products
the temperature of the reaction mixture is help constant. In which direction will the reaction proceed
the reaction will form more reactant
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
IN one student's experiment the reaction proceeded at a much slower rate than it did in the other student's experiments in the student's sample the metal pieces were much smaller than those in the other student's samples the student heated the reaction mixture as the HNO3 was added the student used a 1.5M solution of HNO3 instead of 15.8 solution of HNO3 the student used a 3 g sample of the mixture instead of the 2 g sample that was used by the other students
the student used a 1.5M solution of HNO3 instead of 15.8 solution of HNO3
Which of the following statement about the bonds in the reactants and products is most accurate
the sum of the bond 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 statements identifies the greatest single reason that the value of Kp for the overall reaction 298 k has such a large magnitude
the value of H for the overall reaction is large and negative
which of the following changes will most likely increase the rate of reaction between Li and water
using a .35g sample of Li cut into small pieces
Which of the following molecules is least soluble in water
C ions connected to 4 Cl ions
a 23 g sample of a compound contains 12 of C, 3 g of H and 8g 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 arranges the binary compounds in order of increasing bond polarity
CH4<SiCl4<SF4
a 2 mol sampleof Co and 2 mol ampleof H2O are introduced into a preciously evacuated 100L rigid container, and the temperature is held constant as the reaction represented above reaches equilibrium. Which of the following is true at equilbrium
CO2>CO
based on the information in the table above, which liquid, CS2 of CCl4 has the higher equilibrium vapor pressure at 25 C and why?
CS2, because it was weaker London dispersion forces
Which of the following best helps to explain why the value of H for the dissolving CaF2 in water is positive?
Ca ions have very strong ion-ion interactions with F in the crystal lattics
A solution containing HCl an 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
based on the information 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
Ecell = 1.63, G = -944
Which of the substances listed above has the highest boiling point, and why?
HF, because its molecule form hydrogen bonds
At the point label R on the pH curve, which of the following ions are present in the reaction mixture at a concentration greater than .01 M
Na and Cl only
Which of the following could be the identity of a white crystalline solid that exhibits the following properties?
NaOH
a student conducted an experiment to determine Hrxn for the reaction between HCl and NaOH. the studnet 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
three saturated solution are prepared at 25 C based on the information in teh table above, which of the following lists the solutions in order of increasing Ag
Z<X<Y
NH3 was synthesized at 200 C in the presence of a powdered O2 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
In the reaction represented above, what is the hybridization of the C atoms before and after the reaction occurs before sp after sp^2 before sp after sp^3 before sp^2 after sp before sp^2 after sp^3
before sp^2 after sp^3
The pH of a .01M HNO2 solution is in which of the following ranges?
between 2 and 3
the exothermic process represetned above is best classifies as a
chemical change because covalent bonds are broken and new covalent bonds are formed
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 1.8x10^-11. Which of the following changes will increase the solubility of Mg(OH)2 is an aqueous solution
decreasing the pH
A mixture containing equal numbers of moles of 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 London dispersion forces
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 forces among Cl2 molecules are stronger than the Cl-Cl bonds Br-Br bond is stronger than the Cl-Cl bond Cl-Cl bond is stronger than the Br-Br bond
forces among Br2 molecules are stronger than those among Cl2 molecules
At room temperature 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 bond and nonbonding pairs
under which of the following temperature conditions is the reaction thermodynamically favored?
it is not favored with any temperature
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
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
which of the following is the rate law for the overall reaction that is consistent with teh proposed mechanism
rate = K[NO2]2
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
based on the bond energies listed in the table above, which of the following is closest to the bond energy of the C-N bond
300kj/mol
Based on the ionization energies of element X given in the table above, which of the following is most likely the empirical formula of an oxide element X
X2O3
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 examining the crystals of the substance under a microscope determining the density of the substance testing the electrical conductivity of the crystals testing the electrical conductivity of an aqueous solution of the substance
testing the electrical conductivity of an aqueous solution of the substance
The table above provides some information about 2 types of steel, both of whihc are alloys of iron and carbon. Which of the folloinw 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
If the absorbance of the mixture is .2 at 453 nm how many moles of Fe were present in the 100 ml sample 4x10^-4 3x10^-4 4x10^-6 3x10^-6
4x10^-6
which of the following particle views best represents the mixture when the titration is halfway to the equivalence point?
5 H2O2 ions and 2 Mn ions
Which of the following is true for the decomposition of H2O2
G<0 and Keq>1
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?
H: Positive S: Positive
which of the following statements about H for the reaction is correct
H>0 because energy is required to break the N-N bond
two trials are run, using excess water. in the first trial, 7.8 g of Na1O2 is mixed with 3.2 g of S. In the second trial, 7.8 G og Na2O2 is mixed with 6.4 G of S. The Na2O2 and S react as completely as possible. both trials yield the same amount of SO2. Which of the following identifies that limiting reactant and the heat released for the two trials at 298K
Limiting Reactant: Na2O2 q = 30 kJ
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
Which of the folloing mechanisms for the catalyzed reaction is consistent witht eh equation and diagram above?
O3 + NO --> NO2 + O2
Benzene C6H6 has the structure shown 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-induced dipole and London dispersion interactions between water and benzene
for the system represted above, O2 and O3 initially are .15mol/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 O3 will decrease because Q>Kc
two samples of Mg of equal mass were placed in equal amounts of HCl contained in 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 in Figure 1
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 Cu(NO3)2 from the sample of the mixture was not diluted properly the spectrophotometer was calibrated wiht tap water instead of distilled water the student labelled the cuvettes incorrectly, reversing the labels of the solutions of known concentrations the spectrophotometer was originally set to an inappropriate wavelength , causing the absorbance to vary unpredicatably
the student labelled the cuvettes incorrectly, reversing the labels of the solutions of known concentrations
To choose a wavelength to analyze the progress of the reaction, a student records the absorbance of both C25H30N3 and C25H30N3OH in the range of 200-800nm the two spectra are presented in the graph to the right
590 nm, because only the violet form of the molecule will absorb significantly at this wavelength
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
the process of dissolution of NaCL isH2O is represented in the diagram above. Which of the following summarizes the signs of H and S for each of teh dissolution process
H+ S+, H+ S+, H- S-
a 1 mol sample of CO and a 1 mol sample of H2 are pumped into a rgid, previously evacuated 2 L reaction vessel at 438K which of the following is true at equilibirum
H2<CO
a .1 mol sample of each of the four species in the reaction represented above is injected into a rigid, previously evacuated 1 L container. Which of the following species will have the high concentration when the system reaches equilibrium
H2S
Each student in a class is placed a 2 g sample of a mixture of CU and AL in fume hood. The students slowly poured 15 ml of 15.8M HNO3 into their beakers It is a bronsted lowery acid base reaction, because the solution is neutral at the end It is a bronsted lowery acid base reaction, because HNO3 is a strong acid It is a redox reaction, because CU is oxidized and H is reduced It is a redox reaction, because CU is oxidized and the nitrogen atom in NO3 is reduced
It is a redox reaction, because CU is oxidized and the nitrogen atom in NO3 is reduced
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 H only
What can be inferred about s for the reaction at 600K
It must be positive, since G is negative, and H is positive
Which of the following explains the effect on the equilibrium constant Kc when the temperature of the reaction system is increased to 650K
Kc will decrease because the reaction is exothermic
Acid dissociation constants of two acids are listed in the table above. A 20 mL sample of .1m solution of each acid is titrated to the equivalence point with 20mL of .1 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.
NH3 reacts with BF3 to form a single species. which of the folloing structural diagrams is the most likely representation of the product of the reaction.
[3H on N connected with 3F on B]
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, 0-2 molecule] [4-3 molecule, 1-2 molecule] [2-3 molecule, 4-2 molecule] [7-3 molecule, 0-2 molecule]
[4-3 molecule, 1-2 molecule]
A mixture of Co and H2 is pumped into a previously evacuated 2L reaction vessel. the toal 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
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
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
a student performed an analysis to determine the amount of AgNO3 in a solution. Excess NACL was added to the solution, and teh AG precipitates as AgCl. The precipitate was collected by gravity filtraction and dried in an oven
the precipitate was not rinsed with deionized water before drying
When H2 and O2 are mixed together in a rigid reaction vessel at 20 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 gases are originally at 25 C
the reaction has a large activation energy at 25 C