2017 and 2018 AP Chem Final review

... Which of the following provides the best estimate of the pH of .5M HCHO2 and identifies the species at the highest concentration in the solution?

(ICE table) 2, HCHO2

Based on the values of G for the three reactions above, what is the value of G for the reaction below?

-1320

2018 (21) In an experiment a student mixes a 50.0 mL sample of 0.100 M AgNO3 (aq) with a 50.0 mL sample of 0.100 M NaCl (aq) at 20 degrees C. Which of the following is the enthalpy change... final temperature is 21 degrees C?

-84 kJ/molrxn

(43) What is the value of the enthalpy change per mole of HCl (g) produced

-93 kJ

2018 (16) The temperature of the CH3OH (l) is increased from 300k to 400k to vaporize all the liquid...

0.15 atm

2018 (15) The value of Kp for the evaporation of CH3OH (l) at 300 K is closest to

0.2

2018 (22) If 3.8 g of Cu3(PO4)2 (s) was recovered from step 1, what was the approximate Cu^2+ in the OG solution? (molar mass 381 g/mol)

0.30 M

(38) Based on the thermodynamic data, which of the following is true at 298 K

0<k<1

(31) The pH of a solution made by combining 150 mL of .10 M KOH with 50.0 mL of .20 M HBr is closest to...

12

A 0.03 mol sample of NO2 is placed in a rigid 1 L reaction vessel and allowed to reach equilibrium at a certain temp. What is the value of Kc... if 0.005 mol N2O4 is present?

12.5

(22) If P(N2O4) is 1.33 atm when the system is at equilibrium at 70 C which is P(NO2)

2 atm

2018 (11) On the basis of the information above, what is the approximate percent ionization of HNO2 in a 1.0 M HNO2 (aq) solution?

2.0%

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 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

When 70 g of Li3Ni (s) reacts with excess H2, 8 g of LiH is produced. The percent yield is closest to...

25

(58) A 0.35 g sample of Li (s) is placed in an Erlenmeyer flask containing 100 mL of water at 25 C. A balloon is places over the mouth of the flask to collect the hydrogen gas that is generated. After all of the Li (s) has reacted with H2O (l), the solution in the flask is added to a clean, dry buret and used to titrate an aqueous solution of a monoprotic acid. The pH curve for this titration is shown in the diagram below. Which of the following is the balanced net ionic equation for the reaction between Li (s) and water?

2Li (s) + 2 H2O --> 2 Li + (aq) + 2 OH- (aq) +H2 (g)

(37) 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

(12) The students determined that the reaction produced .01 mol of CuNO3.

32%

(26)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

(5) 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

(57) A 0.35 g sample of Li (s) is placed in an Erlenmeyer flask containing 100 mL of water at 25 C. A balloon is places over the mouth of the flask to collect the hydrogen gas that is generated. After all of the Li (s) has reacted with H2O (l), the solution in the flask is added to a clean, dry buret and used to titrate an aqueous solution of a monoprotic acid. The pH curve for this titration is shown in the diagram below. On the basis of the pH curve, the pKa value of the acid is closest to.....

5

(35) 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

2018 (14) Which of the following best describes the change that takes place immediately after the CH3OH (l) is introduced introduced into the previously evacuated vessel?

A physical change takes place because intermolecular attractions are overcome

ClO 2- (aq) +HCOOH (aq) <-> HClO2 (aq) + HCOO- (aq) Keq < 1 What are the relative strengths of the acids and bases in the reaction represented by the equation above?

Acid Strength: HClO2 > HCOOH Base Strength: ClO2 - < HCOO-

Which of the following changes would result in more NH3 in the mixture after equilibrium is reestablished?

Adding some N2

2018 (28) Which of the following changes will decrease Ca^2+ in a saturated solution of CaF2 and why?

Adding some NaF (s) because the reaction will proceed towards towards the reactants

Ag + (aq) +NH3 <-> AG(NO3)+ (aq) Keq1 = 2E3 Ag(NH3)+ (aq) +NH3 <-> Ag(NH3)2 + Keq2 = 8E3 Equal volumes of 0.1M Ag(NO3) (aq) and 2.0M NH3 (aq) are mixed and the reactions above occur. Which Ag species will have the highest concentration in the equilibrium system shown below, and why? Ag+ (aq) + 2NH3 (aq) <-> Ag(NH3)2 + (aq) . Keq3=?

Ag(NH3)2 + (aq), because Keq3 =1.6E7

(6) The first ionization energy of an element is the energy required to remove an electron form a gaseous atom of an element

Al + Mg --> Al + Mg

2018 (5) A 1.0 L sample of a pure gas is found to have a lower pressure than that predicted by the ideal gas law. The best explanation for the observation is that the molecules of the gas

Are attracted to each other and do not exert as much force on the container walls as they would if they had no mutual attractions

Which of the following best help explain why an increase in temp increases the rate of chem. reaction?

At high temp, high energy collisions happen more frequently

2018 (18) Which of the following Lewis electron-dot diagrams... most polar?

Br-F

An acetate buffer solution is prepared by combining 50mL of 0.2M acetic acid, HC2H3O2(aq), and 50mL of 0.2M sodium acetates NaC2H3O2(aq). A 5.0mL sample of 0.1M NaOH (aq) is added to the buffer solution. Which of the following is the correct pairing of the acetate species present in greater concentration and of the pH of the solution after the NaOH (aq) is added (the pKa of acetic acid is 4.7)

C2H3O2-, pH > 4.7

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 IMAF include dipole-dipole forces?

CH2F2

2018 (30) Which of the following equations represents the reaction that accounts for the fact that the pH does not change significantly when the HNO3 (aq) is added?

CH3NH2 + H--> CH3NH3

2018 (6) Equal volumes of solutions in two different vessels are represented above. If the solution represented in vessel 1 is KCl (aq) then the solution represented in vessel 2 could be an aqueous solution of

CaCl2 with twice the molarity of the solution in vessel 1

2H2O2 (l) -> 2H2O(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

What happens to the temp of the contents of the vessel as the reaction occurs?

Decrease b/c endothermic

2018 (1) Which of the following particle diagrams best represents the products when four molecules of H2O2 (l) decompose into water and oxygen gas at room temperature?

Diagram with 4H2O and 2O2

(31)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

2018 (8) The standard reduction potentials for the half-reactions related to the galvanic cell represented above are listed in the table below. Which of the following gives the value of Ecell for the cell

Ecell= +.02 V

(19) 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

2018 (27) Maxwell-Boltzmann.... greater molar mass?

Gas A

Which of the following happens to H atoms in the forward reaction?

H is both oxidized and reduced

(34) 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 student prepares a solution by combing 100mL of 0.3M HNO2(aq) and 100mL of 0.3M KNO2(aq). Which of the following equations represents the reaction that best helps to explain why adding a few drops of 1.0M HCL(aq) does not significantly change the Ph of the solution?

H+(aq) +NO2-(aq) -> HNO2 (aq)

(51) 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

H-Bond

which of the following has the bonds arranged in order of decreasing polarity

H-F>N-F>F-F

(25) Which of the following statements about H for the reaction is correct

H>0 because energy is required to break the N-N bond

2018 (7) A 20. mL sample of 0.5 M HC2H3O2 (aq) is titrated with 0.5 M NaOH. Which of the following best represents the species that react and the species produced in the reaction?

HC2H3O2(aq) + OH- (aq) ---> H2O (l) + C2H3O2- (aq)

Ne, HF, C2H6, CH4 Which of the substances listed above has the highest boiling point, and why?

HF, because its molecule form hydrogen bonds

2018 (25) Which of the following most likely describes the solid represented in the diagram to the left?

It is a brittle, water-soluble electrolyte that is a poor thermal and electrical conductor as a solid

(10) 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 redox reaction, because CU is oxidized and the nitrogen atom in NO3 is reduced

(45) Based on the information above, which of the following expressions represents the equilibrium constant, K, for the reaction represented by the equation below La 3+ + CO3 2- <-> La CO3+

K=(K1)(Kw)/(Ka)

Which of the following explains the effect on Kc when the temp... is increased to 650 K

Kc will decrease b/c exothermic

2018 (26) Which of the following best helps to explain why CCl4 is a liquid whereas CI4 is solid when both are at 25 C?

LDF are stronger in CI4 than CCL4 because CI4 has a more polarizable electron cloud than CCl4

...What will be the total pressure of the system if volume of the reaction vessel is reduced to 1 atm at constant T?

Less than 1.2 atm

The forward reaction is thermodynamically favored at which of the following temperatures?

Low temperatures only

(8) 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

... According to the info above, which of the following will occur as the system approaches equilibrium?

More HI will be produced because Q<Kc

The ideal gas law best describes the properties of which of the following gases

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

... what can be concluded regarding the strength of the C-H, N-H, and O-H bonds in the molecules shown?

O-H strongest

(32) Which of the following mechanisms for the catalyzed reaction is consistent with the equation and diagram above?

O3 + NO --> NO2 + O2

The rate of the reaction represented above increases significantly in the presence of P. Which... best explains this reaction?

One of the reactants binds on the surface of P... lower activation energy

2018 (20) For which of the equilibrium systems represented below will the amount of products at the equilibrium increase if the volume... increased at a constant T?

PCl5 (g) --> PCl3 (g) + Cl2 (g)

2018 (24) ...Which of the following chemical species had the lowest concentration among the products of step 2?

PO4^3- (aq)

2018 (29) Based on the Ksp values for the compounds listed in the table... which of the compunds will have the lowest Pb?

Pb(OH)2

A student studied the kinetics of the reaction represented below by measuring the concentration of the reactant, X, over time. Which of the following will allow the student to determine the rate constant, k, for the reaction?

Plot ln[X] versus time and determine the magnitude of the slope

2018 (4) Based on the information in the table to the left, which of the compounds has the highest boiling point, and why?

Propanoic acid, because it can form intermolecular hydrogen bonds

The step-wise dissocitaion of selenous acid H2SeO3 is represented... above... Which of the following helps to explain whe Ka2 is smaller than Ka1?

Removing the first H... requires less energy than removing the second H...

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

2018 (19) Based on Coulombs law and the info... strongest interactions with nearby water molecules in an aqueous solution?

S^2- (because of smallest radius with biggest charge)

2018 (2) The masses of carbon and hydrogen in samples of four pure hydrocarbons are given to the left. The hydrocarbon in which sample has the same empirical formula as propene, C3H6?

Sample B

(56) A 0.35 g sample of Li (s) is placed in an Erlenmeyer flask containing 100 mL of water at 25 C. A balloon is places over the mouth of the flask to collect the hydrogen gas that is generated. After all of the Li (s) has reacted with H2O (l), the solution in the flask is added to a clean, dry buret and used to titrate an aqueous solution of a monoprotic acid. The pH curve for this titration is shown in the diagram below. What will be the effect on the amount of gas produced if the experiment is repeated using 0.35 g K(s) instead of 0.35 g Li (s)?

Some gases will be produced but less than the amount of gas produced with Li (s)

2018 (23) The mass of the Cu (s) produced in step 3 was slightly more than the mass predicted... Which of the following could account for the discrepancy in the yield of Cu (s) from step 3?

Some unreacted Zn (s) was mixed in with the Cu (s)

Which of the following experimental techniques will allow the most accurate determination of the concentration of NO2 at the equilibrium?

Spectrometry

2018 (10) 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

(59) Benzene, C6H6, has a 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.

The dipole-induced dipole and LDF between water and benzene

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 is true?

The heat energy lost by the Fe will be equal to the heat energy gained by the water

Which of the following is the most likely reason that the reaction occurs at a significant rate only if the temperature of the reaction mixture is greater than 200 C?

The reaction has a high activation energy

2H2 (aq) + O2 (g) --> 2H20 (g) When H2 (g) and O2 (g) are mixed together in a rigid reactio 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 of the reaction to occur when the gases are originally at 25 C?

The reaction has a large activation energy at 25 C.

(54) 2XY (g) <-> X2 (g) + Y2 (g) . Kp =230 A certain gas, XY (g), decomposes as represented by the equation above. A sample of each of the three gasses is put in a previously evacuated container. The initial partial pressures of the gases are shown in the table below XY . 0.010 X2 . 0.20 Y2 . 2.0 The temperature of the reaction mixture is held constant. in which direction will the reaction proceed?

The reaction will form more reactant

2018 (13) A balloon is filled with .25 moles He (g) at 273 K and 1.0 atm is allowed to rise through the atmosphere. Which of the following explains what happens to the volume of the balloon as it rises from ground level to an altitude where the air temperature is 220 K and the air pressure is .10 atm?

The volume will increase because the decrease in air pressure will have a greater effect than the decrease in temperature.

(55) A 0.35 g sample of Li (s) is placed in an Erlenmeyer flask containing 100 mL of water at 25 C. A balloon is places over the mouth of the flask to collect the hydrogen gas that is generated. After all of the Li (s) has reacted with H2O (l), the solution in the flask is added to a clean, dry buret and used to titrate an aqueous solution of a monoprotic acid. The pH curve for this titration is shown in the diagram below. Which of the following changes will most likely increase the rate of the reaction between Li(s) and water?

Using a 0.35 g sample of Li(s) cut into smaller pieces

Acid base graph

WA with SB

2018 (3) Three substances were studied in the laboratory, and the data in the table above were collected. Based on the data, which of the following shows the type of bonding in each substance?

X- Network Cov. Y-Metallic. Z-Ionic.

2018 (9) The ionization energies of an unknown element, X, are listed in the table to the left. Which of the following is the most likely empirical formula of a compound formed from element X and phosphorus, P?

X3P2

(39) 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

(1) The mass spectrum of an average sample of a pure element is shown in the figure above

Zr

(30) 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]

(9) 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]

A 1 mol sample of CO and a 1 mole sample of H2... what must be true at equilibrium?

[H2]<[CO]

A mixture of NO2 and N2O4 is at equilibrium... if the temp decreases then...

[N2O4] will increase and the mixture will turn LIGHTER

(7) In the reaction represented above, what is the hybridization of the C atoms before and after the reaction occurs

before sp^2 after sp^3

problem 47

black 1 goes to white 2

(20) 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

Mg(OH)2 (s) <-> Mg 2+ (aq) + 2OH- (aq) The exothermic dissolution of Mg(OH)2 (s) in water is represetnted by the equation above. The Ksp of Mg(OH)2 is 1.8E-11. Which of the following changes will increase the solubility of Mg(OH)2 in an aqueous solution

decreaseing 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 molecules

The amount of H2 present at equilibrium can be maximized by

increasing temp and decreasing pressure by increasing volume

(36) Under which of the following temperature conditions is the reaction thermodynamically favored?

it is not favored with any temperature

Which of the following shows the relationship between K1 and K2 in the reactions represented above?

k2= 1/(k1)^2

2018 (12) The equation above represents an elementary step in a chemical reaction. Which of the following is the correct expression for the rate law of the elementary step?

k[NOBr]^2

Entropy decrease?

l-s

2018 (17) Compared to the equilibrium vapor pressure of CH3OH (l) at 300k, the equilibrium vapor pressure of C2H5OH (l) at 300k is...

lower, because London dispersion forces among C2H5OH (l) molecules are greater than those among CH3OH (l)

(24) 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

What can be inferred about S for the reaction at 600k

positive because -G and +H

(28) Which of the following is the rate law for the overall reaction that is consistent with the proposed mechanism

rate = K[NO2]2

(60) Acid dissociation constants of two acids are listed int eh table above. A 20mL sample of 0.1M solution of each acid is titrated to the equivalence point with 20mL of 0.1M 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.

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

(27)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

(41) For the system repressed 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

(23) 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

Cl-(aq) +ClO-(aq) + 2H+(aq) --> Cl2(g) + H2O(l) 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

(33) 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

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

(11) 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

(13) 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

(42) Which of the following statement identifies the greates single reasont aht 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