First Semester Final- AP Chem

At 25°C, aqueous solutions with a pH of 8 have a hydroxide ion concentration, [OH-], of...

1x10^-6 M

...Ca3(PO4)2(s) + ...H3PO4(l) --> ...Ca(H2PO4)2(s) When the equation above is balanced and all coefficients are reduced to the lowest whole number terms, what is the coefficient for H3PO4(l)?

4

10HI + 2KMnO4 + 3H2SO4 --> 5I2 + 2MnSO4 + K2SO4 + 8H2O According to the balanced equation above, how many moles of HI would be necessary to produce 2.5 mol of I2, starting with 4.0 mol of KMnO4 and 3.0 mol of H2SO4?

5.0

What is the H+(aq) concentration in 0.05M HCN(aq)? The Ka for HCN is 5.0 x 10^-10.

5.0x10^-6 M

At 25°C and 1 atm, is a strong electrolyte in aqueous solution

HBr

The solution with the lowest pH

HCl and NaCl

When hafnium metal is heated in an atmosphere of chlorine gas, the product of the reaction is found to contain 62.2% Hf by mass and 37.4% Cl by mass. What is the empirical formula for this compound?

HfCl3

H2(g) + I2(g) <--> 2HI(g) delta H>0 Which of the following changes to the equilibrium system represented above will increase the quantity of HI(g) in the equilibrium mixture? I. adding H2(g) II. increasing the temperature III. decreasing the pressure

I and II only

Appropriate uses of a visible-light spectrophotometer include which of the following? I. determining the concentration of a solution of Cu(NO3)2 II. measuring the conductivity of a solution of KMNO4 III. determining which ions are present in a solution that may contain Na+, Mg2+, Al3+

I only

Factors that affect the rate of a chemical reaction include which of the following? I. Frequency of collisions of reactant particles II. Kinetic energy of collisions of reactant particles III. Orientation of reactant particles during collisions

I, II, and III

Which of the following is the conjugate acid of NH2?

NH3

A compound contains 30% sulfur and 70% fluorine by mass. The empirical formula of the compound is...

SF4

Which of the following ions has the same number of electrons as Br-?

Sr^2+

The substance is at its normal freezing point at time

T2

HCO3(aq) + OH(aq) <--> H2O(l) + CO3(aq) delta H= -41.4 When the reaction represented by the equation above is at equilibrium at 1 atm and 25°C, the ratio [CO3]/[HCO3] can be increased by doing which of the following?

decreasing the temperature

All of the halogens in their elemental form at 25°C and 1 atm are...

diatomic molecules

reacts with water to form a strong base

lithium

A sample of 61.8 g of H3BO3, a weak acid, is dissolved in 1,000 g of water to make a 1.0-molar solution. Which of the following would be the best procedure to determine the molarity of the solution? (Assume no additional information is available.)

measurement of the total volume of the solution

Which of the following must be true for a reaction for which the activation energy is the same for both the forward and the reverse reactions?

Delta H for the reaction is zero

True for the combustion of liquid pentane, C5H12(l) to form H2O(g) and CO2(g) at 1 atm.

Delta H<0, delta S>0

A solution of a weak monoprotic acid is titrated with a solution of a strong base, KOH. Consider the points labeled (A) through (E) on the titration curve the results, as shown below. The point at which the pH is closest to that of the strong base being added.

E

Which of the following techniques is the most appropriate for the recovery of solid KNO3 from an aqueous solution of KNO3?

Evaporation to dryness

PCl3(g) + Cl2(g) <--> PCl5(g) + energy Some PCl3 and Cl2 are mixed in a container at 200°C and the system reaches equilibrium according to the equation above. Which of the following causes an increase in the number of moles of PCl5 present at equilibrium? I. Decreasing the volume of the container II. Raising the temperature III. Adding a mole of He gas at constant volume

I only

Appropriate laboratory procedures include which of the following? I. rinsing a buret with distilled water just before filling it with the titrant for the first titration II. lubricating glass tubing before inserting it into a stopper III. For accurate results, waiting until warm or hot objects have reached room temperature before weighing them

II and III only

3Cu(s) + 8H(aq) + 2NO3(aq) --> 3Cu(aq) + 2NO(g) +4H2O(l) True statements about the reaction represented above include which of the following? I. Cu(s) acts as an oxidizing agent II. the oxidation state of nitrogen changes from +5 to +2 III. hydrogen ions are oxidized to form H2O(l)

II only

Mixtures that would be considered buffers include which of the following? I. 0.10 M HCl + 0.10 M NaCl II. 0.10 M HF + 0.10 M NaF III. 0.10 M HBr + 0.10 M NaBr

II only

The graph below shows the titration curve that results when 100. mL of 0.0250 M acetic acid is titrated with 0.100M NaOH. Which of the following indicators is the best choice for this titration?

Indicator: Phenolphthalein pH Range of Color Change: 8.2-10.0

the graph above shows the results of a study of the reaction of X with a large excess of Y to yield Z. The concentrations of X and Y were measured over a period of time. According to the results, which of the following can be concluded about the rate law for the reaction under the conditions studied?

It is first order in [X].

A compound contains 1.10 mol of K, 0.55 mol of Te, and 1.65 mol of O. What is the simplest formula of this compound?

K2TeO3

On the basis of the solubility curves shown above, the greatest percentage of which compound can be recovered by cooling a saturated solution of that compound from 90° to 30°?

KNO3

Commercial vinegar was titrated with NaOH solution to determine the content of acetic acid, HC2H3O2. For 20.0 milliliters of the vinegar 26.7 milliliters of 0.600-molar NaOH solution was required. What was the concentration of acetic acid in the vinegar if no other acid was present?

.800 M

2H2O(l) + 4MnO4(aq) + 3ClO2(aq) --> 4MnO2(s) + 3ClO4(aq) + 4OH(aq) According to the balanced equation above, how many moles of ClO2(aq) are needed to react completely with 20. mL of 0.20 M KMnO4 solution?

0.0030 mol

A 360. mg sample of aspirin, C9H8O4, (molar mass 180. g), is dissolved in enough water to produce 200. mL of solution. What is the molarity of aspirin in a 50. mL sample of this solution?

0.0100 M

What is the final concentration of barium ions, [Ba2+], in solution when 100. mL of 0.10 M BaCl2(aq) is mixed with 100. mL of 0.050 M H2SO4(aq)?

0.025 M

Which of the following solutions has a pH greater than 7.0?

0.10 M NaF

If 200. mL of 0.60 M MgCl2(aq) is added to 400. mL of distilled water, what is the concentration of Mg2+(aq) in the resulting solution? (assume volumes are additive)

0.20 M

If 0.40 mol of H2 and 0.15 mol of O2 were to react completely as possible to produce H20, what mass of reactant would remain?

0.20 g of H2

A 40.0 mL sample of 0.25 M KOH is added to 60.0 mL of 0.15 M Ba(OH)2. What is the molar concentration of OH-(aq) in the resulting solution? (Assume that the volumes are additive.)

0.28 M

A 1.0 L sample of an aqueous solution contains 0.10 mol of NaCl and 0.10 mol of CaCl2. What is the minimum number of moles of AgNO3 that must be added to the solution in order to participate all of the Cl- as AgCl(s)? (Assume that AgCl is insoluble.)

0.30 mol

____C10H12O4S(s) + ____O2(g) --> ____CO2(g) + ____SO2(g) + ____H2O(g) When the equation above is balanced and all coefficients are reduced to their lowest whole-number terms, the coefficient for O2(g) is

12

Which of the following pieces of laboratory glassware should be used to most accurately measure out a 25.00 mL sample of a solution

25 mL pipet

The atomic mass of copper is 63.55. Given that there are only two naturally occurring isotopes of copper, 63Cu and 65Cu, the natural abundance of the 65Cu isotope must be approximately...

25%

In a saturated solution of Zn(OH)2 at 25°C, the value of [OH-] is 2.0 x 10^-6 M. What is the value of the solubility product constant, Ksp, for Zn(OH)2 at 25°C?

4.0x10^-18

2 N2H4(g) + N2O4(g) --> 3 N2(g) + 4H2O(g) When 8.0 g of N2H4 (32g/mol) and 92 g of N2O4 (92g/mol) are mixed together and react according to the equation above, what is the maximum mass of H2O that can be produced?

9.0 g

The diagram above represents H2(g) and N2(g) in a closed container. Which of the following diagrams would represent the results if the reaction shown below were to proceed as far as possible? N2(g) + 3H2(g) --> 2NH3(g)

A

Barium sulfate is LEAST soluble in a 0.01 molar solution of which of the following?

Al2(SO4)3

The cooling curve for a pure substance as it changes from a liquid to a solid is shown above. The solid and liquid coexist at

All points on the curve between Q and S

A solution of a weak monoprotic acid is titrated with a solution of a strong base, KOH. Consider the points labeled (A) through (E) on the titration curve the results, as shown below. The point at which the concentration of the weak acid and its conjugate base are approximately equal.

B

In which of the following compounds is the mass ratio of chromium to oxygen closest to 1.62 to 1.00?

CrO2

2SO3(g) <--> 2SO2(g) + O2(g) After the equilibrium represented above is established, some pure O2(g) is injected into the reaction vessel at constant temperature. After equilibrium is reestablished, which of the following has a lower value compared to its value at the original equilibrium?

The amount of SO2 (g) in the reaction vessel

When 100 mL of 1.0 M Na3PO4 is mixed with 100 mL of 1.0 M AgNO3, a yellow precipitate forms when [Ag+] becomes negligibly small. Which of the following is a correct listing of the ions remaining in solution in order of increasing concentration?

[PO43-]<[NO3-]<[Na+]

Ionization constants CH3COOH = 1.8 x 10^-5 NH3 = 1.8 x 10^-5 H2CO3; K1 = 4 x 10^-7 H2CO3; K2 = 4 x 10^-11 A solution prepared to be initially 1 M in NaCl and 1 M in HCl.

a solution with a pH less than 7 that is not a buffer solution

salts containing which of the following ions are generally insoluble in cold water? a. nitrate b. acetate c. phosphate d. potassium e. ammonium

phosphate

2NO(g) + O2(g) --> 2NO2(g) A possible mechanism for the overall reaction represented above is the following. 1) NO(g) + NO(g) --> N2O2(g) slow 2) N2O2(g) + O2(g) --> 2NO2(g) fast Which of the following rate expressions agrees best with this possible mechanism?

rate = k[NO]^2

2A(g) + B(g) <--> 2C(g) When the concentration of substance B in the reaction above is doubled, all other factors being held constant, it is found that the rate of the reaction remains unchanged. The most probable explanation for this observation is that...

substance B is not involved in the rate-determining step of the mechanism, but is involved in subsequent steps

The cooling curve above shows how the temperature of a sample varies with time as the sample goes through phase changes. The sample starts as a gas, and heat is removed at a constant rate. At which time does the sample contain the most liquid?

t4

As the number of oxygen atoms increases in any series of oxygen acids, such as HXO, HXO2, HXO3, ..., which of the following is generally true?

the acid strength increases

2NH3 <--> NH4 +NH2 In liquid ammonia, the reaction represented above occurs. In the reaction NH4 acts as...

the conjugate acid of NH3

6I + 2MnO4 + 4H2O(l) --> 3I2(s) + 2MnO2(s) + OH- Which of the following statements regarding the reaction represented by the equation above is correct?

the oxidation number of iodine changes from -1 to 0

A student pipetted five 25.00 mL samples of hydrochloric acid and transferred each sample to an Erlenmeyer flask, diluted it with distilled water, and added a few drops of phenolphthalein to each. Each sample was then titrated with a sodium hydroxide solution to the appearance of the first permanent faint pink color. The following results were obtained... Which of the following is the most probable explanation for the variation in the student's results?

the pipette was not rinsed with the HCl solution

H3AsO4 + 3I + 2H3O --> H3AsO3 + I3 +H2O The oxidation of iodide ions by arsenic acid in acidic aqueous solution occurs according to the stoichiometry shown above. The experimental rate law of the reaction is: rate = k[H3AsO4][I-][H3O+] According to the rate law for the reaction, an increase in the concentration of hydronium ion has what effect on this reaction?

the rate of reaction increases

What is the molar solubility in water of Ag2CrO4? (The Ksp for Ag2CrO4 is 8 x 10^-12)

third root of 4 x 10^-12 M

A sample of 10.0 mol butyric acid, HC4H7O2, a weak acid is dissolved in 1000. g of water to make a 10.0 molar solution. Which of the following would be the best method to determine the molarity of the solution? (in each case, assume that no additional information is available.)

Measurement of the total volume of the solution

Forms a compound having the formula KXO4

Mn

A 0.10 M aqueous solution of sodium sulfate, Na2SO4, is a better conductor of electricity than a 0.10 M aqueous solution of sodium chloride, NaCl. Which of the following best explains this observation?

More moles of ions are present in a given volume of 0.10 M Na2SO4 than in the same volume of 0.10 M NaCl.

The most nearly neutral solution

NH3 and HC2H3O2 (acetic acid)

A buffer at pH > 8

NH3 and NH4Cl

All of the following species can function as Bronsted-Lowry bases in solution EXCEPT

NH4+

Each of the following can act as both a Bronsted acid and a Bronsted base EXCEPT

NH4+

A precipitation reaction

Pb2+(aq) + CrO42-(aq) -> PbCrO4(s)

What part of the curve corresponds to the optimum buffer action for the acetic acid/acetate ion pair?

Point V

The initial rate data in the table above were obtained for the reaction represented below. What is the experimental rate law for the reaction? 2NO(g) + O2(g) --> NO2(g)

Rate=k[NO][O2]^2

A reaction was observed for 20 days and the percentage of the reactant remaining after each day was recorded in the table above. Which of the following best describes the order and the half-life of the reaction?

Reaction Order: First, Half-life (days): 3

Which of the following is a correct statement about reaction order?

Reaction order can be determined only by experiment.

Forms monatomic ions with 2- charge in solutions

S

A combustion reaction

S8(s) + 8O2(g) -> 8SO2

In which of the following species does sulfur have the same oxidation number as it does in H2SO4?

SO2Cl2

The oxidation state that is common to aqueous ions of Fe, Mn, and Zn is...

+2

C2H4(g) + 3O2(g) --> 2CO2(g) + 2H2O(g) For the reaction of ethylene represented above, delta H = -1,323 kJ. What is the value of delta H if the combustion produced liquid water H20(l)? (delta H for the phase change H2O(g) --> H2O(l) is -44 kJ/mol)

-1,411 kJ

3C2H2(g) --> C6H6(g) What is the standard enthalpy change, delta H°, for the reaction represented above? Delta H°f of C2H2(g) is 230 kJ/mol; delta H°f of C6H6(g) is 83 kJ/mol.

-607 kJ

The diagram above represents a mixture of NO2(g) and N2O4(g) in a 1.0 L container at a given temperature. The two gases are in equilibrium according the equation 2NO2(g) <-->N2O4(g). Which of the following must be true about the value of the equilibrium constant for the reaction at this temperature?

0<K<1

The volume of distilled water that should be added to 10.0 mL of 6.00 M HCl(aq) in order to prepare a 0.500 M HCl(aq) solution is approximately...

110. mL

How many carbon atoms are contained in 2.8g of C2H4?

1.2x10^23

...Mg(s) + ...NO3(aq) + ...H(aq) --> ...Mg(aq) + ...NH4(aq) + ...H2O(l) When the skeleton equation above is balanced and all coefficients reduced to their lowest whole-number terms. What is the coefficient for H+?

10

2 MnO4(aq) + 10Br(aq) + 16H (aq) --> 2Mn(aq) + 5Br2(aq) +8H20(l) How many electrons are transferred in the reaction represented by the balanced equation above?

10

How many mL of 10.0 M HCl are needed to prepare 500. mL of 2.00 M HCl?

100. mL

The pH of a solution prepared by the addition of 10. mL of 0.002 M KOH(aq) to 10. mL of distilled water is closest to...

11

What mass of Au is produced when 0.0500 mol of Au2S3 is reduced completely with excess H2?

19.7g

An oxidation-reduction reaction that is also a synthesis reaction.

2Mg (s) + O2 -> 2MgO

The table above shows the results from a rate study of the reaction X + Y á Z. Starting with known concentrations of X and Y in experiment 1, the rate of formation of Z was measured. If the reaction was first order with respect to X and second order with respect to Y, the initial rate of formation of Z in experiment 2 would be...

2R

____Li3N(s) + ____H20(l) --> ____Li+(aq) + ____ OH-(aq) + ____NH3(g) When the equation above is balanced and all coefficients reduced to the lowest whole number terms, the coefficient for OH-(aq) is...

3

2 X(g) + Y(g) <--> 3 Z(g) The reaction mixture represented above is at equilibrium at 298K, and the molar concentrations are [X] = 2.0 M, [Y] = 0.5M, and [Z] = 4.0 M. What is the value of the equilibrium constant for the reaction at 298K?

32

A reaction in which the same reactant undergoes both oxidation and reduction...

3Br2(aq) + 6OH-(aq) -> 5Br-(aq) + BrO3-(aq) + 3H2O(l)

...H+(aq) + ...NO2(aq) + ...Cr2O7(aq) --> ...Cr(aq) + ...NO3(aq) + ...H2O(l) When the equation above is balanced and all coefficients are reduced to the lowest whole numbers, the coefficients for H2O(l) is...

4

The density of a pure liquid at 25°C was calculated by determining the mass and volume of a sample of the liquid. A student measures the mass of a clean, dry 25.00 mL volumetric flask, filled the flask to its calibration mark with the liquid, and then measured the mass of the flask and liquid. The recorded measurements are shown in the table above. On the basis of this information, to how many significant figures should the density of the liquid by reported?

4

Gaseous cyclobutene undergoes a first order reaction to form gaseous butadiene. At a particular temperature, the partial pressure of cyclobuten in the reaction vessel drops to 1/8th its original value in 124 seconds. What is the half-life for this reaction at this temperature?

41.3 s

Propane gas, C3H8, burns in excess oxygen gas. When the equation for this reaction is correctly balanced and all coefficients are reduced to their lowest whole-number term, the coefficient for O2 is...

5

H2(g) + Br2(g) <--> 2HBr(g) At a certain temperature, the value of the equilibrium constant, K, for the reaction represented above is 2.0 x 10^5. What is the value of K for the reverse reaction at the same temperature?

5.0x10^-6

Which of the following shows the correct number of protons, neutrons, and electrons in a neutral cesium-134 atom?

55 protons, 79 neutrons, 55 electrons

Approximately what mass of CuSO4 x 5H2O (250g/mol) is required to prepare 250 mL of 0.10 M copper(II) sulfate solution?

6.2g

Cr2O7(aq) + ...H2S(g) + ...H(aq) --> ...Cr(aq) + ...S(s) + ...H2O(l) When the equation above is correctly balanced and all coefficients are reduced to the lowest whole-number terms, the coefficient for H(aq) is...

8

Rate = k[M][N]^2 The rate of a certain chemical reaction between substances M and N obeys the rate law above. The reaction is first studied with [M] and [N] each 1 x 10^-3 molar. If a new experiment is conducted with [M] and [N] each 2 x 10^-3 molar, the reaction rate will increased by a factor of...

8

If 87.5% of a sample of pure 131-I decays in 24 days, what is the half life of 131-I?

8 days

When a 1.00 gram sample of limestone was dissolved in acid, 0.38 grams of CO2 was generated. If the rock contained no carbonate other than CaCO3 , what was the percent of CaCO3 by mass in the limestone?

86%

How can 100. mL of sodium hydroxide solution with a pH of 13.00 be converted to a sodium hydroxide solution with a pH of 12.00?

By diluting the solution with distilled water to a total volume of 1.00 L.

A solution of a weak monoprotic acid is titrated with a solution of a strong base, KOH. Consider the points labeled (A) through (E) on the titration curve the results, as shown below. The point at which the moles of the added strong base are equal to the moles of the weak acid initially present.

C

A hydrocarbon gas with an empirical formula CH2 has a density of 1.88 g/L at 0°C and 1 atm. A possible formula for hydrocarbon is...

C3H6

Ascorbic Acid, H2C6H6O6, is a diprotic acid with K1 = 7.9 x10^-5 and K2 = 1.6 x 10^-12. In a 0.005 M aqueous solution of absorbic acid, which of the following species is present in the lowest concentration?

C6H6O62- (aq)

HC2H3O2(aq) + CN(aq) <--> HCN(aq) + C2H3O2(aq) The reaction represented above has an equilibrium constant equal to 3.7 x 10^4. Which of the following can be concluded from this information?

CN- (aq) is a stronger base than C2H3O2-

A precipitation reaction

Ca2+(aq) + SO42-(aq) -> CaSO4 (s)

After completing an experiment to determine gravimetrically the percentage of water in a hydrate, a student reported a value of 38%. The correct value for the percentage of water in the hydrate is 51%. Which of the following is the most likely explanation for the difference?

The dehydrated sample absorbed moisture after heating

Which of the following best describes what happens to the substance between t4 and t5?

The molecules are leaving the liquid phase.

H2Se(g) + 4O2F2(g) --> SeF6(g) + 2HF(g) + 4O2(g) Which of the following is true regarding the reaction represented above?

The oxidation number of Se changes from -2 to +6

Which of the following is a correct interpretation of the results of Rutherford's experiments in which gold atoms were bombarded with alpha particles?

The positive charge of an atom is concentrated in a small region.

Which of the following best describes the role of the spark from the spark plug in an automobile engine?

The spark supplies some of the energy of activation for the combustion reaction.

the energy required to form the transition state in a chemical reaction.

activation energy

HgO(s) + 4I + H2O <--> HgI4 + 2OH; delta H < 0 Consider the equilibrium above. Which of the following changes will increase the concentration of HgI4?

adding 6 M HNO3

Which of the following represents acceptable laboratory practice?

adding a weighed quantity of solid acid to a titration flask wet with distilled water

When dilute nitric acid was added to a solution of one of the following chemicals, a gas was evolved. This gas turned a drop of limewater, Ca(OH)2, cloudy, due to the formation of a white precipitate. The chemical was...

baking soda, NaHCO3

Are the most likely to form anions

halogens

2 NO(g) + O2(g) <--> 2NO2(g) delta H < 0 Which of the following changes alone would cause a decrease in the value of Keq for the reaction represented above?

increasing the temperature