AP Chemistry Final Semester 2

Which of the following correctly defines a Bronsted-Lowry Base?

Accepts a hydrogen Ion

(lists 3 beakers)... Each beaker contains 100mL of the indicated acidic solution, all with a pH of 3.00. Ka for HNO2 = 4.0x10^-4

All have the same hydrogen ion concentration

Which solution has the highest percent ionization?

Beaker 1 and 3 are equally high

If 50 mL of 0.1M NaOH was added to each beaker, which resulting solution would have the lowest pH?

Beaker 2 has the lowest pH

Which of the following would be classified as the conjugate base of a strong acid?

Br-1

Three ionic salts, AX, BX2, and CX3, each have a solubility of 2x10^-5 M. Which of the following correctly ranks the Ksp of the three salts from least to greatest.

CX3 < BX2 < AX

N2(g) + 3H2(g) <> 2NH3 + heat For the reaction above, which of the following statements is true regaurding an equilibrium mixture?

Cooling the mixture shifts the reaction toward products

Consider the reaction at 25C: 2N2O5(g) <> 4NO2(g) + O2(g) at 25C (lists H and S)..... which of the following is true for this reaction?

H opposes the reaction, but S favors it

What is the conjugate acid of HPO4^-2?

H2PO4^-

Consider the following information about diprotic acid, ascorbic acid. (H2As for short, molar mass 176.1) lists the steps The titration curve of disodium ascorbate, Na2As, with standard HCl is shown below: shows graph What major species is (are) present at point III?

HAs- and H2As

You wish to construct a buffer of pH= 7.0. Which of the following weak acids (with corresponding conjugate base) would you select?

HClO (hypochlorous acid) Ka 3.5 x 10^-8

Which of the following correctly ranks the acids in order of decreasing strength?

HClO4 > H2SO4 > H3PO4

Which of the following statements is correct?

HNO3 is a stronger acid than HNO2

A 0.50 M solution of an unknown acid has a pH= 4.0. Of the following, which is the identity of the acid in this solution?

HOCl (Ka=2.0x10^-8)

The hydrogen sulfate or bisulfate ion, HSO4-, can act as either an acid or a base in water. In which of the following equations does HSO4- correctly act as an acid?

HSO4- + H20 <> SO4^-2 + H30+

Given the equation S(s) + O2(g) <> SO2(g), H=-296 kJ, which of the following statement(s) is (are) true?

I, II and III are true

Hi is a strong acid whereas HF is a weak acid. Which of the following is true?

If a 1M solution of HI is prepared, [I-] is approximately 1 M

A solution of a weak base is titrated with a solution of a standard strong acid. The progress of the titration is followed with a pH meter. Which of the following observations would occur?

Initially the pH of the solution drops slowly, and then it drops more rapidly.

Which of the following is true about chemical equilibrium?

It is microscopically dynamic and macroscopically static

Which of the following is the equilibrium constant expression for the dissociation of the HOCl acid?

K= [H+][OCl-]/[HOCl]

The following questions (8-11) refer to the reaction between nitric oxide and hydrogen 2NO + H2 > N2O + H2O What are the units for the rate constant for this reaction?

L^2/mol^2*s

The experimental rate law for the decomposition of nitrous oxide (N2O) to N2 and O2 is Rate= k[N2O]^2. Two mechanisms are produced lists mechanisms Which of the following could be a correct mechanism

Mechanism II, with the second step as the rate-determining step if the first step is a fast equilibrium step

The following reaction has a K= 4.7 at 150 C. What changes will occur as a system in which [NO2]= 0.50M and [N2O4]= 1.50M approaches equilibrium. 2NO2(g) <> N2O4(g)

N2O4(g) will form NO2(g) because Q>K

Which of the following is a conjugate acid/base pair?

NH4+ & NH3

P4(g) + 5O2(g) <> P4O10(g) The above components are at equilibrium in a 1 L flask at 25 C. If 0.25 moles of gaseous chlorine is added to the flask, which of the following is true?

No effect on the reaction

The following questions (8-11) refer to the reaction between nitric oxide and hydrogen 2NO + H2 > N2O + H2O What is the rate law for this reaction?

Rate= k[NO]^2[H2]

Consider the reaction X > Y + Z. which of the following is a possible rate law?

Rate=k[X]

In a research project, a scientist adds 0.1 mole of HCN, 0.1 mole of H30+, and 0.1 mole of CN- to water to make a total volume of 1 L. Will this reaction proceed to a greater extent in the forward direction or in the reverse direction (lists reaction and Ka value)

Reverse; the K value is less than 1

A 50.0 mL sample of an acid, HA, of unknown molarity is titrated, and the pH of the resulting solution is measured with a pH meter and graphed as a function of the volume of 0.100 M NaOH added. Which of the following is the best particulate representation of the species (other than H2O) that are present in significant concentrations in the solution at point U in the titration?

Solution with 1 OH-, 2 A-, and 3 Na=

Which of the following is true about a system at equilibrium?

The [reactant(s)] is equal to the [product(s)]

For the following reaction the standard enthalpy change is +16.1 kJ/mol 2NOBr(g) <> 2NO(g) + Br2(g) Which of the following will be true if the temperature of the system is decreased, with pressure held constant?

The concentration of Br2 will decrease.

How would the net-ionic equation written for a catalyzed reaction differ from the net-ionic equation written for the same reaction without a catalyst?

The net-ionic equation would be the same because a catalyst is neither a reactant nor a product

P4(g) + 5O2(g) <> P4O10(g) Which of the following occurs for the above reaction after the removal of O2?

The rate of the reverse reaction increases, and the value of K remains the same.

What would happen if the kinetic energy of the reactants was not enough to provide the needed activation energy?

The reactants would continue to exist in their present form

For a particular chemical reaction H = 6.8 kJ and S = -29 J/K. Under what temperature conditions is the reaction spontaneous?

The reaction is not spontaneous at any possible temperatures

H2(g) + I2(g) <> 2HI(g) (at 425C, K=9.00) Hydrogen gas, iodine vapor, and hydrogen iodide gas are added to an evacuated flask until the concentrations of H2 and I2 are both 2.0M and that of HI equals 8.0M Once the system reaches equilibrium at 675C, additionally H2 is added and the temperature is held constant. Which statement best describes how this affects the value of K?

The value of K remains constant because the temperature remained constant

For the reaction, CO2(g) + 4H2(g) <> CH4(g) + 2H2O(g), K= 8.2x10^19 at 25 C. Beginning with 1M each of the carbon dioxide and hydrogen gas at 25C, which substance will have the highest concentration in the equilibrium mixture?

Water Vapor

The solubility equations and Ksp values for two different chloride salts are shown below NaCl(s) <> Na+(aq) + Cl-(aq) Ksp= 36 AgCl(s) <> Ag+(aq) + Cl-(aq) Ksp= 1.6x10^-10

With NaCl, the forward reaction is favored. The relatively large equilibrium constant tells us that the product s are favored

Given the equilibrium constants for the following elementary reactions... lists the steps... what is K for the following system? 2CU(s) + O2 <> 2CuO(s)

[(K1)/(K2)]^1/2

Which of the following is the most basic solution?

[H+]= 1.0x10^-11 M

Sodium fluoride dissolves in water and undergoes hydrolysis. What is the equilibrium law for the hydrolysis reaction?

[HF][OH-]/[F-]

Which letter shows the activation energy required for this reaction without the use of a catalyst shows graph

a

Pure SO3 is added to the reaction vessel

(A)

The temperature is increased from 25 C to 75 C

(B)

Pure O2 is added to the reaction vessel

(E)

The container is compressed to a smaller volume at constant temperature

(F)

At 25C, the following heats of reaction are known (lists reactions) At the same temperature, calculate H for the reaction: CIF + F2 > CIF3

-108.7 kJ/mol

Consider the reaction at 25C: 2N2O5(g) <> 4NO2(g) + O2(g) at 25C (lists H and S)..... Calculate G for the reaction at 25C

-25.2 kJ

Find H for the following reaction given the following bond energies: 2H2(g) + O2(g) > 2H2O(g)

-481 kJ/mol

A chemical reaction that is first order in X is observed to have a rate constant of 2.2x10^-2s^-1. if the initial concentration of X is 1.0M, what is the concentration of X after 205 s?

0.011M

CH4(g) + CO2(g) <> 2CO(g) + 2H2(g) A 1.00 L container is filled with 0.30 mol of CH4 and 0.40 mol of CO2, and allowed to come to equilibrium. At equilibrium, there are 0.20 mol of CO in the flask. What is the value fo Kc, the equilibrium constant, for the reaction?

0.027

Consider the equation A(aq) + 2B(aq) <> 3C(aq) + 2D(aq). In one experiment, 45.0 mL of 0.050M A is mixed with 25.0 mL 0.100M B. At equilibrium the concentration of C is 0.0410M. Calculate K.

0.040

COCl2(g) <> CO(g) + Cl2(g) COCl2(g) decomposes according to the equation above. When pure COCl2(g) is injected into a rigid, previously evacuated flask at 690K, the pressure in the flask is initially 1.0 atm. After the reaction equilibrium at constant temperature, the total pressure in the flask is 1.2 atm. What is the value of Kp for the reaction at 690K?

0.050

Which solution is expected to have the lowest pH?

0.1M AlCl3

For the reaction given below, 2.00 moles of A and 3.00 moles of B are placed in a 6.00 L container. At equilibrium, the concentration of A is 0.282 mol/L. What is the concentration of B at equilibrium? A(g) + 2B(g) <> C(g)

0.398 mol/L

When you exercise, the burning sensation that sometimes occurs in your muscles represents the buildup of lactic acid (HC3H5O3). In a 0.20M aqueous solution, lactic acid is 2.6% dissociated. What is the value of Ka for this acid?

1.4x10^-4

The reaction: H2(g) + I2(g) <> 2HI(g) has Kp= 45.9 at 763K. A particular equilibrium mixture at that temperature contains gaseous HI at a partial pressure of 4.00 atm and hydrogen gas at a partial pressure of 0.229 atm. What is the partial pressure of I2?

1.52 atm

Barium carbonate has a measured molar solubility of 3.96x10^-5 at 25 C. Determine the Ksp. Show all work

1.57x10^-9

Find the solubility (in mol/L) of lead(II) chloride at 25C. Ksp= 1.57x10^-5. Show all work

1.58x10^-2

2N2O5(g) <> 4NO2(g) + O2(g) Dinitrogen pentoxide is added to an evacuated rigid container at 25 C. Given that the initial pressure is 1.00 atm and at equilibrium the pressure of N2O5 is 0.500 atm, determine the overall pressure in the reaction vessel at equilibrium.

1.75

A sample of solid NH4NO3 was placed in an evacuated container and then heated so that it decomposed explosively according to the equation below. At equilibrium the total pressure in the container was found to be 2.35 atm at a temperature of 500 C. Calculate Kp. NH4NO3(s) <> N2O(g) + 2H2O(g)

1.92

Calculate the pH of a 0.55 M NH3 solution (Kb= 1.8x10^-5)

11.50

How much heat is required to raise the temperature of a 4.48 g sample of iron (specific heat = 0.450 J/gC) from 25.0 C to 79.8 C

110 J

Consider the reaction at 25C: 2N2O5(g) <> 4NO2(g) + O2(g) at 25C (lists H and S)..... Calculate H for the reaction

110.030 kJ

The average rate of disappearance of ozone in the reaction 2O3(g) > 3O2(g) is found to be 8.51x10^-3 atm/s over a certain interval of time. What is the rate of appearance of O2 during this interval?

12.8x10^-3 atm/s

Calculate the pOH of a 0.60 M solution of HCl

13.78

H2(g) + I2(g) <> 2HI(g) (at 425C, K=9.00) Hydrogen gas, iodine vapor, and hydrogen iodide gas are added to an evacuated flask until the concentrations of H2 and I2 are both 2.0M and that of HI equals 8.0M Determine the value of Q

16

Determine G for the weak acid, HF, at 25.0 C. (Ka = 7.18x10^-4)

17.9 kJ

Calculate the [H+] in a solution that has a pH of 8.67

2.1x10^-9 M

Barium iodate (Ba(IO2)2) has a Ksp of 4.0x10^-9. What is the iodate ion concentration in a saturated solution of barium iodate?

2.ox10^-3

for which of the following processes would S be expected to be most positive as written?

2NH4NO3(s) > 2N2(g) + O2(g) + 4H2O(g)

A 0.10 molar solution of acetic acid (CH3COOH) has a pH of about...

3

Consider the following processes: (lists processes) For how many of these is S positive?

3

The following questions (8-11) refer to the reaction between nitric oxide and hydrogen 2NO + H2 > N2O + H2O What is the order of this reaction?

3

What is the pH of a solution made by adding 200 mL of distilled water to 100 mL of 0.0030M HCl? (Assume volumes are additive)

3.0

At a given temperature, K= 0.033 for the equililbrium: PCl5(g) <> PCl3(g) + Cl2(g) What is K for: Cl2(g) +PCl3(g) <> PCl5(g)?

30.

If the equilibrium constant for A + B <> C is 0.180, then what is the equilibrium constant for 2C <> 2A + 2B?

30.9

The following questions (8-11) refer to the reaction between nitric oxide and hydrogen 2NO + H2 > N2O + H2O What is the magnitude of the rate constant for this reaction?

300

H2(g) + I2(g) <> 2HI(g) (at 425C, K=9.00) Hydrogen gas, iodine vapor, and hydrogen iodide gas are added to an evacuated flask until the concentrations of H2 and I2 are both 2.0M and that of HI equals 8.0M The reaction vessle is heated to 675 C, where the equilibrium concentration of the HI is determined to be 6.0M. What is the K value at 675C?

4.0

A weak acid, HZ, has a Ka of 1.0x10^-7. What is the pH of a 0.10M solution of HZ?

4.00

The salt MX2, has a solubility of 1.0x10^-4. Determine the Ksp for MX2

4.0x10^-12

If an acid, HA, is 19.7% dissociated in a 1.0M solution, what is the Ka for the acid?

4.8x10^-2

A first order reaction is 45% complete at the end of 35 minutes. What is the length of the half-life of this reaction

41 min

Consider the reaction at 25C: 2N2O5(g) <> 4NO2(g) + O2(g) at 25C (lists H and S)..... calculate the S for the reaction

453.72 J/K

Kc = 7.3x10^18 for the decomposition of water at 1000 C. 2H2(g) <> 2H2(g) + O2(g). If the initial H2O concentration was 0.100M, what is the concentration of hydrogen gas at equilibrium?

5.27x10^-7

Determine the equilibrium constant for the system N2O4 <> 2NO2 ar 25C. The concentrations at equilibrium are [N2O4] = 3.30x10^-2M, [NO2} = 1.41x10^-2M

6.02x10^-3

A 18.3 g piece of aluminum (which has a molar heat capacity of 24.03 J/C mol) is heated to 82.4 C and dropped into a calorimeter containing water (specific heat capacity of water is 4.18 J/gC) initially at 22.3 C. The final temperature of the water is 25.8C. Calculate the mass of water in the calorimeter.

63.1 g

For a certain process at 355 K, G = -12.2 kJ and H = -9.2 kJ. Therefore, S for the process is:

8.5 J/Kmol

The pH of a solution at 25 C in which [OH-]= 3.30x10^-5 M is:

9.52

The standard molar free energies of formation of NO2(g) and N2O4(g) at 25C are 51.840 and 98.061 kJ/mol, respectively. What is the value of Kp for the reaction below at 25C? (2NO2 <> N2O4

9.66

What is the difference between a strong acid and a weak acid?

A strong acid completely ionizes in solution while a weak acid does not

For the reaction aA > Products, use the following choices a. zero order in A b. first order in A c. second order in A d. third order in A A plot of [A] vs. t is a straight line

a. zero order in A

For the reaction aA > Products, use the following choices a. zero order in A b. first order in A c. second order in A d. third order in A A plot of ln[A] is a straight line

b. first order in A

Consider the following specific heats of metals: (lists metals) If the same amount of heat is added to 25.0 g of each of the metals, which are all at the same initial temperature, which metal will have the highest final temperature?

bismuth

2C(s) + H2O(g) <> 2CO(g) + H2O(g) An equilibrium mixture of the reactants for this exothermic reaction is placed in a sealed container at 150 C. The amount of products may be increased by which of the following changes?

both a and d (increasing the volume of the container only and decreasing the temperature of the container only)

For the reaction aA > Products, use the following choices a. zero order in A b. first order in A c. second order in A d. third order in A A plot of 1/[A] vs. t is a straight line

c. second order in A

Additional Cl2(g) is injected into the system at equilibrium : PCl5(g) <> PCl3(g) + Cl2(g) Which of the following graphs best shows the rate of the reverse reaction as a function of time?

graph with the largest straight line up, and ends above where it started

NO2(g) <> 2NO(g) + O2(g) The above materials were sealed in a flask and allowed to come to equilibrium at a certain temperature. A small quantity of O2(g) was added to the flask, and the mixture was allowed to return to equilibrium at the same temperature. Which of the following has increased over its original equilibrium value?

the quantity of NO2(g) present

A solution in which the pOH is 12.3 would be described as:

very acidic

At the normal body temperature of a human, 37 C, the equilibrium constant for the dissociation of water is higher than it is at 25 C, as shown in the equilibrium expression Kw= [H+][OH+]=2.42x10^-14

water is neutral because the hydrogen and hydroxide ion concentrations are equal