Review Ch 11,12 and 13

REVIEW CH 11,12 AND 13

A solution of hydrogen peroxide is 30.0% H2O2 by mass and has a density of 1.11 g/cm3. The molarity of the solution is:

2. Calculate the molality of C2H5OH in a water solution that is prepared by mixing 50.0 mL of C2H5OH with 100.0 mL of H2O at 20°C. The density of the C2H5OH is 0.789 g/mL at 20°C.

3. What is the molality of a solution of 50.0 g of propanol (CH3CH2CH2OH) in 152 mL water, if the density of water is 1.00 g/mL?

4. A solution containing 292 g of Mg(NO3)2 per liter has a density of 1.108 g/mL. Calculate the molality.

5. How many milliliters of 18.4 M H2SO4 are needed to prepare 600.0 mL of 0.10 M H2SO4?

6. A 3.140 molal solution of NaCl is prepared. How many grams of NaCl are present in a sample containing 3.000 kg of water?

7. Rank the following compounds according to increasing solubility in water.

I. CH3–CH2–CH2–CH3

II. CH3–CH2–O–CH2–CH3

III. CH3–CH2–OH

When 0.800 g of NH4NO3 was added to 150.0 g of water in a Styrofoam cup, the temperature dropped by 0.413°C. The heat capacity of H2O is 4.18 J/g°C. Assume the specific heat of the solution equals that of pure H2O and that the calorimeter neither absorbs nor leaks heat. The molar heat of solution of solid NH4NO3 is what?
The lattice energy of NaI is 686 kJ/mol and its heat of solution is –7.6 kJ/mol. Calculate the hydration of energy of NaI(s)

10. The solubility of O2 in water is 0.590 g/L at an oxygen pressure of 15 atm. What is the Henry’s law constant for O2 (in units of L-atm/mol)?

11. At a given temperature, you have a mixture of benzene (vapor pressure of pure benzene = 745 torr) and toluene (vapor pressure of pure toluene = 290. torr). The mole fraction of benzene in the solution is 0.590. Assuming ideal behavior, calculate the mole fraction of toluene in the vapor above the solution.

The vapor pressure of water at 25.0°C is 23.8 torr. Determine the mass of glucose (molar mass = 180 g/mol) needed to add to 500.0 g of water to change the vapor pressure to 23.1 torr.
At 40°C, heptane has a vapor pressure of 92.0 torr and octane has a vapor pressure of 31.2 torr. Assuming ideal behavior, what is the vapor pressure of a solution that contains twice as many moles of heptane as octane?

14. A solution is prepared from 31.8 g of a nonvolatile, nondissociating solute and 85.0 g of water. The vapor pressure of the solution at 60˚C is 142 torr. The vapor pressure of water at 60°C is 150. torr. What is the molar mass of the solute?

15. You dissolve 2.0 g of solid MX in 250. g of water. You find the freezing point to be –0.028°C. Calculate the Ksp of the solid.

16. You have a 10.40-g mixture of table sugar (C12H22O11) and table salt (NaCl). When this mixture is dissolved in 150. g of water, the freezing point is found to be –2.24°C. Calculate the percent by mass of sugar in the original mixture.

Thyroxine, an important hormone that controls the rate of metabolism in the body, can be isolated from the thyroid gland. If 0.455 g of thyroxine is dissolved in 10.0 g of benzene, the freezing point of the solution is 5.144°C. Pure benzene freezes at 5.444°C and has a value for the molal freezing point depression constant of Kf of 5.12°C/m. What is the molar mass of thyroxine?
A cucumber is placed in a concentrated salt solution. What will most likely happen?

19. Polyethylene is a synthetic polymer or plastic with many uses. 1.40 g of a polyethylene sample was dissolved in enough benzene to make 100. mL of solution, and the osmotic pressure was found to be 1.86 torr at 25°C. What is the molar mass of the polyethylene?

The observed van’t Hoff factor for an electrolyte is less than the expected factor because of ______.

21. The average rate of disappearance of ozone in the reaction 2O3(g) ® 3O2(g) is found to be 9.00 ´ 10–3 atm over a certain interval of time. What is the rate of appearance of O2 during this interval?

22. The balanced equation for the reaction of bromate ion with bromide in acidic solution is given by:

BrO+ 5Br– + 6H+ ® 3Br2 + 3H2O

At a particular instant in time, the value of –D[Br–]/Dt is 2.0 ´ 10–3 mol/L × s. What is the value of D[Br2]/Dt in the same units?

23. Consider the reaction 2H2 + O2 ® 2H2O

What is the ratio of the initial rate of the appearance of water to the initial rate of disappearance of oxygen?

Consider the following rate law: Rate = k[A]n[B]m

How are the exponents n and m determined?

The following data were obtained for the reaction of NO with O2. Concentrations are in molecules/cm3 and rates are in molecules/cm3 × s.

[NO]0 [O2]0 Initial Rate

1 ´ 1018 1 ´ 1018 2.0 ´ 1016

2 ´ 1018 1 ´ 1018 8.0 ´ 1016

3 ´ 1018 1 ´ 1018 18.0 ´ 1016

1 ´ 1018 2 ´ 1018 4.0 ´ 1016

1 ´ 1018 3 ´ 1018 6.0 ´ 1016

Give the rate law.

24. Tabulated below are initial rate data for the reaction

2Fe(CN)63– + 2I– ® 2Fe(CN)64– + I2

Initial

Run [Fe(CN)63–]0 [I–]0 [Fe(CN)64–]0 [I2]0 Rate (M/s)

1 0.01 0.01 0.01 0.01 1 ´ 10–5

2 0.01 0.02 0.01 0.01 2 ´ 10–5

3 0.02 0.02 0.01 0.01 8 ´ 10–5

4 0.02 0.02 0.02 0.01 8 ´ 10–5

5 0.02 0.02 0.02 0.02 8 ´ 10–5

Give the Rate Law.

25. The rate expression for a particular reaction is rate = k[A][B]2. If the initial concentration of B is increased from 0.1 M to 0.3 M, the initial rate will increase by what factor?

27–30. The following questions refer to the gas-phase decomposition of ethylene chloride.

C2H5Cl ® products

Experiment shows that the decomposition is first order.

The following data show kinetics information for this reaction:

Time (s) ln [C2H5Cl] (M)

1.0 –1.625

2.0 –1.735

26. What is the rate constant for this decomposition?

27. What was the initial concentration of the ethylene chloride?

28. What would the concentration be after 5.0 seconds?

29. What is the time to half-life?

30. For which order reaction is the half life of the reaction proportional to 1/k (k is the rate constant)?

31. The reaction

2A + B ® C

has the following proposed mechanism:

Step 1: A + B D (fast equilibrium)

Step 2: D + B ® E

Step 3: E + A ® C + B

If step 2 is the rate-determining step, then the rate of formation of C should equal:

a) k[A]

b) k[A]2[B]

c) k[A]2[B]2

d) k[A][B]

The reaction 2NO + O2 ® 2NO2 obeys the rate law

– = kobsd[NO]2[O2].

Which of the following mechanisms is consistent with the experimental rate law?

a) NO + NO ® N2O2 (slow)
N2O2 + O2 ® 2NO2 (fast)

b) NO + O2 NO3 (fast equilibrium)
NO3 + NO ® 2NO2 (slow)

c) 2NO N2O2 (fast equilibrium)
N2O2 ® NO2 + O (slow)
NO + O ® NO2 (fast)

d) O2 + O2 ® O2 + O2 (slow)
O2 + NO ® NO2 + O (fast)
O + NO ® NO2 (fast)

e) none of these

32. The reaction 2H2O2 ® 2H2O + O2 has the following mechanism:

H2O2 + I– ® H2O + IO–

H2O2 + IO– ® H2O + O2 + I–

The catalyst in the reaction is:

a) H2O

b) I–

c) H2O2

d) IO–

33. When ethyl chloride, CH3CH2Cl, is dissolved in 1.0 M NaOH, it is converted into ethanol, CH3CH2OH, by the reaction

CH3CH2Cl + OH– ® CH3CH2OH + Cl–

At 25°C the reaction is first order in CH3CH2Cl, and the rate constant is 1.0 ´ 10–3 s–1. If the activation parameters are A = 3.4 ´ 1014 s–1 and Ea = 100.0 kJ/mol, what will the rate constant be at 40.°C?

a) 6.9 ´ 10–3 s–1

b) 1.7 ´ 102 s–1

c) 5.0 ´ 10–3 s–1

d) 2.0 ´ 10–3 s–1

e) 5.0 ´ 1014 s–1

34. The rate law for a reaction is found to be Rate = k[A]2[B]. Which of the following mechanisms gives this rate law?

I. A + B E (fast)
E + B ® C + D (slow)

II. A + B E (fast)
E + A ® C + D (slow)

III. A + A ® E (slow)
E + B ® C + D (fast)

a) I

b) II

c) III

d) two of these

e) none of these

35. Which of the following statements concerning equilibrium is not true?

a) A system that is disturbed from an equilibrium condition responds in a manner to restore equilibrium.

b) Equilibrium in molecular systems is dynamic, with two opposing processes balancing one another.

c) The value of the equilibrium constant for a given reaction mixture is the same regardless of the direction from which equilibrium is attained.

d) A system moves spontaneously toward a state of equilibrium.

e) The equilibrium constant is independent of temperature.

36. Apply the law of mass action to determine the equilibrium expression for
2NO2Cl 2NO2 + Cl2

a) 2[NO2][Cl2]/2[NO2Cl]

b) 2[NO2Cl]/2[NO2][Cl2]

c) [NO2Cl]2/[NO2]2[Cl2]

d) [NO2]2[Cl2]/[NO2Cl]2

e) [NO2Cl]2[NO2]2[Cl2]

37. Determine the equilibrium constant for the system N2O4 2NO2 at 25°C. The concentrations are shown here: [N2O4] = 9.43 ´ 10–2 M, [NO2] = 1.41 ´ 10–2 M

a) 0.150

b) 6.69

c) 474

d) 0.0224

e) 0.00211

38. Consider the gaseous reaction CO(g) + Cl2(g) COCl2(g). What is the expression for Kp in terms of K?

a) K(RT)

b) K/(RT)

c) K(RT)2

d) K/(RT)2

e) 1/K(RT)

39. Consider the following reaction: CS2(g) + 4H2(g) CH4(g) + 2H2S(g)
The equilibrium constant K is 0.28 at 900.°C. What is Kp at this temperature?

a) 5.0 ´ 10–5

b) 4.0 ´ 10–5

c) 3.0 ´ 10–5

d) 2.0 ´ 10–5

e) 1.0 ´ 10–5

40. A 10.0-g sample of solid NH4Cl is heated in a 5.00-L container to 900°C. At equilibrium the pressure of NH3(g) is 1.20 atm.

NH4Cl(s) NH3(g) + HCl(g)

The equilibrium constant, Kp, for the reaction is:

a) 1.20

b) 1.44

c) 2.40

d) 31.0

e) none of these

41. At a certain temperature K for the reaction

2NO2 N2O4

is 7.5 liters/mole. If 2.0 moles of NO2 are placed in a 2.0-liter container and permitted to react at this temperature, calculate the concentration of N2O4 at equilibrium.

a) 0.39 moles/liter

b) 0.65 moles/liter

c) 0.82 moles/liter

d) 7.5 moles/liter

e) none of these

42. Consider the following reaction:

2HF(g) H2(g) + F2(g) (K = 1.00 ´ 10–2)

Given 1.00 mole of HF(g), 0.328 mole of H2(g), and 0.750 mole of F2(g) are mixed in a 5.00-L flask, determine the reaction quotient, Q.

a) Q = 0.0492

b) Q = 0.246

c) Q = 0.0615

d) Q = 2.08

e) none of these

43. The equilibrium system 2A 2B + C has a very small equilibrium constant:
K = 2.6 ´ 10–6. Initially 3 moles of A are placed in a 1.5-L flask. Determine the concentration of C at equilibrium.

a) 0.011 M

b) 0.022 M

c) 0.033 M

d) 0.044 M

e) 2.0 M

44. Consider the reaction represented by the equation

N2(g) + 3H2(g) 2NH3(g).

What happens to the equilibrium position when an inert gas is added to this system (as represented above) at equilibrium?

a) If the container is rigid, nothing happens to the equilibrium position. If the container is fitted with a moveable piston, the equilibrium position shifts.

b) If the container is rigid, the equilibrium position shifts. If the container is fitted with a moveable piston, nothing happens to the equilibrium position.

c) The equilibrium position shifts no matter what the container is like.

d) Nothing happens to the equilibrium position no matter what the container is like.

e) The value of the equilibrium constant must be known to answer this question