Chem 40S Final Exam Review

1. A chemist mixes aqueous solutions of radium chloride and sodium sulphate.a. Give the balanced molecular equation.

b. Give the balanced total ionic equation?

c. Give the balanced net ionic equation?

d. What are the spectator ions?

2. A chemist starts working in a new lab and finds some unlabelled bottles of aqueous solutions that are different colours. How might he distinguish between the following possibilities?

a. Iron (II) and Iron (III)

b. Copper (I) and Copper (II)

c. Cobalt (II) and Copper (II)

3. Examine the following double displacement reactions and specify whether or not it produces a precipitate (circle the correct response). If it does produce a precipitate identify it.

a. RbCl (aq) + Cu2SO4 (aq)

Precipitate: ____________________ No Precipitate

b. CoBr3 (aq) + K2S(aq)

Precipitate: ____________________ No Precipitate

c. Cr(NO3)3 (aq) + FeSO4 (aq)

Precipitate: ____________________ No Precipitate

4. A neutralization occurs between aqueous solutions of sulphuric acid and lithium hydroxide.

a. Write the balanced molecular equation

b. What is the salt produced by the reaction? _________________________

c. What is the mole ratio between sulphuric acid and water? _____:_____

d. If 3.56 moles of sulphuric acid were completely neutralized how many moles of lithium hydroxide were neutralized?

e. If 2.987 moles of lithium hydroxide were neutralized how many moles of water were produced?

f. If 2.111 moles of lithium hydroxide were neutralized how many grams of water were produced?

5. A chemist wants to find the concentration of a lithium hydroxide with an aqueous solution of sulphuric acid (1.000 mol/L). He carries out 5 titrations on 25.00 mL samples of the sulphuric acid using the lithium hydroxide solution and obtains the following data:

Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Avg.LiOH (mL) 23.39 23.35 23.45 23.40 23.41

a. What is the average volume of LiOH needed to neutralize 25.00 mL of the sulphuric acid solution.

___________________

b. How many moles of sulphuric acid are there in 25.00 mL of the sulphuric acid solution?

c. How many moles of lithium hydroxide are there in the average volume obtained in the trials?

d. What is the concentration of the lithium hydroxide solution?

e. How many significant figures should there be in your final concentration answer?

___________

f. If the chemist wants to repeat the titration with a more dilute solution of sulphuric acid. How much of the first solution should be measured out in order to obtain 2.50 L of 0.100 mol/L sulphuric acid?

6. Answer true/false for the following

Historically oxidation was defined as the loss of oxygen atoms from the oxidized substance.Historically reduction was defined as the gain of oxygen atoms by the reduced substance.A modern definition for oxidation is the gain of electrons by the oxidized substance.A modern definition for reduction is the gain of electrons by the reduced substance.

7. Assign oxidation numbers to the following:

Ag2S

Ag = _____S = ______

O2

O = _____

C2O42-

C = _____O = _____

CuF2

Cu = _____F = _____

8. Consider the following reaction:

Cr2O72- + Fe2+ + H+ → Cr3+ + Fe3+ + H2O

a. What is the oxidizing agent? _____________

b. What is the reducing agent? _____________

9. Consider the following reaction:

Zn + H+ + NO3- → Zn2+ + N2 + H2O

c. Which element is oxidized? _______________

d. Which element is reduced? _______________

10. Balance the following reactions using the oxidation number method:

a. ___Cr2O72- + ___Fe2+ + ___H+ → ___Cr3+ + ___Fe3+ + ___H2O

b. ___Zn + ___H+ + ___NO3- → ___Zn2+ + ___N2 + ___H2O

11. A beam of electromagnetic radiation is directed towards a metal surface and electrons expelled from the surface of the metal are detected. Which of the following is most likely to have caused the phenomenon:

a. Red lightb. Orange Lightc. Green Lightd. Blue Lighte. Violet lightf. Ultraviolet Light

12. Max Planck proposed a solution to the problem of Black Body radiation that involved abandoning the idea of an infinite continuum of energy in favour of one in which energy is found in discrete packages. He called these

packages:________________

13. What formula did Planck propose to define these energy packets? _____________Identify the variables

14. Since the speed of light is a constant, what happens to frequency as wavelength increases?

15. What happens to wavelength as frequency decreases?

16. What has more energy (a or b)?g. Long wavelength low frequency wave

h. Short wavelength high frequency wave

17. Below is an emission spectrum for Hydrogen and a Bohr model describing its energy emissions:

violet blue green red

i. What would be the wavelength of an n=5 to n=2 emission?____________

j. Hydrogen also has emissions outside of the visible spectrum. What would be the wavelength of invisible high energy emissions?

(use the > or < symbols) wavelength () ____________nm

18. Answer true or false for the following:

Einstein invented the concept of quantised energy for the atom.

Max Plank proposed a solution for the problem of black body radiation that did not initially gain general acceptance.

De Broglie conducted experiments that supported the particle nature of electrons rather than wave nature.

Heisenberg was able to both locate electrons and determine their momentum using the mathematics of probability.

19. Which of the following is not part of the quantum model of the atom:

k. Energy of electrons is quantised into discrete energy levelsl. The position of electrons is described by probability rather than by defined

coordinatesm. Electrons exhibit the properties of both particles and wavesn. When the electrons in an atom are excited with enough energy they will

emit white lighto. Both the position and momentum of an electron cannot be determined

simultaneously

20. Which of the rules for filling orbitals is being violated here:__________________

21. Match the following by placing the number with the matching definition:

1. Hund’s Rule An electron’s position and momentum cannot be determined simultaneously

2. Aufbau Principle Only two electrons can be placed in one orbital and they must have opposite spin

3. Pauli Exclusion Principle

Electromagnetic radiation of different colours varies in effectiveness in expelling electrons when hitting the surface of a metal

4. Heisenberg Uncertainty Principle

Electrons must be added to equal energy orbitals such that all orbitals are filled with one electron before spin pairing electrons

5. Photoelectric Effect Electrons are added to lower energy orbitals first until they are filled before adding electrons to higher energy orbitals

22. Consider Cr and Cu:

a. Write their condensed or noble gas notation configurations:

b. Write their orbital diagrams

23. Consider the following orbitals. They consist of an n=1, n=2 and n=3 orbital. Label them with their principle quantum number.

24. On the periodic table below:p. Label the different blocksq. Indicate on the trend arrows whether the trend is increasing or decreasing:

i. Atomic radiusii. Ionic radius

iii. Ionization energyiv. Electronegativity

25. Which of the following are true (there may be more than one correct answer):r. Ionic radii increase going down a group because there are fewer electron-

electron repulsions when they are further apart.s. Atomic radii decrease across a period because the electrons in the valence

shell are subject to an increasing nuclear charge.t. Atomic radii decrease down a group because valence shell electrons are

shielded from the nucleus by electrons in lower energy levels.u. Ionic radii of cations are smaller than those of their respective elements.v. Ionic radii of anions are smaller than those of their respective elements.

26. Complete the following:w. Orbital energy diagrams below for Cl- and Ar

Cl- Ar

x. Sketch their relative radii:

27. Write the full sublevel notation configuration for Krypton.

28. Consider the following elements: Cs, Sb and F. Rank them from most likely to conduct electricity to least likely (use > symbol).

29. Rank the following by decreasing first ionization energy: Pb, Ge, Sn (use > symbol).

30. Use the table of electronegativities to determine the bond character of the following:

31. Draw a water molecule and indicate where the partial charges are that make its bonds polar covalent (use the convention).

32. Answer True or False for the following:Chemical kinetics is a study of the speed of chemical reactions.

Reaction rates are determined through analysis of balanced equations.

Concentration of reactants and products is performed through direct observation of their changes in molecular structureRates of reaction are generally expressed as mol/Ls or M/s

33. List five changes in a reaction that allows one to measure changes in concentration:

a. _____________________________

b. _____________________________

c. _____________________________

d. _____________________________

e. _____________________________

34. According to collision theory effective collisions between particles require both

correct orientation and sufficient ______________________________.

35. Below is a reaction for coordinate for a reaction mechanism:f. How many steps are there in the mechanism? _______________

g. Is the enthalpy positive or negative? ___________________

h. Is the reaction endothermic or exothermic? ____________________

i. Which of the following is the rate determining step?i. A-B

ii. B-Ciii. C-D

36. Consider the reaction:

j. What is the rate expression for the reaction?

k. If the rate of consumption of NH3(g) is 2.5 mol/Ls what is the rate of

production H2O (g)? ______________________

37. Draw a reaction coordinate of the endothermic reaction: CH3OH + I- CH3I + OH-

That has a transition state that is theorized to look like:

Label the following:l. Reactantsm. Productsn. Transition stateo. Activation energyp. Enthalpy of reaction

38. Given the reaction: 4HBr + O2 2H2O + 2Br2

a) Would you expect this reaction to take place in a single step? ___________________

Why or why not? ____________________________________________________

b) This reaction is thought to take place by means of the following mechanism:

Step 1: HBr + O2 HOOBr (slow)Step 2: HBr + HOOBr 2HOBr (fast)Step 3: 2HBr + 2HOBr2H2O + 2Br2 (fast)

c) Identify the two intermediates ___________________________________________

d) A catalyst is discovered which increases the rate of Step 3. How will this affect the rate

of the overall reaction? ________________________________________________

39. List 5 factors that affect the speed of a reaction:q. ________________________________r. ________________________________s. ________________________________t. ________________________________u. ________________________________

40. Consider the data table below for the following reaction:

Time (s) [N2O5] (mol/L)

[NO2] (mol/L) [O2] (mol/L)

0 0.01240 0.00000 0.00000600 0.00920 0.00640 0.003201200 0.00680 0.01120 0.005601800 0.00500 0.01480 0.007402400 0.01740 0.008703000 0.00270 0.01940 0.009703600 0.00200 0.02080 0.010404200 0.00140 0.022004800 0.00110 0.011305400 0.00080 0.02320 0.011606000 0.00060 0.02360 0.01180

v. Fill in the missing data points in the tablew. What is the average rate of N2O5 consumption from 1800 to 5400 s?

41. Below is a graph of the above data table (Question 9).

0 1000 2000 3000 4000 5000 6000 70000.00000

0.00500

0.01000

0.01500

0.02000

0.02500

Decomposition of Dinitrogen Pentoxide at 45 °C

Time (s)

Con

cen

trat

ion

(m

ol/L

)

x. What is the instantaneous rate of production of NO2 at t = 2000 s?

42. A mechanism has been proposed in which F atoms react with Thiozone (S3) as outlined below.

Step 1: F + S3 FS + S2Step 2: FS + S F + S2

a) Write the equation for the overall reaction. (Using steps 1 and 2)

_________________________________________________________

b) What is the catalyst in this reaction? _________________________________

c) Identify an intermediate in this reaction _______________________________

d) What is the molecularity of step 1? ___________________________________43. For the generalized reaction: aA + bB + cC + dD products

State a generalized rate law (use the letters m, n, p, q, r, …. for exponents):

44. Consider the following rate equation: Rate = k[A]2[B]0[C]1

Sketch graphs for the initial rate of reaction for each reactant

[A] [B] [C]

45. Below is a data table for the following reaction:

S2O8-2 + 2 I- → I2 + 2 SO4

-2

Initial [S2O8-2] (mol/L) Initial [I-] (mol/L) Initial Rate (mol/L•s)

1.00 x 10-3 0.25 x 10-3 0.26 x 10-9

1.00 x 10-3 0.50 x 10-3 0.52 x 10-9

1.00 x 10-3 1.00 x 10-3 1.04 x 10-9

2.00 x 10-3 1.00 x 10-3 4.16 x 10-9

3.00 x 10-3 1.00 x 10-3 9.36 x 10-9

4.00 x 10-3 1.00 x 10-3 16.64 x 10-9

a. What is the rate law?

b. Find the rate constant, k (show units)

c. If you have the following starting concentrations:

[S2O8-2] = 2.34x10-4 mol/L; [I-] = 2.02x10-4 mol/L, what is initial rate of the

reaction?

d. What is the order in I-? ______________________

e. What is the overall order of reaction? ______________________

46. Below is a chemical reaction and initial rate data collected for the reaction

2NO(g) + Br2 (g) → 2NOBr(g)

Below are two graphs that also represent data collected by the method of initial rates:

0.000 0.200 0.400 0.600 0.800 1.000 1.200

-7

-6.5

-6

-5.5

-5

-4.5

-4

f(x) = 2 x − 6.64539101451465

Natural Logarithm of rate of decrease in nitrogen monoxide

ln[NO]

ln(r

ate)

0 0.2 0.4 0.6 0.8 1 1.2

-7

-6

-5

-4

-3

-2

-1

0

f(x) = 5 x − 6.64539101451465

Natural Logarithm of rate of decrease in bromine

ln[Br2]

ln(r

ate)

Note the information requested below can be derived completely from the data table or in combination with the graphs

a. What is the order of the reaction with respect to NO? ____________

b. What is the order of the reaction with respect to Br2? _____________

c. What is the rate law for the reaction?

d. What is the rate constant for the reaction (show units).

47. Answer True or False for the following:Chemical equilibrium is the state of a reaction in which the reactants and products have reached constant concentrations in a closed system

For chemical equilibrium to be reached the temperature must be changing at a continuous rate.

Dynamic equilibrium occurs when the forward reaction is slower than the reverse reaction.

Equilibrium has only been reached when the concentrations of the reactants and products is the same.

In a closed system where all concentrations on the reactant side of the chemical equation (left side) are zero equilibrium can never be reached.

48. Hydrogen gas (H2) and fluorine gas (F2) are placed in a closed system with an initial concentration of 2.00 mol/L for both and allowed to form hydrogen iodide gas (HF). At equilibrium [F2]eq = 0.48 mol/L.

Fill in the ICE Table and determine the equilibrium concentrations for the system:

ICE

[H2]eq = _________________

[HF]eq = _________________

49. Write the equilibrium law equation for the following reactions:

a.

b.

c.

d.

50. Consider the following system:

e. Find the equilibrium constant K for the forward reaction:

K = _______________________

51. Find the value of K for the reverse reaction for the system in question 4 (express in scientific notation).

K = ________________________

52. Consider the following equilibrium constants and indicate what the equilibrium will favour :

a. K = 3.3x1091 reactants / products / neither

b. K = 3.3x10-91 reactants / products / neither

c. K = 1.0: reactants / products / neither

53. Consider the following equilibrium:

Predict the direction the equilibrium will shift under the following circumstances:

a. CH3COOH is added: Shifts ________________

b. HCl is added: Shifts ______________________

c. The temperature is increased: Shifts _________________

d. The temperature is decreased: Shifts _________________

54. Consider the following equilibrium:

a. If the volume is decreased what direction will the reaction shift: left / right

b. If the volume is increased what direction will the reaction shift: left / right

c. If the reaction is endothermic and the temperature is increased what direction will he

equilibrium shift: right / left

55. A chemist places a mixture of 2.00 mol hydrogen gas, H2(g); 1.00 mol of nitrogen gas, N2(g); and 2.00 mol of ammonia gas, NH3(g), in a sealed, rigid 1.00 L flask at 750K. The equilibrium constant under these conditions is K = 1.05 x 1021.

a. Write the balanced chemical equation for the synthesis of ammonia gas.

b. Calculate the reaction quotient Q from the initial concentrations

Q = _______________

c. Is the system at equilibrium? If not what direction will the equilibrium shift?

56. Consider the following reaction:

At 500 °C, K= 16.64

A reaction was set up with the following initial concentrations: [NH3(g)]initial = 2.00x10-4 mol/L[N2(g)]initial = 1.50x10-5 mol/L[H2(g)]initial = 3.54x10-1 mol/L

a. Calculate the reaction quotient Q from the initial concentrations

Q = _______________

b. Is the system at equilibrium? If not what direction will the equilibrium shift?

57. Consider the following equilibrium:

K = 49.5

Initial Concentrations are: [H2(g)]initial = [I2(g)]initial = 0.200 mol/L; [HI(g)]initial = 0

Find the equilibrium concentrations:

ICE

[H2(g)]eq = [I2(g)]eq = ___________________

[HI(g)]eq = ____________________________

58. Consider the following equilibrium:

At T = 2000 °C, K = 6.40 x 10-7

Initial Concentrations are: [CO2(g)]initial = 0.250 mol/L; [CO(g)]initial = [O2(g)]initial = 0

Find the equilibrium concentrations:

ICE

[CO2(g)]eq = __________________

[CO(g)]eq = ___________________

[O2(g)]eq = ____________________

59. Consider the following equilibrium:

At T = 55 °C, K = 1.15

Initial Concentrations are: [NO2(g)]initial = 0.850 mol/L; [N2O4(g)]initial = 0

Find the equilibrium concentrations:

ICE

[NO2 (g)]eq = ________________

[N2O4 (g)]eq = _______________

60. What is an Arrhenius acid?61. What is an Arrhenius base?62. What is a Bronsted-Lowry Acid?63. What is a Bronsted-Lowery Base?64. What is a Lewis Acid?65. What is a Lewis Base?66. What is an amphoteric molecule?67. What is a conjugate acid?68. What is a conjugate base?69. Show the reaction between ammonium and carbonate anion and identify the

conjugate acid and base pairs.70. Show a generic acid base reaction using the symbols HA and to represent

the reaction and identify the conjugate acid base pairs.71. What is stronger an acid or its conjugate base?72. Give an example of an Arrhenius acid’s ionization.73. Give an example of an Arrhenius base’s ionization.74. Give an example of Bronsted acid that is not consistent with the Arrhenius

definition.75. Give an example of a Bronsted base that is not consistent with the Arrhenius

definition.76. Give an example of a Lewis acid-Base pair that is not consistent with the

Bronsted definition. Draw it.77. Show how water can act as both a lewis acid and base.78. Write a chemical equation to represent the self ionization of water. Then write its

equilibrium law equation.79. What is a hydronium ion?80. What is Kw at 25 °C?81. If [H+] = 4.0x10−8 mol/L what is [OH-]? Is the solution acidic or basic?82. Define pH with an equation.83. Find the pH for a solution in which [H+] = 4.0x10−8 mol/L. Is the solution acidic

or basic?84. What is pOH?85. If a solution has a pOH of 5 what is its pH?86. If a solution has a pOH of 14 is it acidic or basic?87. When is a solution neutral define in terms of both [H+] [OH-] and pH pOH?88. When a strong acid dissociates in water what is the hydronium concentration

equal to?89. List the strong acids you are expected to know.90. If 0.500 moles of HCl are dissolved in 2.00 L of water:

a. What is the pHb. What is the pOHc. What is [OH-]

91. Define percent ionization using a generic acid base equation.92. What is the percent ionization of a 0.15 mol / L HF solution whose pH is

measured to be 2.00?

93. What is Ka? Write a generic chemical equation and then the equilibrium law equation.

94. What is Kb? Write a generic chemical equation and then the equilibrium law equation.

95. Calculate the acid ionization constant of acetic acid if a 0.10 mol / L solution at equilibrium at 25°C has a percent ionization of 1.3%.

96. If Ka = 1.76x10-5 for a monoprotic acid (ie only releases one proton when it dissociates), calculate [H+] and pH for a 0.155 mol/L solution.

97. You measure the pH of a 0.25 mol/L nitrous acid (HNO2 ) solution and find it to be 2.009. What is the Ka for nitrous acid?