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Chemistry 120 Exam 1 Name __________________February 23, 2007

SHOW YOUR WORK. NO WORK, NO CREDIT INCLUDE LABELS AND PROPER NUMBER OF SIG FIGS

Up to 75% of the credit for a problem will be given for correctly setting it up, including labels on all numbers.

IONS Soluble/Insoluble ExceptionsGroup I metals and NH4

+ soluble noneNitrates, Acetates, Perchlorates soluble noneFluoride soluble Group IIChlorides, Bromides, and Iodides soluble silver, lead, mercury(I)Sulfates soluble strontium, barium, leadOther anions insoluble Group I and ammonium salts,

Group II sulfides, barium oxide & hydroxide,strontium oxide & hydroxide

AX2 linear AX5 trigonal bipyramid AX6 octahedralAX3 trigonal planar AX4E see saw AX5E square pyramidAX2E bent AX3E2 T AX4E2 square planarAX4 tetrahedral AX2E3 linear AX3E3 TAX3E trigonal pyramid AX2E4 linearAX2E2 bent

Enthalpies of Formation (∆Hf) for Selected SpeciesC10H22 (l) -59.67 kJ/mole HC2H3O2 (l) -484.5 kJ/mole CO (g) -110.5 kJ/moleC3H8 (g) -105 kJ/mole H2O (g) -241.8 kJ/mole CO2 (aq) -413.8 kJ/moleC6H6 (l) +49.0 kJ/mole H2O (l) -285.8 kJ/mole CO2 (g) -393.5 kJ/moleC6H12O6 -1260 kJ/mole H2O2 (l) -187.8 kJ/mole O (g) +249.2 kJ/moleCH3OH (l) -238.7 kJ/mole NH3 (g) -46.1 kJ/mole O2 (g) 0 kJ/moleC2H5OH (l) -277.7 kJ/mole NH3 (aq) -80.3 kJ/mole O3 (g) +143 kJ/mole

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I PLEDGE ON MY HONOR THAT DURING THE EXAM I HAVE NEITHER GIVEN NORRECEIVED ASSISTANCE NOR HAVE I SEEN ANY DISHONEST WORK.

Signed __________________________________________________________________________If you feel you can’t sign this, contact the instructor (e-mail or in person)

Multiple choice - circle the correct answer.1. (2 pt) What symbol (metric system prefix) is used to represent the factor 10-12?

a) n b) µ c) p d) m

2. (2 pt) Which of the following elements has chemical properties similar to aluminum?

a) boron (B) b) silicon (Si) c) phosphorus (P) d) sulfur (S)

3. (2 pt) What is the charge on the Hg in Hg2SO4?

a) -2 b) -1 c) +1 d) +2

4. (2 pt) Give the molecular formula corresponding to the following ball-and-stick molecular representation (structural formula) ofnaphthalene (black = C, white = H). In writing the formula, list the atoms in alphabetical order.

a) C10H8 b) CH c) C5H4 d) C10H10

5. (2 pt) Which of the following represent isotopes ([ ]represents the symbol for the designated atom) ?

3479 []

A3579 []

B3478[]C

3681[]D

a) C and D b) A and D c) A and B d) A and C

6. (2 pt) Which of the drawings represents a mixture?

(a) (b) (c)

a) (a) b) (b) c) (c) d) none of them

7. (2 pts) How many orbitals are there in the n = 2 shell (second shell)?

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a) 2 b) 4 c) 6 d) 8

8. (2 pt) 8.0 mole of iron is reacted with 8.0 mole of water according to the chemical equation shown below. Which one of the followingstatements is false?

3 Fe (s) + 4 H2O (l) ! Fe3O4 (s) + 4 H2 (g)

a) no Fe is left over b) mass is conserved in the reaction

c) 2 mole of Fe3O4 are produced d) water is the limiting reagent

9. (2 pt) Which subatomic particle has the smallest mass?

a) an electron b) a neutron c) a proton d) all three have the same mass

10. (2 pt) All of the following elements are nonmetals except

a) hydrogen b) carbon c) arsenic d) oxygen

11. (2 pt) Which grouping of elements, indicated by letter on the periodic table at the right,represents the d-block elements?

a) A b) B c) C d) D

12. (2 pt) How many significant figures are there in the answer for the following problem? 63.1 + 21.5588 + 37 = ?

a) 1 b) 2 c) 3 d) 4

13. (2 pt) Iodine (53I) belongs to which group of the periodic table?

a) alkaline earth metals b) halogens c) alkali metals d) noble gases

14. (2 pt) Which of the following numbers has the least number of significant figures?

a) 410000 b) 0.50700 c) 6.022 x 1023 d) 0.000201

15. (2 pt) To the correct number of significant figures, what is the volume in the graduated cylinder?

___________________________

16. (2 pts) If SeO4-2 is called selenate, what is the formula for hyposelenite?

17. (3 pts) Write the formula of the compound that results when BiO+1 combines with Fe(CN)6-4.

18. (3 pts each) Name the following compounds: SO2, Cu3(PO3)2, SrBr2.

19. (3 pts each) Write the formula for each of the following compounds.a. potassium periodateb. monobromine dioxidec. tin (II) hydroxide

20. (6 pts) In lab the class is running a series of reactions that use several potentially hazardous chemicals. Groups are working on thelab benches and are scattered throughout the lab (typical situation for our lab). Your group has finished the experiment earlier thanthose groups around you. Is it OK for your group to remove your safety goggles to work on calculations at your lab desk while theothers finish the lab? Explain your reasoning.

21. (9 pts) The wavelength of infrared light used in a particular remote control is 1.2 µm. What is the energy of one photon of thisradiation?

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0 5 10 15Time (ms )

(a)

(b)

22. (9 pts) What is the mass percent of oxygen in K3AsO4?

23. (9 pts) How many atoms of carbon are there in 100 kL of ethanol (C2H5OH)? The density of ethanol is 0.789 g/mL.

24. Baking soda (NaHCO3) neutralizes battery acid (H2SO4) in aqueous solution by the following reaction:NaHCO3 + H2SO4 ! Na2SO4 + H2CO3

a. (5 pts) Balance the reaction. b. (9 pts) When excess NaHCO3 was added to 100.0 mL of 0.100 M H2SO4, 5.0 x 10-3 mole of H2CO3 was actually recovered. What

was the percent yield for this reaction?

Chemistry 120 Exam 2 Name __________________March 16, 2007

Circle the correct answer:

1. (2 pts) Which one of the following ionic compounds is soluble in water?

a) Ag3PO4 b) ZnCO3 c) NH4ClO2 d) CuS

2. (2 pts) The spheres below represent atoms of Co, Al, P, Ar (not necessarilyin that order). Which one of these spheres represents an atom of P?

a) sphere a b) sphere b c) sphere c d) sphere d

3. (2 pts) Which of the following elements is a liquid at room temperature?

a) iodine b) fluorine c) bromine d) chlorine

4. (2 pts) An element that has the valence electron configuration 2s22p4 belongs to which period and group?

a) period 4, group 2 b) period 2, group 6 c) period 6, group 2 d) period 2, group 45. (2 pts) Which of the following elements has the highest first ionization energy?

a) Cs b) K c) Sr d) Ba

6. (2 pts) Identify the fourth-row element X that forms the ion on the right.

a) As b) Kr c) Se d) Ga

7. (2 pts) How many subshells are there in the shell with n = 6?

a) 36 b) 4 c) 5 d) 6

8. (2 pts) Which of the following ionic compounds is not soluble in water?

a) NaOH b) CuCl2 c) BaSO4 d) CaS

9. (2 pts) Which statement is true for the two electromagnetic waves represented at the right? Thex-axis scale is the same for both waves.

a) Wave (b) has a higher frequency and higher energy than wave (a).

b) Wave (b) has a higher frequency and lower energy than wave (a).

c) Wave (b) has a lower frequency and higher energy than wave (a).

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HNH

H

IBr

Br

Br HSe H

CH

HO

U FF

FF

FF

d) Wave (b) has a lower frequency and lower energy than wave (a).

10. (2 pts) What is the H-N-H bond angle in NH3 (Lewis structure shown) ?

a) about 120° b) about 109.5° c) about 90° d) about 180°

11. (2 pts) Which atom or ion has the smallest radius?

a) Cl-1 b) Kr0 c) Rb+1 d) Sr+2

12. (2 pts each) Name the following compounds.a. (NH4)2CrO4b. SnSO3

13. (2 pts each) Write the formula for each of the following compounds.a. ammonium acetateb. dichlorine heptoxide

14. (6 pts) Label the following binary compounds as ionic, polar covalent, or purely covalent. Then explain your reasoning.

HCl ______________ LiI ______________ O2 ______________

15. (8 pts) Write the electron configuration for 76Os. You may start with an inert gas core if you wish.

16. (7 pts each) Draw Lewis structures, including any resonance forms, for: ClO2+1 and RnF4.

17. (1 pt each) Fill in the blanks for each structure

Molecular Shape _______________________

Polar (yes/no)? _______________________

Molecular Shape _______________________

Polar (yes/no)? _______________________

Molecular Shape _______________________

Polar (yes/no)? _______________________

Molecular Shape _______________________

Polar (yes/no)? _______________________

18. (7 pts) The electron configuration for 41Nb is [Kr] 5s2 4d3. Is +3 expected to be a stable charge for Ru? Explain your reasoning.

19. (7 pts) Which Lewis Structure below cannot exist as a real molecule? Explain your reasoning.

IBr

Br

BrCl

Br

Br

Br FBr

Br

Br

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AX2 AY2 AZ2

20. While in lab, your lab partner accidentally slops 10 mL of 1 M HCl onto your bare arm. a. (3 pts) What action should you take? b. (3 pts) What action should your lab partner take?

21. (7 pts) What is the molar concentration of sodium ions in a 0.350 M Na3PO4 solution?

22. (7 pts) The figure on the right shows the resonance structures for cyanate ion(CNO 1). Use formal charges to identify the better (more important)structure(s)? Explain your reasoning.

Chemistry 120 Exam 3 Name __________________April 16, 2007

Circle the correct answer.

1. (2 pts) The reaction of Pb(NO3)2 + K2SO4 ! PbSO4 + 2 KNO3 is best classified as a(n)

a) precipitation reaction b) acid base reaction c) redox reaction d) none of the above

2. (2 pts) The reaction of 2 HNO3 + Ba(OH)2 !Ba(NO3)2 + 2 H2O is best classified as a(n)

a) precipitation reaction b) acid base reaction c) redox reaction d) none of the above

3. (2 pts) Which is the balanced net ionic equation for the reaction of Pb(NO3)2 with NaI.

a) NO3-1 + Na+1 ! NaNO3 b) Pb(NO3)2 + 2 NaI ! PbI2 + 2 NaNO3

c) Pb+2 + 2 NO3-1 + 2 Na+1 + 2 I-1 ! PbI2 + 2 NaNO3 d) Pb+2 + 2 I-1 ! PbI2

4. (2 pts) When Na2CrO4 (aq) and AgNO3 (aq) are mixed, a red colored precipitate forms which is

a) Ag2CrO4 b) Na2NO3 c) AgCrO4 d) NaAg

5. (2 pts) Which species functions as the reducing agent in the following reduction-oxidation reaction 2 P + 3 Br2 !2 PBr3?

a) Br-1 b) Br2 c) P+3 d) P

6. (2 pts) According to the balanced equation shown below, how many moles of MnO4-1 react with 1.00 mole of oxalic acid,

H2C2O4? 5 H2C2O4 (aq) + 2 MnO4-1 (aq) + 6 H+1 (aq) !10 CO2 (g) + 2 Mn2+ (aq) + 8 H2O (l)

a) 2.00 mole MnO4-1 b) 1.00 mole MnO4

-1 c) 0.400 mole MnO4-1 d) 2.25 mole MnO4

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7. (2 pts) Which of the following compounds is a strong base? a) H2SO4 b) NH3 c) H2O d) Na2O

8. (2 pts) Three different substances, AX2, AY2, and AZ2, weredissolved in water in separate beakers with the results shown in thediagram. (Water molecules are omitted for clarity.) Which of thesubstances is the weakest electrolyte?

a) AX2 b) AY2 c) AZ2 d) all the same

9. (2 pts) Tin occurs in two crystal forms, called white tin and grey tin. Based on the data below for the conversion of whitetin to grey tin, the conversion will be

O C N

O C N

O C N

-1 -1 -1

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Sn(white) ! Sn(gray) ∆H = -2.09 kJ/mole ∆S = -7.41 J/(K·mole)

a) spontaneous at low temperatures and nonspontaneous at high temperatures.

b) nonspontaneous at low temperatures and spontaneous at high temperatures.

c) spontaneous at all temperatures.

d) nonspontaneous at all temperatures.

10. (2 pts) Predict the products of a reaction between Ba(NO3)2 (aq) and K2SO4 (aq).

a) BaSO3 (s) and KNO2 (aq) b) BaSO4 (s) and KNO3 (aq)

c) BaSO4 (aq) and KNO3 (aq) d) Ba(SO4)2 (s) and K2NO3 (aq)

11. (2 pts) What is the change in oxidation number (charge) for the carbon in the following unbalanced oxidation half reaction?C2H6 ! C2H4O2

a) 6 b) 3 c) 4 d) no change

12. (2 pts) HBr, HI, HNO3, NaBr, and KNO3 are all classified as

a) strong acids b) strong bases c) strong electrolytes d) weak electrolytes

13. (2 pts) At constant pressure, the exothermic combustion of 0.1667 mole of C2H6 (g) releases 259.0 kJ of heat. What is ∆Hfor the reaction (below)?

2 C2H6 + 7 O2 ! 4 CO2 + 6 H2O

a) -1554 kJ/mole C2H6 b) + 1554 kJ/mole C2H6 c) + 259.0 kJ d) -259.0 kJ

14. (2 pts) A bicycle pump plunger is drawn half way and the inlet sealed at 20°C (orig.). With the piston allowed to movefreely, the temperature is increased to 50°C. Which diagram most closely represents the position of the piston at 50°C?

15. (2 pts) Which of the following compounds is a weak acid?

a) NH3 b) H2SO4 c) NaHCO3 d) CH3Cl

16. (2 pts) Which metal is the worst heat conductor (specific heat in parentheses)?

a) Al (0.90 J/g·deg) b) Cu (0.39 J/g·deg) c) Pb (0.16 J/g·deg) d) Sn (0.222 J/g·deg)

17. (2 pts each) Name the following compounds.a. H3PO2b. CoF2

18. (2 pts each) Write the formula for each of the following compounds.a. chloric acid

(d)(a) (b) (c)orig.

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b. tin (IV) cyanide

19. (8 pts) Balance the following redox reaction that takes place in acidic solution.IO4

-1 + Mn+2 ! MnO4-1 + I-1

20. (6 pts) Why are sandals not acceptable footware in a chemistry lab?

21. (8 pts) Write and balance the net ionic equation.HNO3 + Pb(ClO2)2 ! Pb(NO3)2 + HClO2

22. (8 pts) Calculate the ∆H for the reaction below using the ∆Hf values on the front page.3 C3H8 (g) + 10 O3 (g) ! 9 CO2 (g) + 12 H2O (g)

23. (8 pts) How many molecules of N2 are in a 500.0 mL container at 780 mm Hg and 135°C?

24. When 20.00 g of NH3 reacts in the presence of excess O2 according to the following chemical equation in a sealedcalorimeter,

4 NH3 (g) + 5 O2 (g) ! 4 NO (g) + 6 H2O (l) ∆H = +1168 kJ

a. (6 pts) Will the temperature inside the calorimeter increase or decrease? Explain your reasoning.b. (8 pts) In a calorimeter heat lost has to equal heat gained. How much heat will be transferred in this reaction?

25. (8 pts) When 1.000 kg of copper absorbs 2156 J of heat, it temperature rises from 25.0°C to 30.6°C. What is the specificheat of copper?

Chemistry 120 Exam 4 Name __________________May 4, 2007

1. (2 pts) When a liquid is heated at its boiling point, the

a) temperature of the liquid remains the same as long as any liquid is present. b) covalent bonds are broken, allowing vaporization to occur. c) temperature of the liquid increases. d) temperature of the vapor phase increases.

2. (2 pts) In the drawing of acetaldehyde, CH3CHO, the largest partial positive charge (δ+) occurson

a) atom (a) b) atom (b) c) atom (c) d) atom (d)

3. (2 pts) Which of the following is an ionic solid?

a) NH4Cl b) NH3 c) CH3NH2 d) Au

4. (2 pts) Which of the following substances has the highest boiling point?

a) CH3-CH2-CH3 b) Ar c) CH3-CH2-O-H d) NaF

5. (2 pts) The reaction A2 + B2 ! 2 AB has an equilibrium constant Keq = 1.8. The following pictures represent reactionmixtures that contain A2 molecules (shaded) and B2 molecules (unshaded), and AB molecules. Which reaction mixture isat equilibrium?

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a) reaction mixture (1) b) reaction mixture (2) c) reaction mixture (3) d) reaction mixture (4)

6. (2 pts) Which of the following will form an acidic solution when dissolved in water?

a) NH3 b) NaOH c) FeCl2 d) none are acidic

7. (2 pts) Iron oxide ores are reduced to iron metal by exothermic reaction with carbon monoxide (balanced reaction below).Which of the following changes in condition will cause the equilibrium to shift toward the products?

FeO (s) + CO (g) ! Fe (s) + CO2 (g)

a) add FeO b) add CO c) raise the temperature d) add CO2

8. (2 pts) In the reaction above, the unshaded spheres represent H atoms. Which of the reactants and products are acids?

a) (2) and (3) b) (1) and (3) c) (1) and (4) d) (2) and (4)

9. (2 pts) Which one of the following salts, when dissolved in water, produces the solution with the highest pH?

a) MgO b) NH3 c) NaOH d) NaCl

10. (2 pts) The following pictures represent aqueous solutions of three acids;water molecules have been omitted for clarity. Which acid has the smallestKa?

a) HX b) HY c) HZ d) all have the same Ka value

11. (2 pts) Which of the following compounds does not exhibit hydrogenbonding?

a) H2O b) HF c) H3C-O-CH3 d) CH3CH2NH3

12. (2 pts) Which should be most soluble in liquid CO2?

a) b)

c) d)

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13. (2 pts) As a liquid evaporates at a temperature below its boiling point, the temperature of the liquid

a) increases b) decreases c) stays the same d) decreases at low temperatures, but increases at high temperatures

14. (2 pts) Which picture on the right best indicates the direction of the dipole momentin formaldehyde, H2C=O?

a) (1) b) (2) c) (3) d) (4)

15. (2 pts) In pure liquid methanol, CH3OH, which intermolecular forces are present?

a) Dipole-dipole and ion-dipole forces are present.b) Dispersion, hydrogen bonding and dipole-dipole forces are present.c) Only hydrogen bonding forces are present. d) Dispersion and dipole-dipole forces are present.

16. (2 pts) One reason ionic compounds do not dissolve well in nonpolar solvents isthat

a) not all cations and anions have the same magnitude of charge and therefore do not form neutral ion pairs.b) ion-dipole interactions are too large for effective solvation to occur.c) ion-solvent interactions are not strong enough to solvate the ions in solution.d) there are no forces of attraction between ions and nonpolar molecules.

17. (2 pts) What is the equilibrium constant expression (Ksp) for the ionization of insoluble Cu(OH)2 in water?

a) Ksp = [Cu+2][OH-1]2/[Cu(OH)2] b) Ksp = [Cu+2][OH-1]2

c) Ksp = [Cu(OH)2]/([Cu+2][OH-1]2) d) Ksp = 1/[Cu+2][OH-1]2

18. (2 pts) Of these weak acids, which is the weakest?

a) HF with Ka = 3.5 x 10-4 b) HC2H3O2 with Ka = 1.8 x 10-5

c) HC7H5O2 with Ka = 6.5 x 10-5 d) HClO with Ka = 3.5 x 10-8

19. (2 pts) What statement is most consistent for an acid with a pH = 6?

a) It is twice as strong as an acid with a pH of 3.b) It is half a strong as an acid with a pH = 3c) It is one thousandth as strong an acid with a pH of 3.d) It is one thousand times as strong as an acid with a pH = 3.

20. (2 pts each) Name the following compounds.a. HBrO4b. NH3

21. (2 pts each) Write the formula for each of the following compounds.a. Potassium dihydrogen phosphiteb. Acetic acid

22. (8 pts) Write the equilibrium constant expression for the following balanced, net ionic reaction:MnO4

-1 + 5 Fe+2 + 8 H+1 W Mn+2 + 5 Fe+3 + 4 H2O

23. (6 pts) Why is it NOT a good idea to store coats and bookbags on the lab benches in lab?

24. (10 pts) Sodium hydroxide is available commercially as a 50.0% by weight aqueous solution. The density of the solutionis 1.53 g/mL. Calculate the molarity of this sodium hydroxide solution.

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25. (10 pts) When K2CO3 is dissolved in water, will the solution be acidic, basic, or neutral? Explain your reasoning, showingreactions where appropriate.

26. (10 pts) What is the pH of a 0.000250 M H2SO4 solution?

27. (10 pts) Calculate the pH for 0.500 M HCN (Ka = 4.9 x 10-10)?