Name______________________________________________ Student ID Number___________________________________ Lab Sec. # ___; TA: __________; Lab day/time: __________ Dr. Enderle Summer Session One 2016 CHEMISTRY 2C (Section A) Exam

Instructions: CLOSED BOOK EXAM! No books, notes, or additional scrap paper are permitted. All information required is contained on the exam. Place all work in the space provided. If you require additional space, use the back of the exam. A scientific calculator may be used (if it is a programmable calculator, its memory must be cleared before the exam). Read each question carefully. (1) For Parts I and II, there is no partial credit given (unless marked).

For Part I, only answers marked on this cover page will be graded. You must also fill in your TA’s name at the top of the page. Failure to do either of these will result in a 10 point deduction.

(2) The last two pages contain a periodic table and some useful information. You may remove it for easy access.

(3) If you finish early, RECHECK YOUR ANSWERS! U.C. Davis is an Honor Institution

Possible Points Points #1–12. (3 pts each) / 36

#13-14. (12 pts) / 12 #15-16. (26 pts) / 26

#17. (10 pts) / 10 #18-19. (14 pts) / 14 #20ab. (17 pts) / 17 #20cde. (12 pts) / 12

#21. (12 pts) / 12 Total Score (139) / 139

Multiple Choice (circle one) 1. a b c d e

2. a b c d e

3. a b c d e

4. a b c d e

5. a b c d e

6. a b c d e

7. a b c d e

8. a b c d e

9. a b c d e

10. a b c d e

11. a b c d e

12. a b c d e

Pt I Calcs (6 pts each)

13. a b c d e

14. a b c d e

Name: ____________________________________ Exam (Page 2 of 12)

Part I: Multiple Choice, Concepts (3 points each) Select the best answer and enter your choice on the cover sheet – No partial credit

1. Which sacrificial anode would best protect iron from corrosion?

(a) Ag (b) Pb (c) Cu (d) None of these (e) Any of these 2. Which of these is a possible definition of reduction?

(a) Gaining oxygen atoms (b) Losing hydrogen atoms (c) Increase in oxidation state (d) Electrons in reactants of a half reaction (e) Losing electrons

3. What is true of a concentration cell, where the two half cells have the same reaction? (a) ξ = 0 (b) ξ° = 0 (c) All ion concentrations are equal (d) The cell is nonspontaneous 4. Which of the following is true? (a) A dry cell battery is not rechargeable (b) Button batteries have high storage capacity allowing them to be very small (c) Car batteries contain sulfuric acid

(d) Fuel cells are 80-100% efficient (e) All are correct

5. Which statement is true? (a) The oxidation half reaction produces electrons (b) Electrons move from the cathode to the anode in a galvanic cell (c) Primary cell batteries can be recharged by applying an external voltage (d) At equilibrium, the standard cell potential (ξ°) is zero (e) Sodium metal is a strong oxidizing agent 6. What statement would not describe the molecule: [CoCl(ox)(NH3)3]?

(a) Both fac and mer geometric isomers are possible. (b) No optical isomers exist (c) The mirror image of this molecule is superimposable upon itself (d) This molecule is best described using cis and trans geometric isomers (e) One of the ligands is bidentate

7. Which d orbital is drawn on the xy axes? (a) dxy (b) dxz (c) dyz (d) dx2-y2 (e) dz2

Name: ____________________________________ Exam (Page 3 of 12)

8. Choose the incorrect statement about the electron configuration of transition elements. (a) Cu: [Ar]4s13d10 (b) Fe: [Ar]4s23d6 (c) Cr: [Ar]4s23d4 (d) V: [Ar]4s23d3

9. Metallurgy may involve which of the following processes? (a) Roasting (b) Refining (c) Electrolysis (d) Reduction (e) Any of these 10. Estimate which transition metal element would have the smallest radius?

(a) Fe (b) Re (c) Ru (d) Hg (e) Os 11. Even though sulfur is not a heavy, post-transition metal element, it follows the pattern of the inert

pair effect. Which of the following is not a likely charge of sulfur? (a) -2 (b) +1 (c) +2 (d) +4 (e) +6 12. Of the following complex ions, three appear violet in aqueous solution, one appears blue-green, and one appears yellow. Which is yellow?

(a) [Cr(H2O)6]3+ (b) [CrCl(H2O)5]2+ (c) [CrCl(NH3)5]2+ (d) [CrCl2(NH3)4]+ (e) [Cr(NH3)6]3+

Part I Continued: Multiple Choice, Calculations Select the best answer and enter your choice on the cover sheet. If you do not select the correct

answer, you may show work for up to half credit per question. 13. (6 points) How many grams of copper metal are collected by passage of 3.00 A of current for 45.0 min in the electrolysis of an aqueous solution of copper(II) ion?

(a) 0.0420 g (b) 0.0840 g (c) 2.67 g (d) 5.33 g 14. (6 points) Find ξ˚ for the reaction occurring in an electrolytic cell that uses the following half reactions:

Zn2+ (aq) + 2e- → Zn (s) Cu2+ (aq) + 2e- → Cu (s)

(a) 0.423 V (b) -0.423 V (c) 1.103 V (d) -1.103 V

Name: ____________________________________ Exam (Page 4 of 12)

Part II: Short Calculations, Fill in the Blank (No Partial Credit) 15. (14 pts) Fill in the blanks in the table below for the given molecules.

16. (12 points) Reactions: fill in the blank with the appropriate molecule(s) and balance the reactions using whole numbers. 2 NaCl →

Ca + 2 H2O →

K + H2 → Cr2O3 + 6 HCl →

Molecule Coordination Number of

Metal

Electronic Config. of

Metal (i.e., d8)

Oxidation State

of Metal

Could the molecule be

chiral?

VSEPR shape (if more than one

possible, list all)

[HgClI] 2 d10 2 no Linear (Bent ok)

Name [HgClI] = chloroiodomercury(II)

[PtCl4]2- 4 d8 2 no Tetrahedral,

Square Planar

Name [PtCl4]2- = tetrachloroplatinate(II) ion

2 Na + Cl2

Ca(OH)2 + H2

2 KH

2 CrCl3 + 3 H2O

Name: ____________________________________ Exam (Page 5 of 12)

17. (10 points) Fill in the blank: in the column marked “Answer” to the left of each statement, fill in the statement number that best describes the element or concept.

Answer Statement – Which element is it?

Ti 1. This metal is low density, high strength, and low corrosion which

makes it an excellent structural material. It has similar chemistry to C and Si. The common oxidations states are +3 and +4.

H 2. This element is the most common in the universe. It is colorless,

odorless, and tasteless. The water gas shift reaction is used industrially to form this element.

He 3. This element is naturally monoatomic and nearly unreactive because of

a filled electron shell. This element also does not experience viscosity (superfluidity). It is used as a diluent.

Ni 4. This element is doubly-magic and thus extremely stable. It is an

example on one element that forms strong bonds with CO. It is used in currency and some rechargeable batteries.

O 5. This main group nonmetal has three common oxidation states: 0, -1, and

-2. It has two common elemental forms, one of which protects us from harmful UV rays. This element is also a component of oxy acids.

B 6. This element is between a metal and nonmetal. It can form dimers as

well as various sized clusters. It has applications as a dopant in semiconductors. The common oxidation state is +3.

P 7. This main group element has several allotropes, including white and red

allotropes. It is found biologically in ADP and ATP, and produced industrially as a component in fertilizer.

W 8. This transition element, also known as Wolfram, is the only third row

element found in biomolecules. One common application is incandescent light bulbs.

Na 9. This metal is easily oxidized to form a peroxide. It is formed

industrially through the decomposition of salt.

V 10. This transition metal makes strong and tough steels. It is also a catalyst

is the production of sulfuric acid. The common oxidations states are +2 and +5.

Name: ____________________________________ Exam (Page 6 of 12)

Part III: Long Answer Please show all work for calculations – Partial credit may be given

18. (6 points) Draw the structures of all possible stereoisomers of the following molecule: bromochlorobisethylenediamineiron(III) ion. Circle chiral molecules, if any. You will lose one point for each incorrect molecule drawn.

All octahedral compounds.

1. trans 2. cis 3. cis enantiomer

19. (8 points) Draw the Lewis structure for the following compounds:

(a) Main Group compound: IF5 (mixed halogen compound)

(b) Main group compound XeO2 (Xenon compound)

Name: ____________________________________ Exam (Page 7 of 12)

20. (29 points total) A solution containing the following was prepared: 0.17 M Pb2+, 1.5 x 10-6 M Pb4+, 1.5

x 10-6 M Mn2+, 0.17 M MnO4-, and 0.92 M HNO3. For this solution, the following reaction can occur:

Pb4+ (aq) + Mn2+ (aq) → Pb2+ (aq) + MnO4- (aq),

where the standard reduction potential of lead(IV) to lead(II) is 1.69 V.

(a) (12 points) Determine ξ°, ΔG°, and K for this reaction.

Pb4+ + 2e- → Pb2+, ξ° = 1.69 V

MnO4- + 8H+ + 5e- → Mn2+ + 4H2O, ξ° = 1.51 V

ξ° = 1.69 – 1.51 = 0.18 V

ΔG°=-nFξ°=-(10mole-)(96,485C/mole-)(0.180V)=-1.74e5JK=e^[ξ°n/0.0256]=e^[(0.180V)(10mole-)/0.0256]=3.44e30

(b) (5 points) Calculate the value for the cell potential, ξ, for the given conditions.

ξ = ξ° - (0.0256/n) lnQ

𝐐 = [𝐏𝐛𝟐!]𝟓[𝐌𝐧𝐎𝟒!]𝟐[𝐇!]𝟏𝟔

[𝐏𝐛𝟒!]𝟓[𝐌𝐧𝟐!]𝟐=

𝟎.𝟏𝟕𝟓𝟎.𝟏𝟕𝟐𝟎.𝟗𝟐𝟏𝟔

(𝟏.𝟓×𝟏𝟎!𝟔)𝟓(𝟏.𝟓×𝟏𝟎!𝟔)𝟐= 𝟔.𝟑𝟐𝟔×𝟏𝟎𝟑𝟒

ξ = 0.180 – (0.0256/10)ln(6.326e34) = -0.0251 V

ξ° =

ΔG°=

K=

ξ =

Name: ____________________________________ Exam (Page 8 of 12)

(c) (1 point) Determine the value of ξ for this system at equilibrium. ξ = 0

(d) (5 points) Determine the pH at which the given concentrations of Pb2+ (aq), Pb4+ (aq), Mn2+ (aq), and

MnO4- (aq) would be at equilibrium. If you didn’t get part (a), then use 1030 for K.

𝐊 = [𝐏𝐛𝟐!]𝟓[𝐌𝐧𝐎𝟒!]𝟐[𝐇!]𝟏𝟔

[𝐏𝐛𝟒!]𝟓[𝐌𝐧𝟐!]𝟐=

𝟎.𝟏𝟕𝟓𝟎.𝟏𝟕𝟐[𝐇!]𝟏𝟔

(𝟏.𝟓×𝟏𝟎!𝟔)𝟓(𝟏.𝟓×𝟏𝟎!𝟔)𝟐= 𝟑.𝟒𝟒×𝟏𝟎𝟑𝟎

[H+] = 0.498

pH = 0.303

If solved with K=1030

[H+] = 0.461

pH = 0.336

(e) (6 points) Draw the galvanic cell using shorthand notation. Include state symbols.

Pt (s) | Mn2+ (aq), MnO4- (aq), H+ (aq) || Pb2+ (aq), Pb4+ (aq) | Pt (s)

pH =

Name: ____________________________________ Exam (Page 9 of 12)

21. (12 points total)

(a) (5 points) Draw the CFT diagram for [HgClI]. (Include an energy axis, appropriately filled

electrons, labeled orbital levels, Δ, etc.).

Draw a linear, weak field CFT diagram with 10 electrons (all paired).

(b) (5 points) Draw the tetrahedral CFT diagram for [CoCl4]2- (Include an energy axis, appropriately

filled electrons, labeled orbital levels, Δ, etc.).

Draw a tetrahedral, weak field CFT diagram with 7 electrons. There are two sets of paired

electrons and three unpaired electrons.

(c) (1 point) Which compound is paramagnetic, if any?

[CoCl4]2-

(d) (1 point) Which compound is most likely colorless, if any? [HgClI]

Name: ____________________________________ Exam (Page 10 of 12)

Name: ____________________________________ Exam (Page 11 of 12)

Constants:

R = 8.3145 J / mol K F = 96,485 C/ mol e-

R = 0.08206 L atm / mol K c = 2.9979 x 108 m / s h = 6.626 x 10-34 J s

Spectrochemical Series: CN->CO>NO2

->en>NH3>H2O>ox2->OH->F->SCN->Cl->Br->I-

Equations: ocellnFEG −=°Δ cellnFEG −=Δ

°Δ−°Δ=°Δ STHG QRTGG ln+°Δ=Δ eqKRTG ln−=°Δ

490

430

800 400

580

620

560

y

v

g

o b

r

eqocell K

nE ln0256.0

= Qn

EE ocellcell log0592.0−=

QnFRTEE o

cellcell ln−=

Name: ____________________________________ Exam (Page 12 of 12)