Last Name:_____________________________ First Name: ___________________

Lab Sec. # _______; TA: _________________________; Lab day/time: ___________

Dr. Enderle, Summer 2016

CHEMISTRY 2C (A) FINAL 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). This exam has 11 pages total. (1) Read each question carefully. (2) For Part I and Part II there is not partial credit. There is partial credit for part

III. 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.

(3) The last three pages contain a periodic table and some useful information. You may remove them for easy access.

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

Possible Points Earned Points # 1–11 (03 points each) / 33

# 12-15 (06 points each) / 24

# 16-18 (20 points total) / 20

# 19-20 (20 points total) / 20

# 21 (18 points total) / 18

# 22-23 (11 points total) / 11

# 24 (14 points total) / 14

# 25 (18 points total) / 18

# 26 (10 points total) / 10

Total Score (168) / 168

01. a b c d e

02. a b c d e

03. a b c d e

04. a b c d e

05. a b c d e

06. a b c d e

07. a b c d e

08. a b c d e

09. a b c d e 10. a b c d e

11. a b c d e

1-9 total points:

12. a b c d e

13. a b c d e

14. a b c d e

15. a b c d e

10-13 total points:

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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 nuclides are more likely stable?

a. Odd number of protons and neutrons b. Z > 83 c. Number of protons = number of neutrons, when Z > 10 d. When the number of protons and neutrons equal a magic number

2. Which of the following is true? a. Synthesis of transuranium elements may occur in a cyclotron or synchrotron b. A positron is an antiparticle of the electron c. Dark matter is hypothesized to account for the total mass of the universe d. The element Sg and Unh are the same element e. All the above 3. Find the incorrect nuclear reaction.

a. 235U92 + 1n0 → 139Ba56 + 94Kr36 + 3 1n0

b. 239Pu94 + 1n0 → 140Cs55 + 100Y39

c. 235U92 + 1n0 → 232Th90 + 4He2

d. 235U92 + 1n0 → 139Ba56 + 94Kr36 + 1n0

e. 238U92 + 1n0 → 239U92 4. Which of the following is incorrect?

a. Fission is splitting larger nuclei into smaller ones. b. Nuclear reactors use waters to keep the reactor cool. c. Depleted uranium is not useful for ammunition. d. Nuclear weapons may use fission or fusion reactions. e. Natural uranium ore must be enriched to make weapons grade uranium.

5. Choose the correct word to describe the nuclear stability of the following isotope: U-238. If it is radioactive, choose the most likely mode of decay.

a. radioactive, beta b. radioactive, fission c. radioactive, alpha d. radioactive, neutron e. stable 6. What is not an application of radiation processing? a. kill pathogens b. preserve food c. sanitize medical equipment d. make substances radioactive 7. Define "conformation".

a. Conformations are different arrangements of bonds in space b. Conformations are different structural representations of the same molecule. c. Conformations are different spatial arrangements one structure can have d. Conformations are two enantiomers. e. Conformations are all possible structural isomers for a given molecular formula

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8. A catalyst:

I) lowers activation energy II) provides an alternate reaction pathway III) is consumed in the reaction and thus does not appear in the chemical equation of each mechanism IV) increases the rate of a reaction V) is heterogeneous if it is in a different phase than the reactants

a. I, III, and IV b. I, IV, and V c. II, III, and IV d. II and IV e. I, II, IV, and V

9. According to the collision theory in gaseous molecules, collision frequency is ________ and the number of reactions is ________ because ________.

a. low, low, molecules are so far apart b. high, high, each collision results in a reaction c. low, low, molecules must collide before they can react d. high, relatively low, only a fraction of the collisions lead to a reaction e. low, high, molecules are moving so fast that each reaction causes many others

10. What is the order of reaction where the reaction rate is constant?

a. 0 b. 1 c. 2 d. 3 11. Which of the following reaction profiles (figure below) would be the most favored kinetically?

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

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Part I Continued: Multiple Choice, Calculations (6 points each)

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.

12. The gas-phase reaction H + D2 → HD + D is the exchange of isotopes of hydrogen and deuterium. This occurs at 299 K with a measured rate constant of 1.56 x 104 /Ms and at 745 K with a measured rate constant of 1.0 x 107 /Ms. Calculate the activation energy (in kJ) for this reaction.

a. 0.27 b. 2.3 c. 27 d. 990 e. 1200 13. The rate constant for a first-order reaction is k = 0.00073/s. Determine the percent of reactant that has decomposed after 500 s.

a. 69% b. 57% c. 37% d. 31% e. 43% 14. In the reaction C4H9Cl(aq) + H2O(l) → C4H9OH(aq) + HCl(aq) the concentration of the reactant changes from 0.0562 M to 0.0431 M in 85 sec. What is the average rate of decomposition over this interval?

a. 1.54 × 10-4 M/s b. 1.54 × 10-4 moles c. 1.54 × 10-4 moles/s d. 0.0154 M e. 0.0154 M/s

15. The half-life of U-238, which decomposes to Pb-206, is 4.51 × 109 y. A rock contains equal masses of these two isotopes. How old is this rock?

a. 4.07 × 109 y b. 4.06 × 109 y c. 9.02 × 109 y d. 4.51 × 109 y e. 5.00 × 109 y

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Part II: Short Calculations, Fill in the Blank

16. (3 points total) Fill in the blank: in the column marked “Answer” to the left of each statement, fill in the box with the spectroscopy that best describes the statement.

Answer Statement – Which element is it?

NMR 1. An MRI is a medicinal application of this spectroscopy.

IR

2. This spectroscopy is used to observe vibrational states of a molecule.

UV/Vis 3. Using this spectroscopy, light is introduced into a sample which excites

electrons from a π to a π* energy state. 17. (8 points total) Answer each question with respect to the given molecule.

How many sp3 hybridized atoms are present? 5

How many H atoms are present? 11

How many π bonds are present? 3 How many σ bonds are present? 23

18. (9 points total) Circle the most stable nuclide in each of the following lists.

a. O-16 Uuq-298 Mn-50 Br-82 F-20

b. V-50 H-3 Ca-48 B-11 Cf-251 c. Pb-208 Bi-209 Tl-205 Na-24

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19. (6 points total)

a. (4 points) Identify the following molecules as chiral or achiral. Designate the molecule as cis, trans, R, S, or none.

b. (2 points) Draw R-2-chloropentane

20. (14 points total) In each box, label the functional group of each molecule. Label any chiral centers with an asterisk (*).

Organic (or Alkyl) Halide

Alkene Ester

Amide Aldehyde Alcohol

Molecule Chiral (optically active) or Achiral (optically inactive)? Designation

Chiral R

Achiral Cis or Z

* *

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21. (18 points total; 3 points each) Draw the structure to represent the principal (major) product of each of the following reactions. If no reaction occurs, write N.R. Parts c, d, e, and f must be balanced for credit.

a. + HBr →

b. + Br2 (with hν) →

c. C-13 + p → γ + N-14

d. F-19 + α → p + Ne-22

e. p + H-3 → He-4

f. Po-214 + 2 α + 2 β- → Rn-222

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22. (2 points) Write the name of the organic molecule in the space provided.

Name: 2,5-dibromo-3-ethyl-4-isopropyl-6-methyloctane______ 23. (9 points total) The rate for the oxidation of iron(II) by cerium(IV):

Ce4+(aq) + Fe2+(aq) → Ce3+(aq) + Fe3+(aq) Is measured at different initial concentrations of the reactants:

Trial [Ce4+]o (x 10-5) [Fe2+]o (x 10-5) Initial Rate (x 10-7) 1 1.1 M 1.8 M 2.0 Ms-1 2 1.1 M 2.8 M 3.1 Ms-1 3 3.4 M 2.8 M 9.5 Ms-1

a. What is the order of reaction with respect to Ce4+ and Fe2+? Rate Law: Rate = k [Ce4+]x [Fe2+]y

a. x = 1; y = 1 b. x = 1; y = 0 c. x = 0; y = 1 d. x = 2; y = 2 e. x = 0; y = 0

b. What are the units of k (rate constant) in this question?

a. M/s b. 1/(Ms) c. unitless d. 1/s e. M

c. Predict the initial reaction rate (in M/s) for a solution in which [Ce4+] is 2.6 x10-5 M and [Fe2+] is 1.3 x 10-5 M.

a. 0.998 b. 998 c. 3.4 x 10-7 d. 3.4 x 10-10 e. None of these

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

24. (14 points total) A proposed mechanism for the decomposition of acetaldehyde is

Step 1: CH3CHO → CH3· + CHO·

Step 2: CH3· + CH3CHO → CH4 + CO + CH3·

Step 3: CHO· + CH3CHO → CH3· + 2 CO + H2

Step 4: 2 CH3· → C2H6

a. (2 points) List all the intermediates of the proposed mechanism. CH3·, CHO·

b. (2 points) Write the rate for Step 2. r2 = k2 [CH3·][CH3CHO]

c. (10 points) Assuming that CH3·and CH3CO· are in a steady state, derive an expression for the rate of formation of CH4 in terms of acetaldehyde (CH3CHO) concentration. Note: All reactions given above are forward reactions only. Hint: Use PSSH on both intermediates. Circle your answer!

Solve for r2 = k2 [CH3·][CH3CHO]

PSSH (CHO·): r1 = r3

PSSH (CH3·): r1 + r3 = 2 r4 or r1 + r3 = 2 r4 Thus, r1 = r3 = r4, so use 1 and 4 k1[CH3CHO] = k4[CH3·]2, so [CH3·] = (k1/k4)0.5[CH3CHO]0.5

Thus, r2 = k2(k1/k4)0.5[CH3CHO]1.5

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25. (13 points total) Complete the isomer problem below. Each correctly drawn isomer is 1 point. For each duplicate or incorrect isomer, you will lose 1 point. You cannot score below a zero on this problem.

a. (1 point) What is the degree of unsaturation of C3H6O? 1 b. (8 points) Draw all the structural isomers for C3H6O.

c. (2 points) Draw all the geometric isomers for C3H6O, if any. Label cis or trans.

Trans & Cis

d. (2 points) Draw all the optical isomers for C3H6O, if any. Label R or S.

S & R

e. (1 point EC) How many total isomers (structural, geometric, optical) could be drawn? 11

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26. (10 points total) Carbon-11 decays by positron emission to boron-11. The atomic mass of carbon-11 is 11.01143 u and that for boron-11 is 11.00931.

a. (4 points) Write the nuclear reaction.

𝑪𝟔𝟏𝟏 → 𝑩 + 𝜷!𝟏𝟎

𝟓𝟏𝟏

b. (3 points) Find the energy (J/nuclei) released by this nuclear reaction.

Δm = (11.00931 + 0.00054848) – 11.01143 = -0.001572 u

-0.001572 u (1.4924e-10 J / 1 u) = 2.346e-13 J/nuclei

c. (3 points) Assuming that the energy associated with the reaction ends up as kinetic energy of the positron, calculate its velocity.

eK = ½ mu2 = 2.346e-13 J/nuclei = ½(0.00054848 u)( u2)(1.6605 x 10-27 kg / u)

u = 7.178e8 m/s

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Name Final (Page 13 of 13)

Constants: R = 8.3145 J / mol K NA = 6.022 x 1023 c = 2.9979 x 108 m/s 1 MeV = 1.6 x 10-13 J R = 0.0821 L atm / mol K h = 6.626 x 10-34 J s 1 nm = 10-9 m 1 mL = 1 cm3 F = 96,485 C/ mol e- 1 u = 1.6605 x 10-27 kg 1 g = 6.02 x 1023 u 931.5 MeV = 1 u Neutron mass = 1.00867 u Proton mass = 1.00783 u 1 u = 1.4924e-10 J Electron mass = 0.00054848 u 1 Ci = 1 Curie = 3.7e10 disintegrations/s = 3.7e10 Bq = 3.7e10 Becquerel Equations:

nRTPV = ⎟⎟⎠

⎞⎜⎜⎝

⎛−=

122

1 11lnTTR

Ekk α νh=Δ λν=c ΔE = Δmc2 RT

Ea

eAk−

= eK = ½ mu2

kAkrate == 0][ 0][][ AktA t +−= kAt2][ 0

21 =

ktAktAAkrate t

693.0]ln[]ln[][210 =+−==

00

2

][1

][1

][1][

21 Akt

Akt

AAkrate

t

=+==

Rate of decay = λ N where N = # of remaining atoms ln Nt = ln No – λt Magic numbers for protons: 2, 8, 20, 28, 50, 82, 114 Magic numbers for neutrons: 2, 8, 20, 28, 50, 82, 126, 184