Chemistry 222 Winter 2012 Oregon State University

Exam 2 March 1, 2012 Drs. Nafshun, Ferguson, and Watson

Instructions: You should have with you several number two pencils, an eraser, your 3" x 5" note

card, a calculator, and your University ID Card. If you have notes with you, place them in a

sealed backpack and place the backpack OUT OF SIGHT or place the notes directly on the table

at the front of the room.

Fill in the front page of the Scantron answer sheet with your class section number (see below),

last name, first name, middle initial, and student identification number. Leave the test form

number blank.

Section 001 (MWF 8am with Dr. Nafshun) Section 002 (MWF 11am with Dr. Watson)

Section 003 (MWF 1pm with Dr. Ferguson) Section 004 (MWF 3pm with Dr. Ferguson)

Section 006 (TR 8am with Dr. Nafshun)

This exam consists of 22 multiple-choice questions; each has 5 points attached. The last

question (Question 23) has 2 points attached. When you finish this exam, proceed to the proctor.

Submit your completed Scantron form. You may take your notecard and exam packet with you.

Zero-Order First-Order Second-Order

t1=[A]0/2k t1/2=ln2/k=0.693/k t1/2=1/k[A]0

R = 0.08206 L•atm/mol•K = 8.314 J/mol•K 760 mm Hg = 760 torr = 1 atm NA = 6.022 x 10

23

1 m = 1 x 1012

pm 1 m = 100 cm

Abbreviated Solubility Rules:

Rule 1: All nitrates, group 1A metal salts and ammonium salts are soluble.

Rule 2: All carbonates, hydroxides, phosphates and sulfides are insoluble.

Rule 3: I-, Cl

-, Br

- are soluble except when combined with Ag

+ Pb

2+ Hg2

2+

Rule 4: Rule 1 always takes precedent.

1. Sodium chloride melts at 804 ºC. Sodium iodide melts at 651 ºC. The difference in

melting points can be mainly attributed to:

(A) The larger iodide ion has larger dispersion forces.

(B) The iodide ion has a larger charge than the chloride ion.

(C) The distance between the nuclei in NaCl is shorter.

(D) NaCl has lower Coulombic forces.

(E) One is a molecule (attractions by intermolecular forces), one is an ionic

compound (attractions by charges; Coulomb's Law)

2. Consider CH3CH2OH (ethanol) and CH3OCH3 (dimethyl ether). Which of the following

statements is false?

(A) Both compounds exhibit dispersion forces.

(B) Both compounds exhibit intermolecular forces of equivalent strength.

(C) Only dimethyl ether does not exhibit hydrogen bonding.

(D) Both are molecular compounds.

(E) Ethanol has a higher boiling point than dimethyl ether.

3. Consider the generic phase diagram below. Which answer best describes the sequence of

events on starting at point A and going to point D?

A) A is liquid; at B the liquid freezes at its normal freezing point; C is solid and D is gas.

B) A is solid; at B the solid sublimes to the gas; C is gas and D is liquid.

C) A is gas; at B the gas condenses at its boiling point; C is liquid and D is solid.

D) A is solid; at B the solid melts at its normal melting point; C is liquid and D is gas.

E) A is liquid; at B the liquid boils at its normal boiling point; C is gas and D is solid.

4. A metal crystallizes in a face centered cubic structure and has a density of 12.02 g/cm3.

If the radius of the metal atom is 137 pm, what is the identity of the metal?

A) At

B) Pd

C) Mn

D) Fe

E) Cr

Pressure

1 atm

Temperature

1 atm

C

A B

D

5. Which of the following is FALSE?

(A) The FCC structure unit cell contains four equivalent atoms.

(B) The length of a side of a BCC unit cell is 4r/√3.

(C) The center atom in a BCC unit cell is completely contained in the unit cell.

(D) The SC structure unit cell contains two equivalent atoms.

(E) The SC structure consists of approximately 1/2 matter and 1/2 empty space.

6. Consider the plot below. Which of the following is FALSE?

(A) Curve “A” has the highest vapor pressure of all the curves shown

(B) Curve "E" corresponds to a compound with stronger intermolecular forces than curve “C"

(C) The compound corresponding to curve "B" is a gas at 20ºC and 200 mm Hg

(D) The vapor pressure of the compound corresponding to curve "E" at 140ºC is 200 mm Hg

(E) The normal boiling point of the compound corresponding to curve "B" is 80ºC

7. How much heat is required to warm 3.000 kg of benzene from 0°C to 10°C?

(A) 57.00 kJ

(B) 126 kJ

(C) 397.5 kJ

(D) 35.59 kJ

(E) 413.6 kJ

8. A student takes 400 mL of a 2.00 M aqueous solution of (NH4)2S and adds 200 mL of

water. What is the concentration of NH4+ ions in the resulting solution?

(A) 2.66 M

(B) 2.00 M

(C) 1.33 M

(D) 1.50 M

(E) 0.750 M

9. Give the net ionic equation for the reaction (if any) that occurs when aqueous solutions

of K2S and Pb(NO3)2 are mixed.

(A) K+(aq) + NO3

-(aq) → KNO3(s)

(B) Pb2+

(aq) + S2-

(aq) + 2 K+(aq) + 2 NO3

-(aq) → PbS(s) + 2 K

+(aq) + 2 NO3

-(aq)

(C) Pb2+

(aq) + S2-

(aq) + 2 K+(aq) + 2 NO3

-(aq) → Pb

2+(aq) + S

2-(aq) + 2 KNO3(s)

(D) Pb2+

(aq) + S2-

(aq) → PbS(s)

(E) No reaction occurs

10. A student dissolves 12.000 g of an unknown polymer in 800 mL of water at 320 K. She

measures the osmotic pressure to be 0.0677 mm Hg. What is the molar mass of the

polymer?

(A) 2.71 x 106 g/mol

(B) 4.42 x 106 g/mol

(C) 1.73 x 105 g/mol

(D) 1.73 x 106 g/mol

(E) 2.26 x 106 g/mol

11. The freezing point of 0.125 moles Na2CO3 dissolved in 250 grams of water is:

(A) -2.79 C

(B) +2.79 C

(C) +5.58 C

(D) -5.58 C

(E) -0.93C

12. Sulfuric acid is 98% by mass H2SO4 in water. Determine the molality of the H2SO4 if the

solution has a density of 1.84 g/mL.

(A) 18.0m

(B) 500m

(C) 0.500m

(D) 0.0543m

(E) 0.999m

13. Which of the following statements is generally TRUE?

(A) The solubility of a solid is not dependent on either temperature or pressure.

(B) The solubility of a solid is highly dependent on pressure.

(C) The solubility of a solid is highly dependent on both pressure and temperature.

(D) The solubility of a solid is highly dependent on temperature.

(E) None of the above.

14. The following are initial rate data for: A + B C

Experiment Initial [A] Initial [B] Initial Rate (M/s)

1 0.10 0.10 5.1

2 0.20 0.10 10.2

3 0.10 0.25 80.

(A) The rate law is Rate = k[A]1[B]

2

(B) The rate law is Rate = k[A]0[B]

1

(C) The rate law is Rate = k[A]3[B]

0

(D) The rate law is Rate = k[A]1[B]

3

(E) The rate law is Rate = k[A]2[B]

3

15. The two diagrams below represents two sets of initial conditions for the second-order

reaction of oxygen atoms with nitrogen dioxide (one of the reactions involved in ozone

depletion from burning fuels) in a container with a fixed volume.

O(g) + NO2(g) → O2(g) + NO(g)

At the same temperature, what will be the relative initial rates of reaction in the two

cases?

(A) Rate (b) = Rate (a)

(B) Rate (b) = 1.50 Rate (a)

(C) Rate (b) = 2.00 Rate (a)

(D) Rate (b) = 2.25 Rate (a)

(E) Rate (b) = 0.444 Rate (a)

16. Which graph could correctly depict the changes in concentrations for the (note: in the

diagram, N2 and H2O share the same line).

Reaction: 2 N2 (g) + 5 O2 (g) + 2 H2O (l) → 4 HNO3 (aq)?

17. How many half-lives are required for the concentration of a reactant to decrease to 25%

of its original value?

(A) 1

(B) 3

(C) 1.5

(D) 2.5

(E) 2

18. The rate constant at a certain temperature for the first-order decomposition of N2O is

3.40 s-1. If we start with [N2O] = 2.50 M, what is the concentration after 0.500 seconds?

(A) 11.47 M

(B) 0.457 M

(C) 0.235 M

(D) 1.47 M

(E) .8M

19. The half-life for the second-order decomposition of HI is 15.4 s when the initial

concentration of HI is 0.67 M. What is the rate constant for this reaction?

(A) 1.0 × 10-2 M-1s-1

(B) 4.5 × 10-2 M-1s-1

(C) 9.7 × 10-2 M-1s-1

(D) 2.2 × 10-2 M-1s-1

(E) 3.8 × 10-2 M-1s-1

20. The first-order rearrangement of CH3NC is measured to have a rate constant of

3.61 x 10-15 s-1 at 298 K and a rate constant of 8.66 × 10-7 s-1 at 425 K. Determine the

activation energy for this reaction.

(A) 160 kJ/mol

(B) 240 kJ/mol

(C) 417 kJ/mol

(D) 127 kJ/mol

(E) 338 kJ/mol

21. Which of the following statements is False?

(A) Increasing the temperature of a reaction will increase the rate.

(B) Increasing the number of collisions will increase the rate of reaction.

(C) Lowering the activation energy will increase the rate of reaction.

(D) The addition of a catalyst will decrease the rate of a process.

(E) The addition of a catalyst will lower the activation energy of a process.

22. The rate law for the overall reaction can be determined for the following reaction

mechanism from:

2 NO2 (g) → NO3 (g) + NO (g) (slow)

NO3 (g) + CO (g) → NO2 (g) + CO2 (g) (fast)

(A) The slowest step

(B) The fastest step

(C) The combination of the steps

(D) Always the first step

(E) Always the last step

23. The Chemistry 222 Final Exam is Monday, March 19, 2012 at 8:00pm; yes, this is better

than early in the morning. After the chemistry final I will be...

(A) catching up on with the Kardashian's tweets

(B) covering my ceiling with Period Table entries

(C) be involved in some serious merrymaking

(D) preparing for my other seven final exams

(E) getting a head start on the CH 223 Mastering Chemistry assignments

[Any response will receive full credit; even no response]