CHEMISTRY 2A Exam II
Name_____________________________________ _ Student ID Number_________________________
__
Lab TA Name and Time___________________ ______ Fall 2012 – Enderle
CHEMISTRY 2A Exam II 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. (1) Read each question carefully. Circle Part I answers on front page. (2) There is no partial credit for the problems in Part I. You will lose 10 points if you do not circle your multiple choice answers on the front page or if you do not write your TA’s name in the space above. (3) The last two pages contain a periodic table and some useful information. You may remove these pages for easy access. (4) Graded exams will be returned in lab sections next week. (5) If you finish early, RECHECK YOUR ANSWERS!
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
13.
A
B
C
D E
19. 19 points
14.
A
B
C
D E
20. 14 points
15.
A
B
C
D E
U.C. Davis is an Honor Institution Possible Points 1–15. 45 points 16–17. 14 points 18. 15 points
Total Score (107)
Points
Exam II
Page 2 of 10
Part I: Multiple Choice, Concepts & Short Calculations Circle the correct answer and enter your response on the cover – No partial credit 1. Which of the following would generally not apply to quantum mechanics? A. There is a discrete or discontinuous nature to energy B. Blackbody radiation is one concept that reinforces quantum mechanics C. Only certain energies are allowable D. Quantum mechanics overruled classical mechanics, which is now obsolete and invalid 2. Simplify the units of the following: N A. N B. J C. m / s D. Pa
E. m
3. Which of the following is not an assumption in the kinetic theory of gases? A. Gases occupy an infinitesimally small volume. B. Gases travel in rapid, straight lines. C. When gases collide, they collide in a fully elastic collision with no loss in energy D. Kinetic energy is proportional to volume E. There is no attraction between gas molecules 4. At STP, CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (l). If 20.0 L of O2 react with 5.0 L of CH4, how much CO2 (g) is formed? A. 0.22 L B. 10.0 L C. 5.0 L D. 20.0 L 5. What color light corresponds to the transition of an electron from n = 3 to n = 2 in a Bohr hydrogen atom? A. violet B. blue C. green D. red E. polkadot 6. A 5.00 mL sample of a nitric acid solution is titrated with 33.5 mL of 0.201 M NaOH. What is the molarity of the nitric acid solution? A. 0.0300 M B. 0.149 M C. 1.35 M D. 6.7 M 7. What pressure must be applied to N2 (g) to obtain a density of 2.00 g/L at 25°C? A. 1.75 atm B. 0.146 atm C. 111 atm D. 3.49 atm 8. To increase the volume of a fixed amount of gas from 100 cm3 to 200 cm3: A. increase the temperature from 25.0 to 50.0°C at constant pressure B. increase the pressure from 1.00 to 2.00 atm at constant temperature C. reduce the temperature from 400 K to 200 K at constant pressure D. reduce the pressure from 608 mmHg to 304 mmHg at constant temperature E. decrease the temperature from 600 K to 400 K 9. What is the wavelength of a ball that is 25.0 g traveling at 40.2 m/s? A. 6.59 × 10-37 m B. 6.59 × 10-34 m C. 1.07 × 10-30 m D. 4.12 × 10-37 m
Exam II
Page 3 of 10
10. Which of the following is the weakest acid? A. HF B. HCl C. HBr D. HI 11. Which of the following is the correct net ionic equation when KHCO3 (aq) is mixed in solution with HCl (aq)? A. KHCO3 (aq) + HCl (aq) H2CO3 (aq) + KCl (aq) B. HCO3- (aq) + H+ (aq) H2CO3 (aq) C. KHCO3 (aq) + HCl (aq) K2CO3 (aq) + 2 HCl (aq) D. HCO3- (aq) + H+ (aq) H2O (l) + CO2 (g) 12. Which of the following likely indicates a reduction half reaction? A. There are more O atoms in the final product B. There is an increase in oxidation state C. There are less H atoms in the final product D. There are electrons in the reactants E. Electrons are lost 13. Which of the following are effectively insoluble in water? A. Pb(ClO3)2 B. (NH4)3PO4 C. HgSO4 D. AgBr E. NaCl 14. Which one of the following reactants will definitely produce this net ionic equation when mixed in solution? H+ (aq) + OH- (aq) H2O (l) A. acetic acid and ammonia B. hydrochloric acid and ammonia C. acetic acid and potassium hydroxide D. hydrochloric acid and potassium hydroxide 15. What is the uncertainty of the position (in m) of a 0.40 kg football thrown at 40 m/s, where the velocity is know at a precision of 0.0001%? A. 3 x 1029 B. 3 x 10-30 C. 1 x 10-29 D. 3 x 10-36
Exam II
Page 4 of 10
Part II: Short Answer 16. (6 points) Fill in the blanks with the correct ground state electron configuration (noble gas configuration in spdf condensed form). Think carefully about the second and third part. Atom
Electron Configuration
F
1s2 2s2 2p5 OR [He] 2s2 2p5
Tl
[Xe] 6s2 4f14 5d10 6p1 OR 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p1
Am
[Rn] 7s2 6d1 5f 6
17. (8 points) Given 238UF6 and 235UF6 at 300 K, fill in all your answers in the table below. When answers are numerical, use three significant figures. Ratio of effusion rates of 238
UF6 to 235UF6
Which compound travels faster?
0.996 235
UF6
Root mean square velocity of 235UF6 (in m/s)
146
Kinetic energy of the sample (in Joules)
3740
Exam II
Page 5 of 10
Part III: Long Answer Please show all work – Partial credit 18. (15 total points) Given the following equation: Al2O (s) + O2 (g) [Al(OH)4]- (aq) A. (2 points) What is reduced? What is the reducing agent? Reduced:
O or O2
Reducing Agent: Al or Al2O
B. (1 point) What is the intermediate? Electrons or eC. (3 points) Balance the reduction half reaction (acidic solution). O2 (g) + 4 H+ (aq) + 4 e- 2 H2O (l)
D. (3 points) Balance the oxidation half reaction (acidic solution). Al2O (s) + 7 H2O (l) 2 [Al(OH)4]- (aq) + 6 H+ (aq) + 4 e-
E. (6 points) Give the overall reaction below (basic solution). No multipliers needed to add because there are 4 electrons on each side Al2O (s) + 5 H2O (l) + O2 (g) 2 [Al(OH)4]- (aq) + 2 H+ (aq) Add 2 OH- (aq) to each side and simplify. Al2O (s) + 5 H2O (l) + O2 (g) 2 [Al(OH)4]- (aq) + 2 H+ (aq) Al2O (s) + 3 H2O (l) + O2 (g) + 2 OH- (aq) 2 [Al(OH)4]- (aq)
Exam II
Page 6 of 10
19. (19 pts) Quantum number questions:
Answers:
For a 3p orbital, what is the value of n and ℓ?
3, 1
Which of the following orbitals are not allowed: (3) 5f, ms = -½ or (2) 3d, mℓ = 3?
(2)
Which of the following orbitals has the most nodes: 5s, 4p, 3d, or 4f?
5s
What is the lowest energy p orbital?
2p
A 4p orbital has how many values of mℓ?
3
For ℓ = 3, how many orbitals are expected?
7
How many electrons can have n = 4 and ms = –½?
16
How many internal nodes are seen in the particle in a box graph below? What is n?
5, 6
0
L
Draw a 3pz orbital. Remember to label the axis and all nodes, if any.
Answer: 3pz Orbital (p orbital on the z axis with 2 nodes)
Exam II
Page 7 of 10
20. (14 points) A 1.37 L vessel contains He at a temperature of 24.5°C and a pressure of 205 mmHg. A 721 mL vessel contains Ne at a temperature of 36.2°C and a pressure of 0.185 atm. Both of these gases are placed in a 2.00 L vessel at 302 K. A. Find the moles of He and Ne before these gases are mixed. 205 1.37 760 0.08206 24.5 273
PV RT
n n
0.185 0.721 0.08206 36.2 273
. .
B. Find the mole fraction of He and Ne after these gases are mixed. n
0.0151 x x
0.00525 0.0151 0.02035 0.00525 0.02035
0.02035 mol . .
C. Find the total pressure (in atm) after these gases are mixed. P
n
RT V
0.02035 0.08206 302 2
.
D. Find the partial pressure of He and Ne (in atm) after these gases are mixed. P P
x P x P
0.742 0.252 0.258 0.252
. .
Exam II SCRATCH PAPER:
Page 8 of 10
Exam II
Page 9 of 10
Solubility Rules: Compounds that are soluble or mostly soluble • Group 1, NH4+, chlorates, acetates, nitrates • Halides (except Pb2+, Ag+, and Hg22+) • Sulfates (except Ca2+, Sr2+, Ba2+, Pb2+, and Hg22+) Compounds that are insoluble • Hydroxides, sulfides (except above rule, and group 2 sulfides) • Carbonates, phosphates, chromates (except above rules) Conversions: 1 atm = 14.7 psi = 101,325 Pa = 760 mmHg = 1.01325 bar = 760 Torr; 1in = 2.54 cm; 12 in = 1 ft Constants: R = 8.3145 J / mol K = 0.08206 L atm / mol K c = 2.9979 x 108 m / s h = 6.626 x 10-34 J s 2 g = 9.81 m / s m (electron) = 9.109 x 10-31 kg 3 d (H2O) = 1.0 g / cm
Avogadro’s number = 6.022 x 1023 / mol RH = 2.179 x 10-18 J m (proton) = 1.673 x 10-27 kg
Equations and Various Tables:
ax2 + bx + c = 0; x =
1 1 2 2 n 2
3.2881 1015 s 1
xp
h 4
b b 2 4ac 2a En
effusion rateA MB effusion rateB MA
Z 2 RH n2 Ek
n2h2 8mL2
h mu
P=dgh
E=hν
1 1 E RH 2 2 n i nf
c=λν eK = ½mu2 = 3/2RT
n2a P 2 V nb nRT V ( x)
2 nx sin , n 1,2,3,... L L
u rms u 2
PV = nRT
3RT M Ptotal = P1 + P2 + …
xA = nA / ntot = PA / Ptot = VA / Vtot
Exam II
Page 10 of 10
__
Lab TA Name and Time___________________ ______ Fall 2012 – Enderle
CHEMISTRY 2A Exam II 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. (1) Read each question carefully. Circle Part I answers on front page. (2) There is no partial credit for the problems in Part I. You will lose 10 points if you do not circle your multiple choice answers on the front page or if you do not write your TA’s name in the space above. (3) The last two pages contain a periodic table and some useful information. You may remove these pages for easy access. (4) Graded exams will be returned in lab sections next week. (5) If you finish early, RECHECK YOUR ANSWERS!
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
13.
A
B
C
D E
19. 19 points
14.
A
B
C
D E
20. 14 points
15.
A
B
C
D E
U.C. Davis is an Honor Institution Possible Points 1–15. 45 points 16–17. 14 points 18. 15 points
Total Score (107)
Points
Exam II
Page 2 of 10
Part I: Multiple Choice, Concepts & Short Calculations Circle the correct answer and enter your response on the cover – No partial credit 1. Which of the following would generally not apply to quantum mechanics? A. There is a discrete or discontinuous nature to energy B. Blackbody radiation is one concept that reinforces quantum mechanics C. Only certain energies are allowable D. Quantum mechanics overruled classical mechanics, which is now obsolete and invalid 2. Simplify the units of the following: N A. N B. J C. m / s D. Pa
E. m
3. Which of the following is not an assumption in the kinetic theory of gases? A. Gases occupy an infinitesimally small volume. B. Gases travel in rapid, straight lines. C. When gases collide, they collide in a fully elastic collision with no loss in energy D. Kinetic energy is proportional to volume E. There is no attraction between gas molecules 4. At STP, CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (l). If 20.0 L of O2 react with 5.0 L of CH4, how much CO2 (g) is formed? A. 0.22 L B. 10.0 L C. 5.0 L D. 20.0 L 5. What color light corresponds to the transition of an electron from n = 3 to n = 2 in a Bohr hydrogen atom? A. violet B. blue C. green D. red E. polkadot 6. A 5.00 mL sample of a nitric acid solution is titrated with 33.5 mL of 0.201 M NaOH. What is the molarity of the nitric acid solution? A. 0.0300 M B. 0.149 M C. 1.35 M D. 6.7 M 7. What pressure must be applied to N2 (g) to obtain a density of 2.00 g/L at 25°C? A. 1.75 atm B. 0.146 atm C. 111 atm D. 3.49 atm 8. To increase the volume of a fixed amount of gas from 100 cm3 to 200 cm3: A. increase the temperature from 25.0 to 50.0°C at constant pressure B. increase the pressure from 1.00 to 2.00 atm at constant temperature C. reduce the temperature from 400 K to 200 K at constant pressure D. reduce the pressure from 608 mmHg to 304 mmHg at constant temperature E. decrease the temperature from 600 K to 400 K 9. What is the wavelength of a ball that is 25.0 g traveling at 40.2 m/s? A. 6.59 × 10-37 m B. 6.59 × 10-34 m C. 1.07 × 10-30 m D. 4.12 × 10-37 m
Exam II
Page 3 of 10
10. Which of the following is the weakest acid? A. HF B. HCl C. HBr D. HI 11. Which of the following is the correct net ionic equation when KHCO3 (aq) is mixed in solution with HCl (aq)? A. KHCO3 (aq) + HCl (aq) H2CO3 (aq) + KCl (aq) B. HCO3- (aq) + H+ (aq) H2CO3 (aq) C. KHCO3 (aq) + HCl (aq) K2CO3 (aq) + 2 HCl (aq) D. HCO3- (aq) + H+ (aq) H2O (l) + CO2 (g) 12. Which of the following likely indicates a reduction half reaction? A. There are more O atoms in the final product B. There is an increase in oxidation state C. There are less H atoms in the final product D. There are electrons in the reactants E. Electrons are lost 13. Which of the following are effectively insoluble in water? A. Pb(ClO3)2 B. (NH4)3PO4 C. HgSO4 D. AgBr E. NaCl 14. Which one of the following reactants will definitely produce this net ionic equation when mixed in solution? H+ (aq) + OH- (aq) H2O (l) A. acetic acid and ammonia B. hydrochloric acid and ammonia C. acetic acid and potassium hydroxide D. hydrochloric acid and potassium hydroxide 15. What is the uncertainty of the position (in m) of a 0.40 kg football thrown at 40 m/s, where the velocity is know at a precision of 0.0001%? A. 3 x 1029 B. 3 x 10-30 C. 1 x 10-29 D. 3 x 10-36
Exam II
Page 4 of 10
Part II: Short Answer 16. (6 points) Fill in the blanks with the correct ground state electron configuration (noble gas configuration in spdf condensed form). Think carefully about the second and third part. Atom
Electron Configuration
F
1s2 2s2 2p5 OR [He] 2s2 2p5
Tl
[Xe] 6s2 4f14 5d10 6p1 OR 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p1
Am
[Rn] 7s2 6d1 5f 6
17. (8 points) Given 238UF6 and 235UF6 at 300 K, fill in all your answers in the table below. When answers are numerical, use three significant figures. Ratio of effusion rates of 238
UF6 to 235UF6
Which compound travels faster?
0.996 235
UF6
Root mean square velocity of 235UF6 (in m/s)
146
Kinetic energy of the sample (in Joules)
3740
Exam II
Page 5 of 10
Part III: Long Answer Please show all work – Partial credit 18. (15 total points) Given the following equation: Al2O (s) + O2 (g) [Al(OH)4]- (aq) A. (2 points) What is reduced? What is the reducing agent? Reduced:
O or O2
Reducing Agent: Al or Al2O
B. (1 point) What is the intermediate? Electrons or eC. (3 points) Balance the reduction half reaction (acidic solution). O2 (g) + 4 H+ (aq) + 4 e- 2 H2O (l)
D. (3 points) Balance the oxidation half reaction (acidic solution). Al2O (s) + 7 H2O (l) 2 [Al(OH)4]- (aq) + 6 H+ (aq) + 4 e-
E. (6 points) Give the overall reaction below (basic solution). No multipliers needed to add because there are 4 electrons on each side Al2O (s) + 5 H2O (l) + O2 (g) 2 [Al(OH)4]- (aq) + 2 H+ (aq) Add 2 OH- (aq) to each side and simplify. Al2O (s) + 5 H2O (l) + O2 (g) 2 [Al(OH)4]- (aq) + 2 H+ (aq) Al2O (s) + 3 H2O (l) + O2 (g) + 2 OH- (aq) 2 [Al(OH)4]- (aq)
Exam II
Page 6 of 10
19. (19 pts) Quantum number questions:
Answers:
For a 3p orbital, what is the value of n and ℓ?
3, 1
Which of the following orbitals are not allowed: (3) 5f, ms = -½ or (2) 3d, mℓ = 3?
(2)
Which of the following orbitals has the most nodes: 5s, 4p, 3d, or 4f?
5s
What is the lowest energy p orbital?
2p
A 4p orbital has how many values of mℓ?
3
For ℓ = 3, how many orbitals are expected?
7
How many electrons can have n = 4 and ms = –½?
16
How many internal nodes are seen in the particle in a box graph below? What is n?
5, 6
0
L
Draw a 3pz orbital. Remember to label the axis and all nodes, if any.
Answer: 3pz Orbital (p orbital on the z axis with 2 nodes)
Exam II
Page 7 of 10
20. (14 points) A 1.37 L vessel contains He at a temperature of 24.5°C and a pressure of 205 mmHg. A 721 mL vessel contains Ne at a temperature of 36.2°C and a pressure of 0.185 atm. Both of these gases are placed in a 2.00 L vessel at 302 K. A. Find the moles of He and Ne before these gases are mixed. 205 1.37 760 0.08206 24.5 273
PV RT
n n
0.185 0.721 0.08206 36.2 273
. .
B. Find the mole fraction of He and Ne after these gases are mixed. n
0.0151 x x
0.00525 0.0151 0.02035 0.00525 0.02035
0.02035 mol . .
C. Find the total pressure (in atm) after these gases are mixed. P
n
RT V
0.02035 0.08206 302 2
.
D. Find the partial pressure of He and Ne (in atm) after these gases are mixed. P P
x P x P
0.742 0.252 0.258 0.252
. .
Exam II SCRATCH PAPER:
Page 8 of 10
Exam II
Page 9 of 10
Solubility Rules: Compounds that are soluble or mostly soluble • Group 1, NH4+, chlorates, acetates, nitrates • Halides (except Pb2+, Ag+, and Hg22+) • Sulfates (except Ca2+, Sr2+, Ba2+, Pb2+, and Hg22+) Compounds that are insoluble • Hydroxides, sulfides (except above rule, and group 2 sulfides) • Carbonates, phosphates, chromates (except above rules) Conversions: 1 atm = 14.7 psi = 101,325 Pa = 760 mmHg = 1.01325 bar = 760 Torr; 1in = 2.54 cm; 12 in = 1 ft Constants: R = 8.3145 J / mol K = 0.08206 L atm / mol K c = 2.9979 x 108 m / s h = 6.626 x 10-34 J s 2 g = 9.81 m / s m (electron) = 9.109 x 10-31 kg 3 d (H2O) = 1.0 g / cm
Avogadro’s number = 6.022 x 1023 / mol RH = 2.179 x 10-18 J m (proton) = 1.673 x 10-27 kg
Equations and Various Tables:
ax2 + bx + c = 0; x =
1 1 2 2 n 2
3.2881 1015 s 1
xp
h 4
b b 2 4ac 2a En
effusion rateA MB effusion rateB MA
Z 2 RH n2 Ek
n2h2 8mL2
h mu
P=dgh
E=hν
1 1 E RH 2 2 n i nf
c=λν eK = ½mu2 = 3/2RT
n2a P 2 V nb nRT V ( x)
2 nx sin , n 1,2,3,... L L
u rms u 2
PV = nRT
3RT M Ptotal = P1 + P2 + …
xA = nA / ntot = PA / Ptot = VA / Vtot
Exam II
Page 10 of 10
