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Midterm 2 Solved - General Chemistry - Fall 2013 | CHEM 162, Exams of Chemistry

University of Washington (UW) - SeattleChemistry
Prof. Frantisek Turecek

Material Type: Exam; Professor: Turecek; Class: GENERAL CHEMISTRY; Subject: Chemistry; University: University of Washington - Seattle; Term: Unknown 1989;

Typology: Exams

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Chem 162 Name: KEY
Midterm 2 Section:_____
DO NOT OPEN THIS TEST
UNTIL INSTRUCTED TO DO SO.
Chem 162A – Fall 2003 – Dr. Frank Turecek
AA QZ TH 10:30-11:20 MEB245 Margaret Gabriel
AB QZ TH 11:30-12:20 PAR313 Rachel Mohler
AC QZ TH 2:30-3:20 JHN119 Gordon Mitchell
AD QZ TH 1:30-2:20 KNE120 Margaret Gabriel
AE QZ TH 2:30-3:20 KNE220 Luke Adams
AF QZ TH 3:30-4:20 BAG260 Peter Hintze
AG QZ TH 10:30-11:20 BNS203 Rachel Mohler
AH QZ TH 11:30-12:20 PAA A212 Gordon Mitchell
AI QZ TH 12:30-1:20 LOW 116 Luke Adams
Instructions:
1. Write your name and section in the spaces provided above.
2. As you are taking the test, read the instructions for each section
carefully before answering the questions in that section.
3. Clearly indicate your answers. Unclear responses to multiple
choice or true / false questions will be graded as incorrect.
4. Stop taking the exam when you are instructed to do so. If you
continue to work after being told to stop, you exam will not be
accepted for grading.
5. If you finish your exam early, please leave quietly so as not to
disturb other students. Be especially careful to open and close the
doors to BAG 131 as quietly as possible.
Useful constants Your score
R = 8.31451 J mol-1 K-1 Part A: _____ / 45
R = 0.08206 L atm mol-1 K-1 Part B: _____ / 20
Kf for water = 1.86 C kg mol-1 Part C: _____ / 35
Na = 6.022(1023) atoms mol-1 ________________________
1 pm = 10-12 m Total: _____ / 100
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Download Midterm 2 Solved - General Chemistry - Fall 2013 | CHEM 162 and more Exams Chemistry in PDF only on Docsity!

Chem 162 Name: KEY

Midterm 2 Section:_____

DO NOT OPEN THIS TEST

UNTIL INSTRUCTED TO DO SO.

Chem 162A – Fall 2003 – Dr. Frank Turecek

AA QZ TH 10:30-11:20 MEB245 Margaret Gabriel AB QZ TH 11:30-12:20 PAR313 Rachel Mohler AC QZ TH 2:30-3:20 JHN119 Gordon Mitchell AD QZ TH 1:30-2:20 KNE120 Margaret Gabriel AE QZ TH 2:30-3:20 KNE220 Luke Adams AF QZ TH 3:30-4:20 BAG260 Peter Hintze AG QZ TH 10:30-11:20 BNS203 Rachel Mohler AH QZ TH 11:30-12:20 PAA A212 Gordon Mitchell AI QZ TH 12:30-1:20 LOW 116 Luke Adams

Instructions:

1. Write your name and section in the spaces provided above.

2. As you are taking the test, read the instructions for each section

carefully before answering the questions in that section.

3. Clearly indicate your answers. Unclear responses to multiple

choice or true / false questions will be graded as incorrect.

4. Stop taking the exam when you are instructed to do so. If you

continue to work after being told to stop, you exam will not be

accepted for grading.

5. If you finish your exam early, please leave quietly so as not to

disturb other students. Be especially careful to open and close the

doors to BAG 131 as quietly as possible.

Useful constants Your score

R = 8.31451 J mol

K

Part A: _____ / 45

R = 0.08206 L atm mol-1^ K-1^ Part B: _____ / 20

Kf for water = 1.86 C kg mol

Part C: _____ / 35

Na = 6.022(10^23 ) atoms mol-1^ ________________________

1 pm = 10-12^ m Total: _____ / 100

Part A: Multiple choice (3 pts each) Circle the correct answer. There is only one correct answer per question. Unclear responses will be graded as incorrect.

1. Which of the following compounds is a molecular solid at 298 K and 1 atm? a. Br 2 b. BaSO 4 c. Al 2 Cl 6 d. LiI e. SO 2 2. Which of the following compounds is a network solid? a. Fe b. GaAs c. I 2 d. NaCl e. SiO 2 3. The vapor pressure of liquid water is 17.5 torr at 20 C and 176 torr at 80 C. What is the enthalpy of vaporization of liquid water in kJ mol-1? a. 33.1 b. -33.1 c. -30.7 d. -5.1 e. 5. 4. The boiling points of Group 5A hydrides follow the series: a. NH 3 < PH 3 < AsH 3 < SbH 3 b. AsH 3 > SbH 3 > NH 3 > PH 3 c. SbH 3 > NH 3 > AsH 3 > PH 3 d. PH 3 > AsH 3 > NH 3 > SbH 3 e. NH 3 > SbH 3 > AsH 3 > PH 3 5. When the temperature of a liquid is increased the corresponding vapor pressure: a. always decreases b. always increases c. decreases only if Hvap < 0 d. increases only if Hvap < 0 e. does not change 6. The boiling points of 4 common hydrocarbons at 1 atm are as follows: Pentane Hexane Heptane Octane 36 ºC 69 ºC 98 ºC 126 ºC The corresponding vapor pressures at 25 ºC follow the series: a. pentane > hexane > heptane > octane b. pentane < hexane < heptane < octane c. pentane > hexane < heptane < octane d. pentane < hexane > heptane > octane e. pentane > hexane > heptane = octane

14. Which of the following compounds is used as a rocket fuel? a. NH 4 NO 3 b. H 2 S c. NH 4 ClO 4 d. NaOCl e. H 2 S 2 O 8 15. Hydrogenation is an important reaction using molecular hydrogen. Ethylene (C 2 H 4 ) can be hydrogenated to form ethane (C 2 H 6 ) in the following manner: C 2 H4(g) + H2(g)  C 2 H6(g) If the enthalpy of formation for ethylene is 52.5 kJ mol-1^ and -83.8 kJ mol-1^ for ethane, what is the enthalpy of hydrogenation in kJ mol-1? a. -31.3 b. -136.3 c. 136.3 d. 186.7 e. -186. Part B: True / False (2 points each) Circle either TRUE or FALSE. Unclear responses will be graded as incorrect. 16. Group 1A elements from Na to Cs are all metals. TRUE FALSE 17. Electronegativity in group 2A increases from Be to Ra. TRUE FALSE 18. Bond dissociation energy in group 7A increases from F 2 to I 2. TRUE FALSE 19. Oxide basicity in group 2A increases from Be to Ra. TRUE FALSE 20. Ionic radius in group 7A decreases from F-^ to I-. TRUE FALSE 21. XH 3 hydrides of group 3A elements have octets of valence electrons. TRUE FALSE 22. HF is a weaker acid than HI. TRUE FALSE 23. In group 3A, electronegativity and ionization energy TRUE FALSE decrease from B to Tl. 24. All group 3A elements are metals. TRUE FALSE 25. All group 2A elements are metals. TRUE FALSE

PART B: Problem solving (7 points each) To receive full credit, show all your work and report answers with the correct units and number of significant figures.

26. If the density of strontium is 2.6 g/cm^3 and the edge of its unit cell is 608 pm, does strontium crystallize in a simple cubic lattice or a face-centered cubic lattice? For full credit, provide a mathematical justification for your answer. There are several ways to solve this problem. Here is one way: Volume of unit cell = [608(10-12)m]^3 = 2.25(10-28)m^3 = 2.25(10-23)cm^3 Mass of 1 strontium atom = 87.62 g / mol * 1 / 6.022(10^23 ) atoms / mol = 1.45(10-22) g If Sr is simple cubic, then the unit cells contains 1 atom. If it is fcc, it contains 4 atoms. Dsc = 1.45(10-22) g / 2.25(10-23)cm^3 = 0.65 g / mol Dfcc = 5.81(10-22) g / 2.25(10-23)cm^3 = 2.59 g / mol Sr adopts a fcc cubic packing structure. Alternately, you could calculate the number of atoms in a unit cell using the density. Another way is to calculate the packing efficiency and compare it to the accepted value for fcc. 27. A solution saturated with a salt of the type X 3 Y 2 has an osmotic pressure of 2.64(10-2) atm at 25 C. Assuming ideal behavior, calculate the solubility product (Ksp = [X]^3 [Y]^2 ) for the salt. P = iMRT M = P/iRT = 2.64(10-2) atm / (5 * 0.8206 L atm mol-1^ K-1* 298K) = 2.16(10-4) mol / L M = [X 3 Y 2 ] [X] = 3[X 3 Y 2 ] [Y] = 2[X 3 Y 2 ] Ksp = [X]^3 [Y]^2 = (3[X 3 Y 2 ])^3 * (2[X 3 Y 2 ])^2 = 108[X 3 Y 2 ]^5 Ksp = 108[2.16(10-4) mol / L]^5 = 5.05 (10-17) mol^5 / L^5 5 pts for work. 2 pts for answer. 1 pt for equation. 2 pts for getting M. 2 pts for relating [X3Y2] to [X], [Y]. 2 pts for getting Ksp.