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Problem Set for 3rd Long Exam due: 09 October 2009Some topics are not discussed (yet). Do read on them.

On Molecular Orbitals

1. What is the molecular orbital configuration of Ne2? (1pt)

2. What is the bond order of F2+? (1pt)

3. Between O2 and O22+, which is diamagnetic? (1pt)

On Condensed Phases: Solids and Liquids

1. Unit cells are the repeating structures of what particular solids? (1pt)2. Among the types of solids according to bond between particles, which is expected

to only conduct electricity when dissolved in water? (1pt)3. Increase or decrease: What happens to the energy gap as one goes from

insulating to conducting solids? (1pt)

4. Increase or decrease: As the strength of intermolecular forces of attractionincreases, what happens to viscosity and surface tension properties ofsubstances? (1pt)

5. Increase or decrease: As the molecular weight increases, what happens to the

boiling point of non polar linear substances? (1pt)6. NaF or KF: Which will exhibit a higher melting property? (1pt)

On Heat Transfer & Phase Diagrams

Consider the phase diagram shown for #s 1-3,1. The substance is in what state (solid, liquid or gas)

at room temperature and sea-level pressure? (1pt)2. What phase change happens at 30C and 1atm?

(1pt)3. What are the critical temperature and critical

pressure values for the substance? (1pt)4. Calculate the mass (in g) of H2O at 50.0

oCconverted to steam at 120oC if 1000.0 kJ of

energy is absorbed. The molar heat of vaporizationof water is 40.7 kJ/mol and the molar heatcapacities of liquid water and steam are 75.3 J/mol-oC and 36.4 J/mol-oC,respectively. (2pts)

5. What is the normal atmospheric pressure of a certain high-altitude place if thewater boils at 94oC in that area? The molar heat of vaporization of water is 40.7kJ/mol. (2pts)

On Gases

1. Three 5-L flasks, fixed with pressure gauges and small valves, each contain 4g of

gas at 273 K. Flask A contains H2, flask B contains He and flask C contains CH4.Rank flask contents in terms of

a. pressure *answer: A > B > Cb. diffusion rate after the valve is opened (1pt)

c. total kinetic energy of the molecules (1pt)d. density (1pt)

* answer is provided for (a) to set an example. use >, =, and < signs only.

2. For each of the following, which shows the greater deviation from ideal behaviorat the same set of conditions?

a. argon or xenon (1pt)b. water vapor or neon (1pt)

c. mercury vapor or CH4 (1pt)

Pressure

Temperature

1 atm

30C13C

0.9 atm

1.15 atm

39

C

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3. A sample of a liquid hydrocarbon known to consist of molecules with five carbonatoms is vaporized in a 0.204-L flask by immersion in a water bath at 1010C. The

barometric pressure is 767 torr, and the remaining gas condenses to 0.482 g ofliquid. What is the molecular formula of the hydrocarbon? (3pts)

4. Hemoglobin is the protein that transports O2 through the blood from the lungs tothe rest of the body. In doing so, each molecule of hemoglobin combines with

four molecules of O2. If 1.00 g of hemoglobin combines with 1.53 mL of O2 at

37.00C and 743 torr, what is the molar mass of hemoglobin? (3pts)Hm + 4O2(g) Hm(O2)4

On Solutions

1. A mixture which contains 0.550 g camphor and 0.045 g of an organic solute

freezes1t 157.0 deg C. The solute contains 93.46% of C and 6.54% of H byweight. What is the molecular formula of the compound? Given: Kfof camphor =37.7 deg C/molal, and Tfof camphor = 178.4 deg C. (3pts)

2. A solution of an unknown non-volatile non-electrolyte was prepared by dissolving0.250 g of the substance in 40.0 g of CCl4. The boiling point of the resultantsolution was 0.357 deg C higher than that of the pure solvent. Calculate themolar mass of the solute. (Kb for CCl4 = 5.02 deg C/molal) (3pts)

3. The osmotic pressure of 0.010 M solution of CaCl2 and urea at 25

0

C are 0.605 and0.245 atm, respectively. Calculate the vant Hoff factor for CaCl2. (3pts)

On Acids & Bases

1. Given the following reactions, arrange the acids [HCOOH, H2S, HBrO, (COOH)2,C6H5OH] in order of increasing acid strength. (5pts)

NaBrO + C6H5OH no reaction2 NaBrO + H2S 2 HBrO + Na2S

H2S + 2 C6H5ONa 2 C6H5OH + Na2S

H2S + HCOONa no reaction2 HCOONa + (COOH)2 2 HCOOH + (COONa)2

2. With the concept of conjugate acid/base pair, arrange the conjugate bases of theabove acids in order of increasing basic property. (5pts)

3. A solution was tested to be of pH = 4.38. If 15.0 mL of 0.100 M of KOH wasadded to 25.0 mL of H2SO4 to prepare the given solution, what is theconcentration of the acid used? (3pts)

The dictionary is the only place where success comes before work.The dictionary is the only place where success comes before work.The dictionary is the only place where success comes before work.The dictionary is the only place where success comes before work. ---- Mark TwaiMark TwaiMark TwaiMark Twainnnnchem16:gee_lian