Chem 111 Exam 3 Review Fall 2009 Circle the Correct Response. 1. Which of the following is not a unit of pressure a. Newtons b. Pascal c. mmHg d. Torr e. atm
2. Which of the following gases would have the highest effusion rate at 298K. a. H2 b. N2 c. O2 d. F2 e. Cl2
3. The eqn. of state that is used for a real gas is a. Graham’s . b. Kinetic Theory of Gas c. Charles d. Claussius Clapeyron e. van der Waals
4. The boiling point of water is: a. always 100o C b. lowered by adding a solute to the water. c. the temp. when the atmospheric pressure equals the vapor pressure d. lower than the boiling point of H2S e. all of these.
5. Which of the following would have the highest melting pt? a. CH4 b. SiH4 c. SiCl4 d. GeCl4 e. GeBr4
6. A solid with a high melting point, that does not conduct electricity in its solid or liquid state, is a. network covalent solid b. ionic solid c. metallic solid d. molecular solid e. none of these
7. Which of the following solids should have the highest boiling point? a. H2O b. H2S c. H2Se d. CH4 e. F2
8. Which of the following is not a type of unit cell: a. monoclinic b. cubic c. pentagonal d. orthorhombic e. hexagonal
9. Relates the solubility of a gaseous solute to the partial pressure of the gas above the solution: a. Henry’s Law b. Graham’s Law c. Charles Law d. Boyles Law e. Avogadro’s Law
10. Which of the following solutions will have the lowest freezing point a. a 0.1 m CaCl2 soln b a 0.1 m CaSO4 soln c. a 0.1m sucrose soln. d. a 0.1m NaCl soln e. all have the same freezing point
11. For which of the following does its solubility in water increase with increasing temp. a) Ar(g) b. O2(g) c. NaCl (endothermic mixing) d. Ce2(SeO4)3 (exothermic mixing) e. b and d
12. Virtually all substances that are gases or liquids at room temp and pressure would have a. molecular solids b. metallic solids c. covalent network solids d. ionic solids e. nothing can be determined base on the information. Answer the following problems. Show all work for maximal credit. 1. For the following molecules, name the intermolecular forces each possesses. (3pts) a. H3CF b. H2NNH2 c. O2 d. Which of the above molecules should have the highest boiling pt?
Which has the lowest boiling point?
2. The membrane of blood cell acts as an osmotic membrane. If a blood cell was put into a salt solution whose concentration in moles of particles per kg solvent was greater than the concentration inside of the blood cell, what would happen to the blood cell?
3. Indicate whether the following solids are: molecular, metallic, ionic, or covalent network.. a. NaCl b. N2 c. Cr d. CHCl3 e. AlPO4 f. Boron Nitride (melts at 3000K)
5. In the Claussius Clapeyron Equation:
ln (P2/P1) = Hvap / R) (1/T1 - 1/T2) What does P2 represent? Where is the point (T2,P2) on a phase diagram?
6. Dry ice (solid CO2 Mm = 44.01g/mol) has been used as an “explosive” in mining. A hole is drilled and dry ice and a small amount of gunpowder are placed in the hole with a fuse and the hole is plugged. When lit, the gunpowder rapidly heats the CO2 converting it to vapor. If 440.1g of dry ice are put in a hole of volume 0.5 L and the burning gunpowder heats o the CO2 to 500 C, what is the final pressure inside the hole if it doesn’t blow up? 7. An empty 4.00L steel vessel is filled with 1.00 atm of CH4(g) and 4.00 atm of O2 gas o at 300 C. A spark causes all the CH4 to burn completely according to the eqn: CH4(g) + 2O2(g) -> CO2(g) + 2H2O(g) a. What mass of CO2 is produced by this reaction? b. What is the partial pressure of the CO2(g) in the vessel after the combustion?
8. Krypton crystallizes in a face-centered cubic unit cell of edge 559 pm. a. What is the density of solid krypton? b. Determine the volume of one unit cell. 3 c. What is the volume of one krypton atom? Vsphere = 4/3r d. What percentage of the unit cell volume is occupied by all or part of an atom assuming each atom is a hard sphere? 9. A nonvolatile, molecular substance called “LA” found in coconut oil is used to make detergents. A solution of 5.00g of LA in 100.0g of benzene freezes at 4.1o C whereas o pure benzene freezes at 5.5 C. (Benzene is C6H6; its molar mass is 78.09; Kf = 5.12 o o C/m; Kb = 2.53 C/m) a. What is the value of the freezing point lowering? b. Calculate the molar mass of LA
c. What is the mole fraction LA in the solution? (If you had trouble with part A, assume that the molar mass of LA is 300.0 g/mole.
d. Benzene has a normal boiling point of 80.1o C. For the benzene solution containing LA given above, will the vapor pressure be higher or lower than 1atm? Must state why?
e. What is the vapor pressure of the solution? (assume ideal soln.)
Constants and Equations R = 0.08206 L atm/(mol K) R = 8.31 J/(mol K) R = 1.987 cal/(mol K) ½ ½ o ln(P2/P1) = H/R) (1/T1 - 1/T2) s = 4r/(3) s = 4r/(2) s = 2r P1 = 2 P1 o P1 = 1 P1 T b = i kb m T f = i kf m = iMRT 760 mmHg = 1atm o o o o kb(benzene) = 2.53 C/m kb(water) = 0.52 C/m kf (benzene) = 5.12 C/m kf (water) = 1.86 C/m