Unformatted text preview: Chem101 (Bontems, Fall 2009, TTH) Exam 4 Name: _______________________ Multiple Choice – In the blank, write the letter of the best answer. (3 pts. ea.) 1.________ The formal charge in the structure shown are a. all are zero b. S = +1, C = ‐1 c. S = +2, C = ‐2 d. e. S = ‐1, C = +1 S = ‐2, C = +2 2.________The bond angle marked in the following molecule is about _________. H
H H N C S
H H a. b. o 90 109o c. d. 120o 180o 3.________Which of the following has the bonds correctly arranged in order of increasing polarity? a. Li‐F < C‐F < O‐F c. O‐F < C‐F < Li‐F b. C‐F < Li‐F < O‐F d. none of these 4. _______ The electron cluster geometry of AsF6‐ ion is octahedral. The hybrid orbitals used by the As atom for bonding are ______. a. sp2 d. sp3d2 e. cannot be determined b. sp3 5 c. sp 5. _______Which of the following substances is least likely to dissolve in water? a. HF c. CH3CH2CH2OH b. CS2 (S=C=S) d. NaBr 6. Which of the following substances would most likely have the lowest viscosity? O a. HOCH2CH2CH2CH2OH c. CH3CH2 C CH2CH3 H
CH3CH2 N CH2CH3 b. CH3CH2CH2CH2CH3 d. 7. _______Which of the molecules in Q6 above will have the highest vapor pressure? 2 8. Consider the following molecules and answer the questions below. (3 pts each) a)
f) Which has higher boiling point, A or B? Which has the lower boiling point, C or D? Which has a higher vapor pressure, E or F? Which molecules (A‐F) would probably dissolve in water? Which compounds above have LDF only? Which compound would have the highest viscosity? 9. Consider the vapor pressure curves below. (6 pts) a. Which compound has the lowest boiling point? b. Estimate the normal boiling point of sample B. Show how you decided. c. Which compound is most likely to have hydrogen bonding as its intermolecular force? 10. Define viscosity and surface tension and explain how these are affected by IMFs. (6 pts) 3 11. Consider the phase diagram shown below. (7 pts) a. Label the phases. b. Estimate the normal freezing point and indicate how you determined this value. c. When a sample of this compound is heated from 0°C to 20°C at a constant pressure of 300 mmHg, what transition occurs? (Give the correct technical term.) d. When the pressure is decreased from 500 to 200 at a constant temperature of 20°C, what transition occurs? (Give the correct technical term.) 12. Describe the intermolecular forces that must be overcome to convert each of the following from a liquid into a gas. Define each force you list. (8 pts) a) CF4 b) NH3 4 13. Rank the following for solubility (H, M, L) and explain your answers by analyzing the solvent and solute IMF’s. Explain the reasoning that you used. (5 pts) Solvent: CO2 (l) (O=C=O) 14. Calculate the pressure required to raise the boiling point of water to 150.0°C, given that the heat of vaporization of water is 41 kJ/mol. (Save the algebra until the end when you are certain you have enough time. (4 pts) 15. For each of the following, a) determine the number of valence electrons, and b) draw a Lewis dot structure which obeys the octet rule. (5 pts each) a. PS2+1 (central atom is P) b. BrS2+1 (central atom is Br) 16. Draw one resonance structure for the following structure connected with the correct symbol. (4 pts) 5 17. For the Lewis dot structures below, give the following information for the atom indicated by the arrow: (6 pts) a. name of the shape b) all bond angles c) hybridization of the atom indicated H3C O CH3
H N O O 18. Give an orbital overlap diagram for the following molecule. Label all orbitals used for bonding, label all bonds as σ or π, and clearly indicate on your diagram expected bond angles. (5 pts) Bonus: If you were present for the demonstrations, describe what you saw and the scientific principle being demonstrated: a. Slime b. Sodium acetate solution poured on table ...
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- Fall '11
- Mole, pts, H3C, correct technical term.