Chem 11 - Exam #5 Sample Test

Sample Exams are designed to give you an idea of the types of questions you can expect.  Exam numbers may not exactly agree with currently assigned material, so you may need to examine other sample exams to see questions that might be similar to the upcoming exam. I have made every effort to show correct answers, but there might be an incorrect answer, so if in doubt, you are probably right.

1. Which of the following statements is true?

a. Electrons are never found in an antibonding MO.
b. All antibonding MOs are higher in energy than the atomic orbitals of which they are composed.
c. Antibonding MOs have electron density mainly outside the space between the two nuclei.
d. None of these is true.
e. Two of these statements are true.

2. For NO, draw its (a) Lewis Dot structure, (b) molecular orbital diagram, and (c) indicate bond order. Then, (d) explain why NO is paramagnetic in its lowest energy state.

See Fig. 9.41, page 430 in text

3. Draw correct molecular orbital (M.O.) diagrams for the following, give bond order, and its magnetic properties:

	Bond Order	Paramagnetic or Diamagnetic
H2	1	diamagnetic
H2-	1/2	paramagnetic
O2	2	paramagnetic
O2+	2.5	paramagnetic
O2-	1.5	paramagnetic

4. Which one of the following decreases as the strength of the attractive intermolecular forces increases?

a. The heat of vaporization.
b. The normal boiling temperature.
c. The extent of deviations from the ideal gas law.
d. The sublimation temperature of a solid.
e. The vapor pressure of a liquid.

5. Which statement regarding water is true?

a. Energy must be given off in order to break down the crystal lattice of ice to a liquid.
b. Hydrogen bonds are stronger than covalent bonds.
c. Liquid water is less dense than solid water.
d. Only covalent bonds are broken when ice melts.
e. All of these statements are false.

6. Which of the following statements is false?

a. Diamond is a covalent crystal.
b. The size of the unit cell of Li and Cs is the same.
c. Molecular crystals usually have low melting points.
d. Metallic crystals are usually good electrical conductors.
e. All of the statements are correct.

7. Which of the following statements about steel is false?

a. It contains carbon atoms in the holes of its iron crystals.
b. The presence of carbon-iron bonds in the alloy make steel harder and stronger than pure iron.
c. Pure iron is relatively soft and ductile because it lacks directional bonding.
d. The amount of carbon directly affects the properties of steel.
e. All of these are true.

8. When a nonpolar liquid displays a convex meniscus, which of the following explains this behavior?

a. It has a low surface tension, and therefore clings to the glass.
b. The cohesive forces are stronger than the adhesive forces toward the glass.
c. The adhesive forces toward the glass are stronger than the cohesive forces.
d. The liquid's viscosity is low.
e. none of these

9. Name the following compounds:

    Cl    CH3
     \   /
      C=C          2,3-dichloro-2-butene
     /   \
  H3C     Cl


CH3C=CCH2CH2Cl      5-chloro-2-pentene


 Br H H H Cl
  | | | | |
H-C-C=C-C-C-Cl      1-bromo-5,5-dichloro-2-pentene
  |     | |
  H     H H 

10. The boiling point of methanol is much higher than that of ethane. This is primarily due to

a. the difference in molar masses of methanol and ethane.
b. the hydrogen bonding in methanol.
c. the significant molecular size difference between methanol and ethane.
d. the carbon oxygen double bond in the methanol.
e. none of these.

11. Draw structures which adequately represent each of the following. (see chap 22)

Alkane

Alkene

Aromatic compound

Alcohol

Ether

Carboxylic acid

Ester

12. Teflon is a type of

a. nylon.
b. PVC.
c. elastomer.
d. polymer.

13. Proteins are an amino acid polymers. (a) Show the structure of a "generic" amino acid. Then, (b) show how you produce a peptide bond, and include its structure.

see chapter 23

14. Polar amino acid side chains contain mostly what atoms?

a. carbon and hydrogen
b. nitrogen and oxygen
c. carbon and nitrogen
d. carbon and oxygen
e. nitrogen and hydrogen

15. Which statement is false with respect to proteins?

a. Primary structure refers to the sequence of nucleotides.
b. Secondary structure includes a-helixes.
c. Tertiary structure includes disulfide bonds.
d. The overall shape of a protein is related to the tertiary structure.
e. All are false.

16. What is an enzyme? a biological catalyst

17. Which of the following is not a carbohydrate?

a. sucrose
b. asparagine
c. glycogen
d. starch
e. two of these

18. All of the following statements about carbohydrates are true except which one?

a. They serve as a food structure for most organisms.
b. They are used as a structural material for plants.
c. Many have the empirical formula CH₂O.
d. Starch and cellulose are two important carbohydrates made of monosaccharides.
e. Carbohydrates produce more energy per gram than fats

19. What carbohydrate breaks down rapidly in the body when energy is needed?

a. starch
b. cellulose
c. glycogen
d. sucrose
e. fructose

20. Answer the following TRUE/FALSE questions

_X_T ___F When an electron pair is shared in the area centered on a line joining the atoms a s-bond is formed.
___T _X_F Diamond is a molecular solid.
_X_T ___F Steel is an alloy of carbon and iron.
_X_T ___F All steroids are lipids.
___T _X_F Bond order is the difference between the number of bonding electrons and the number of antibonding electrons.
___T _X_F n-butane and 2-methylpropane exist as geometric isomers

21. Draw and name all structural isomers for hexane (C₆H₁₄).

see chapter 22

22. The structure of salicylic acid is as follows. Starting with salicylic acid, as you did in the lab, (a) show the reaction necessary to produce aspirin (acetylsalicylic acid), (b) what other reagent is needed, (c) list reaction conditions to produce aspirin, and (d) Draw the structure of aspirin.

see chapter 22

23. X-rays of wavelength 1.54 A (A=100 pm) were used to analyze an aluminum crystal. A reflection was produced at q=19.3 degrees. Assuming n=1, calculate the distance d between the planes of atoms producing this reflection. (If you cannot remember the Bragg equation [nl=2d sinq] you can ask me, and I will give it to you, but you will lose 1 point.)

Answer: 233 pm

24. Diamond and graphite, which are both composed of only carbon, have different electrical properties. Which conducts electricity and why?

Graphite conducts electricity, but diamond does not.  Graphite has delocalized electrons in the p-electron cloud which are mobile, but diamond has all its electrons in s-bonds.

25. Under appropriate conditions, show what the product would be for each of the following reactions:

propane + Cl₂ (with UV light) ---> mostly 1-chloropropane and 2-chloropropane

2-butene + Cl₂ ---> 1,2-dichlorobutane

2-butene + HOH ---> 2-butanol

acetic acid + ethanol ---> an ester: ethyl acetate

26. The repeating unit of the DNA polymer is the nucleotide. List the three chemical components that make up the nucleotide.

a sugar (deoxyribose), phosphoric acid (in ester linkages to sugars), and nitrogenous base (A, C, T, or G)