Chemistry Homework #12

Pg 233 #1-30

1.     What is a hydrocarbon?

a.     Molecular compounds that only contain atoms of hydrogen and carbon.

    

3.     What characteristics of petroleum make it a valuable resource?

a.     It is a nonrenewable substance, so it can be used for many different products. Examples would be CD’s, sports equipment, clothing, automobile parts, plastic charge cards and carpeting to prescription drugs and artificial limbs.

  

5.     What is meant by saying that oil is crude?

a.     It contains impurities from the ground when it is pumped from the ground

6.     On average, the United States uses about 20 million barrels of petroleum daily:

a.     What is the average number of barrels of petroleum used daily in the United States for building (nonfuel) purposes?

                                               i.     20,000,000 barrels

b.     How many barrels of petroleum, on average, are burned as fuel in the daily United States?

                                               i.     17,800,000 barrels

7.     Name several fuels obtained from crude petroleum.

a.     Heating and cooking fuel, petrochemicals, kerosene, refined oils, gas oils, diesel fuel oil, cracking stock, petroleum jelly, petroleum coke, road oils and asphalt.

8.     A. List four household items made from petroleum.

a.     CD’s, sports equipment, clothing, prescription drugs.

B. What materials could be substituted for each of these four household items if petroleum were not available to make them?

       a.    CD’s can be made out of aluminum, sports equipment could be made out of plastic, clothing could be made out of cotton, and prescription drugs could be made out of other drug substances.

10. A. Which world region has the most petroleum reserves relative to its population?

a.     The Middle East had the most petroleum reserves relative to its population.

B. Which region had the least petroleum reserves relative to its population?

       a.   Central Asia, Far East, and Oceania have the least petroleum reserves

            relative to its population.

11. A. Which regions consume a greater proportion of the world’s supply of petroleum than they posses?

a.     North America, Central Asia, Far East, Oceania, Western and Eastern Europe consume a greater proportion of the world’s supply of petroleum than they posses.

B. Which regions consume a smaller proportion of the world’s supply of petroleum than they posses?

        a.   The Middle East, Africa, and Central and South America consume a smaller proportion of petroleum than they posses.

12. Under what conditions could density be used to separate two different liquids?

a.     If the density of the liquids were insoluble with each other.

13. Referring to Table 3.1 (page 216), a mixture of which two substances listed would be the easiest to separate from each other by distillation? Explain your reasoning.

a.     Acetone and water would be the easiest to separate because they have two completely opposite boiling points; acetone is low, water is high.

15. Referring to Table 3.1 (page 216), sketch a graph of the distillation of a mixture of acetone and water. Label its key features.

16. How does fractional distillation differ from simple distillation?

a.     Simple distillation separates the impurities is in water for example, from salt, while fractional distillation deals with crude oil and can produce many different “fractions” of the oil that can be used for different processes.

17. Petroleum fractions include light, intermediate, and heavy distillates and residues. List three useful products derived from each of these three fractions.

a.     LIGHT: kerosene, refined oils, motor gasoline

b.     INTERMEDIATE: gas oil, petrochemicals, heavy furnace oil

c.      HEAVY: petroleum jelly, lubricating oil and grease, road asphalt

18. Where in a distillation tower—top, middle, or bottom—would you expect the fraction with the highest boiling point range be removed? Why?

a.     In fractional distillation I would expect the bottom to have the highest boiling point because that is the area that is heated by the furnace.

19. After fractional distillation, each fraction is still a mixture. Suggest a way to further separate the components of each fraction.

a.     To further separate, simple distillation could be used.

20. Rank the following straight-chain hydrocarbons from their lowest boiling point to their highest: hexane (C₆H₁₄), methane (CH₄), pentane (C₅H₁₂), and octane (C₈H₁₈). Explain your rankings in terms of intermolecular forces.

a.     Methane (CH₄), Pentane (C₅H₁₂), Hexane (C₆H₁₄), Octane (C₈H₁₈); The lowest boiling points have the weakest carbon bonds because they are smaller or branch out, while the higher boiling points have a stronger attraction among the carbon atoms in the molecule.

21. What is a covalent bond?

a.     A covalent bond is the sharing of two or more valence electrons between two atoms, allowing both atoms to fill their outer shells completely.

22. Why do atoms with filled outer electron shells not form covalent bonds?           

a.     Atoms with filled outer electron shells are stable and do not react with other substances or atoms. Examples would be Helium, Neon, Argon, which are all noble gases.

23. It has been suggested that a covalent bond linking two atoms is like two dogs tugging on the same sock. Explain how this analogy describes the way that shared electrons hold together atoms in a covalent bond.            

a.     The two dogs do not like each other, and therefore, oppose each other, but have a common interest: the sock, similar to the electrons in a covalent bond; they oppose each other but are connected with common electrons in a covalent bond.

  

26. A. What information does a structural formula convey what a molecular formula does not?

a.     A structural formula shows the physical make up of a molecule, but a molecular formula shows the amount of atoms.

B. In what ways is a structural formula an inadequate representation of an actual molecule?

       a.   It is inadequate because it does not show the molecular bonds, but

just the physical makeup.

27. Choose a branched six-carbon hydrocarbon molecule.

a.     Draw a Lewis dot structure to represent its structure.

b.     Draw a structural formula for the same molecule.

28. Each carbon atom has six total electrons. Why, then, does the electron-dot representation of a carbon atom show only four dots?

a.     The four dots represent the number of available electrons to be bonded with in the valence shell.

29.  Use the general molecular formula to write the molecular formula for an alkane containing

a.     9 carbons:

                                               i.     C₉H₂O

b.     16 carbons:

                                               i.     C₁₆H₃₄

c.      10 carbons:

                                               i.     C₁₀H₂₂

d.     18 carbons:

                                               i.     C₁₈H₃₈

30. Calculate the molar mass of each alkane listed in Question 29.

a.     128 grams

b.     226 grams

c.      142 grams

d.     254 grams