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

Chemistry Homework #11

Pg 361 #14-20

14. Describe how atmospheric CO₂ and water vapor help maintain moderate temperatures at Earth’s surface.

a.     Atmospheric CO₂ and water vapor help maintain moderate temperatures at Earth’s surface because the CO₂ and water vapor absorb the infrared rays the beam down from the sun, but when rays do get through they are reradiated back and retained by the atmosphere.

15. List two natural processes and two human activities that can increase the amount of:

a.     CO₂ in the atmosphere.

                                               i.     HUMAN: clearing forests that would usually consume CO₂ through photosynthesis.

                                              ii.     NATURAL: dead organisms and terrestrial ecosystems (such as trees, crops, and other living matter)

b.     CH₄ in the atmosphere.

                                               i.     HUMAN: burning natural gas

                                              ii.     NATURAL: cows

16. What changes in the composition of the atmosphere would cause the average surface temperature of the Earth to

a.     Increase?

                                               i.     A lower concentration of atmospheric greenhouse gases.

b.     Decrease?

                                               i.     A higher concentration of atmospheric greenhouse gases.

17. Explain why, on a sunny day, a greenhouse with transparent glass walls is much warmer than a structure with opaque wooden walls.

a.     It is much warmer because the infrared rays that come from the sun travel through the glass walls

18. Draw sketches to show how

a.     Greenhouse works.

b.     The global greenhouse works.

19. List three chemical reservoirs of carbon atoms.

a.     Atmospheric CO₂ gas

b.     Solid calcium carbonate (CaCO₃) in limestone

c.      Natural gas (methane, CH₄)

d.     Organic molecules

20. Explain how, over time, a particular carbon atom can be part of the atmosphere, biosphere, lithosphere, and hydrosphere.

a.     Carbon is part of the atmosphere as carbon dioxide gas due to plant photosynthesis, then as limestone in the hydrosphere, and fossil fuels are in the lithosphere. 

The Dawn's Early Light

This article is about how a spacecraft was reaching its destination as the last shuttle left from Florida last week. The space shuttle should be arriving on the second largest asteroid, Vesta, on July 16. Vesta is about 520 kilometers in diameter and is roughly spherical, similar to a planet, due to its gravity. What also makes this asteroid similar to a planet is that it has layers, a mantle and a core. After a year at Vesta, the spacecraft will then travel on to another asteroid, Ceres, the largest asteroid which is 960 kilometers in diameter. It is due to arrive there in 2015. 

Final Blog Post: What i got out of summer Chem

What has been the most valuable learning from summer Chemistry is the periodic table. I learned about how and why elements are named in certain categories such as alkalines, halogens, and noble gases. Also the information about the relation between atomic number and the atomic mass and how the atomic number is the number of protons and electrons, and when you subtract that from the atomic mass, you get the number of neutrons. Also the information about the names of the groups that the elements that are in them and what their charge would be if they were in an ionic state. 

Chemistry Homework #10

Pg 344 #1-4

1.    Why is human exposure to ultraviolet radiation potentially more harmful than exposure to infrared radiation?

a.     Exposure to ultraviolet radiation is potentially more harmful because it is linked to sunburn, skin cancer, and if all the UV radiation reaching the atmosphere actually reached the Earth’s surface, it is likely that the most life on Earth would be destroyed, while infrared radiation can never reach Earth’s surface because it is absorbed carbon dioxide and water vapor.

2.    Describe two essential roles played by visible solar radiation.

a.     Visible radiation helps in the process of plant photosynthesis because it provides the energy needed to react with the chlorophyll molecules.

b.    It also powers the hydrologic cycle because it causes water to evaporate from the oceans and landmasses.

3.    Explain why dry, arid regions in the United States, such as New Mexico and Arizona, experience wider air-temperature fluctuations from night to day than do states with more humid conditions, such as Florida.

a.     Dry, arid regions in the United States experience temperature fluctuations because they don’t have the water or moisture in the atmosphere to absorb the radiation that is traveling to those areas, while more humid areas have less temperature fluctuations because there is more moisture in the air, which absorbs and reradiates the radiation that it comes in contact with.

4.    Suppose Earth had a less dense atmosphere (fewer gas molecules) than it does now:

a.     How would average daytime temperatures be affected? Why?

                                              i.     Yes, it would because the gas would be able to reradiate less thermal energy back to Earth to make it warmer, in which density decreases.

b.    How would average nighttime temperatures be affected? Why?           

                                               i.     Yes, because colder, denser air displaces the warmer air, which cause the warmer air to rise. 

Animations

Chemistry Homework #9

Pg 360 #1-8

1.     Write an equation or a sentence that describes the relationship between the frequency of electromagnetic radiation and its energy.

a.     The relationship between the frequency of electromagnetic radiation and its energy is proportional; if the frequency has a high rate of oscillation (high-frequency radiation) then the amount of energy is high as well.

2.     Why is the word spectrum a good descriptor of the types of energy found in electromagnetic radiation?

a.     The word spectrum is good because it describes a large variety of energy, from low energy to high energy.

3.     Why is visible light useful in plant photosynthesis, while other forms of electromagnetic radiation are not?

a.     Visible light is useful because it reacts with the molecules of chlorophyll, which provides energy in order to produced photosynthesis reactions.

4.     A. List the main types of electromagnetic radiation in order of increasing energy.

a.     UV-A Radiation

b.     UV-B Radiation

c.      UV-C Radiation

B. Describe how each type of radiation listed in your answer to Question 4a affects living things.

       a.    UV-A Radiation has the lowest energy; no effect

       b.    UV-B Radiation has more energy; linked to sunburn and skin cancer.

       c.    UV-C Radiation has the most energy and can break covalent bonds;

             used to sterilize because it can kill bacteria and destroy viruses.

5.     Ultraviolet light is often used to sterilize chemistry laboratory protective goggles. Why is ultraviolet light effective for this use, while visible light is not effective?

a.      It’s frequency radiation, or oscillation levels, are so high that it can kill bacteria.

6.     Compare infrared, visible, and ultraviolet radiation in terms of how well they are absorbed by the atmosphere.

a.     INFRARED: it is well absorbed by the atmosphere; most of the radiation from the sun cannot reach the Earth’s surface because CO2 and gaseous H2O molecules in the atmosphere absorb it.

b.     VISIBLE: not well absorbed; on a clear day, more than 90% of the visible region of solar radiation directed toward Earth travels down to Earth’s surface.

c.      ULTRAVIOLET: well absorbed; most of the UV-B radiation, and much of the UV-A radiation, does not reach Earth’s surface. It is absorbed by the stratospheric ozone layer.

7.     Describe two main effects of the solar radiation that reaches the Earth’s surface.

a.     Maintaining a habitable average temperature on Earth:

                                               i.     The greenhouse gases help to moderate the amount of solar radiation that reaches the Earth’s surface by use of carbon dioxide and water vapor, which readily absorb infrared radiation, for example.

b.     Determining the climates and weather:

                                               i.     Earth’s rotation, yearly revolution, and tilt on its axis. This causes an uneven distribution of solar radiation, which cause the four distinct seasons.

8.     A. Compare lake water and asphalt in terms of how readily each warms up when exposed to sunlight.

a.     The lake water would absorb the infrared radiation and heat up faster because it is similar to clouds, in that clouds are made of droplets of water, but the radiation also powers the hydrologic cycle.

b.     Asphalt would heat up slower because it reradiates the incoming radiation, which helps balance Earth’s energy.

B. What properties of these two materials account for differences in their behavior?

a.     Lake water: absorption of infrared radiation

                  b.  Asphalt: reradiation of incoming radiation.