BIOLOGY 100

CHAPTER TWO: THE CHEMICAL BASIS OF LIFE

SELF-DIRECTED STUDY GUIDE

1.What is the atomic mass of an atom that has 19 protons, 20 neutrons and 19 electrons?

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    2. What is a trace element? Cite two examples that can be found in the human body and their purposes served.
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    3. A neutral atom of boron has an atomic number of 5 and an atomic mass of 11. How many electrons does boron have?

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    4. In the equation 2H2 + O2 yields 2H2O, identify A. Only compounds. B. Only molecules. C. both molecule and compound.
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6. What are isotopes? Cite two (2) examples.
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7. A nitrogen atom has 7 protons, and the most common isotope of nitrogen has 7 neutrons. A radioactive isotope of nitrogen has 8 neutrons. What is the atomic number and mass number of this radioactive nitrogen? How does this isotope differ from naturally occurring Nitrogen?

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8. A phosphorus atom contains 15 electrons, 15 protons, and 16 neutrons. What is the mass number of potassium? How many electrons are present on the first shell? The second shell? The third shell?

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9. If one knows the atomic number of an atom, what else does one know?

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10. True or False: A full shell of electrons can be either 2 or 8 depending upon the atom and its number of electrons.
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11. Which of the three elementary subatomic particles is responsible for the chemical properties of an atom? With regard to location, which electrons possess the greatest amount of potential energy?
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 12. What is ionic bonding? How is ionic bonding related to the atoms that are held together in a crystal of table salt?

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13. Sharing of electrons by two or more atoms to form a molecule results in the formation of what kind of bonding pattern: polar covalent bonding, nonpolar covalent bonding, or both? What do the previous types of bonding patterns have in common? How do they differ? BE CAREFUL.
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14. Which of the following would adequately describe what happens when table salt (NaCl) forms? chlorine gives an electron to sodium, sodium gives an electron to chlorine, there is a transfer of electrons, ionic bonding results between sodium and chlorine, sodium and chlorine share electrons to form a bond, a hydrogen bond forms between sodium and chlorine.

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  15 . What is chemically nonsensical about the following structure: H - C=C -H?

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16. In a water molecule, which of the following is true regarding the oxygen atom? It is more positive than the hydrogen atoms. It is more electronegative than the hydrogen atoms. It is electrically neutral.
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17. How are the atoms in a molecule of water held together? How are neighboring molecules of water molecules held together? NOTE: TWO DISTINCT QUESTIONS HAVE BEEN ASKED.
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18. List three(3) properties of water that can be derived from the fact that water molecules are bonded to each other by hydrogen bonds and is a polar molecule.
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B.

C.

19. What property of water is demonstrated in the following situation? After turning the water off at the end of a shower, water still clings to your body.

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20. As ice melts, what happens to the hydrogen bonds?

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21. Which of the following statements about water is/are true? If ice sank, the oceans would eventually freeze solid. Water naturally exists in all three physical states on Earth. Ice is less dense than liquid water. Floating ice on a pond insulates the liquid water below, slowing down its rate of freezing. The hydrogen bonds in ice are less stable than the hydrogen bonds in liquid water.

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22. What is the difference between a base and an acid molecule? NOTE: USE TWO DISTINGUISHING FEATURES IN EACH CASE.)
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23. What is the relationship between each pH unit on the pH scale?
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 24. What pH readings constitute an acid? a base? A neutral substance?
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25. What is the relationship between each pH units and hydrogen ion concentration?
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26. Compare the pH of a solution 4 with a solution of pH 2. The solution of pH 2 is..........

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27. What can be said regarding household ammonia which has a pH of 12 in relationship to household bleach which has a pH of 13?

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 28. Define the term buffer.

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29. In a can of cola, what role does the water serve? What is the role of the sugar? What is the role of the carbon dioxide which makes the coke fizzy and have a tangy taste? What term is used to describe the contents of the can?

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B.

C.

D.

30. The emission of what gases are primarily responsible for acid precipitation or acid rain? B. What are the names of the two acids that form when the two gases react with water.

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