Water and Carbon (The Chemical Bases of Life): Chapter 2 Comprehensive Exam Study Guide, Exams of Biology

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Water and Carbon (Thechemical

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1. How many electrons are involved in a single covalent bond? A) one B) two C) three D) four Answer: B Reference: Section 2. Bloom's Level: Remembering LOs: Chp2-1. Explain how and why atoms interact to form molecules. Sketch examples of how electrons are shared in nonpolar covalent bonds, polar covalent bonds, and ionic bonds.

2. How many electrons are involved in a double covalent bond? A) one B) two C) three D) four Answer: D Reference: Section 2. Bloom's Level: Remembering LOs: Chp2-1. Explain how and why atoms interact to form molecules. Sketch examples of how electrons are shared in nonpolar covalent bonds, polar covalent bonds, and ionic bonds.

3. How many electrons are involved in a triple covalent bond? A) two B) three C) six D) nine Answer: C Reference: Section 2. Bloom's Level: Remembering LOs: Chp2-1. Explain how and why atoms interact to form molecules. Sketch examples of how electrons are shared in nonpolar covalent bonds, polar covalent bonds, and ionic bonds.

4. If an atom has a charge of +1, which of the following must be true? A) It has two more protons than neutrons. B) It has the same number of protons as electrons.

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B) It has two more protons than electrons. C) It has two more protons than neutrons. D) It has two more neutrons than electrons. Answer: A Reference: Section 2. Bloom's Level: Comprehension LOs: Chp2-1. Explain how and why atoms interact to form molecules. Sketch examples of how electrons are shared in nonpolar covalent bonds, polar covalent bonds, and ionic bonds.

6. If an atom is electrically neutral, which of the following must be true? A) It has the same number of protons as neutrons. B) It has the same number of protons as electrons. C) It has the same number of neutrons as electrons. D) It has at least one more electron than it has protons. Answer: B Reference: Section 2. Bloom's Level: Comprehension LOs: Chp2-1. Explain how and why atoms interact to form molecules. Sketch examples of how electrons are shared in nonpolar covalent bonds, polar covalent bonds, and ionic bonds.

7. An atom has six electrons in its valence shell. How many single covalent bonds would you expect it to form in most circumstances? A) one B) two C) three D) six Answer: B Reference: Section 2. Bloom's Level: Comprehension LOs: Chp2-1. Explain how and why atoms interact to form molecules. Sketch examples of how electrons are shared in nonpolar covalent bonds, polar covalent bonds, and ionic bonds.

8. An atom has four electrons in its valence shell. What types of covalent bonds is it capable of forming? A) single, double, or triple B) single and double only C) four single bonds only

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D) two double bonds only Answer: A Reference: Section 2. Bloom's Level: Comprehension LOs: Chp2-1. Explain how and why atoms interact to form molecules. Sketch examples of how electrons are shared in nonpolar covalent bonds, polar covalent bonds, and ionic bonds.

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B) a hydrogen bond C) a nonpolar covalent bond D) a polar covalent bond Answer: D Reference: Section 2. Bloom's Level: Remembering LOs: Chp2-1. Explain how and why atoms interact to form molecules. Sketch examples of how electrons are shared in nonpolar covalent bonds, polar covalent bonds, and ionic bonds.

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13. When the atoms involved in a covalent bond have the same electronegativity, what type of bond results? A) an ionic bond B) a hydrogen bond C) a nonpolar covalent bond D) a polar covalent bond Answer: C Reference: Section 2. Bloom's Level: Remembering LOs: Chp2-1. Explain how and why atoms interact to form molecules. Sketch examples of how electrons are shared in nonpolar covalent bonds, polar covalent bonds, and ionic bonds.

14. The difference between a polar covalent bond and an ionic bond is that electrons are shared unequally in a polar covalent bond, but are completely transferred (i.e., not shared) in an ionic bond. A) true B) false Answer: A Explanation: A) This would be a good classroom discussion question to drive home this important but subtle point. Reference: Section 2. Bloom's Level: Remembering LOs: Chp2-1. Explain how and why atoms interact to form molecules. Sketch examples of how electrons are shared in nonpolar covalent bonds, polar covalent bonds, and ionic bonds.

15. Nitrogen (N) normally forms only three covalent bonds because it has a valence of five. However, ammonium has four covalent bonds, each to a different hydrogen (H) atom (H has a valence of one). Make a sketch of this molecule. Count the number of electrons in your sketch. Compare this number to the number of valence electrons in one N and four H's. What is the charge on this molecule most likely to be? A) + B) - C) + D) - Answer: A Reference: Section 2. Bloom's Level: Applying

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16. The structural formula for a certain molecule includes a group symbolized -O. The dash next to the oxygen atom means that a single bond exists to another atom, such as a carbon. Based on the valence of oxygen and the number of bonds it normally forms, what is the charge on the oxygen atom in this case? A) + B) - C) + D) - Answer: B Explanation: B) This question is rather difficult, and easy to misinterpret. Instructors should use it as an exam question only if they have emphasized this concept in class. Otherwise, it would make an excellent in-class question to promote discussion on why certain atoms in molecules have a charge and others do not. Reference: Section 2. Bloom's Level: Applying LOs: Chp2-1. Explain how and why atoms interact to form molecules. Sketch examples of how electrons are shared in nonpolar covalent bonds, polar covalent bonds, and ionic bonds.

17. You need to write down information about a molecule, but need to indicate only which atoms it contains and how many of each. Which representation would work best? A) molecular formula B) structural formula C) ball-and-stick model D) space-filling model Answer: A Reference: Section 2. Bloom's Level: Remembering LOs: Chp2-1. Explain how and why atoms interact to form molecules. Sketch examples of how electrons are shared in nonpolar covalent bonds, polar covalent bonds, and ionic bonds.

18. You need to write down information about a molecule that gives the most accurate picture of the relative sizes of the atoms involved and their relationship in space. Which representation would work best? A) molecular formula B) structural formula C) ball-and-stick model D) space-filling model

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Answer: D Explanation: D) In-class discussion could be accompanied by pictures of ball-and-stick and space-filling models to stress the advantages of space-filling models. Reference: Section 2. Bloom's Level: Remembering LOs: Chp2-1. Explain how and why atoms interact to form molecules. Sketch examples of how electrons are shared in nonpolar covalent bonds, polar covalent bonds, and ionic bonds.

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C) Its heat of vaporization is lower than that of most other substances. D) It is polar. Answer: C Reference: Section 2. Bloom's Level: Remembering LOs: Chp2-2. List the unusual properties of water. Explain how these properties relate to the structure of water molecules, and how they make water important for life.

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23. Which of the following true statements can be attributed to water's high specific heat? A) Oil and water do not mix well. B) Our body temperature takes a long time to change because it is composed mostly of water. C) Ice floats on water. D) Sugar dissolves in hot tea faster than in iced tea. Answer: B Reference: Section 2. Bloom's Level: Remembering LOs: Chp2-2. List the unusual properties of water. Explain how these properties relate to the structure of water molecules, and how they make water important for life.

24. The ability to sweat or pant is considered an adaptation. Why? A) It allows a body to release excess water. B) It allows a body to absorb heat, due to water's high specific heat. C) It cools a body off, due to water's high heat of vaporization. D) It is an important signal to others that an individual is too hot. Answer: C Reference: Section 2. Bloom's Level: Comprehension LOs: Chp2-2. List the unusual properties of water. Explain how these properties relate to the structure of water molecules, and how they make water important for life.

25. The cities of Portland, Oregon, and Minneapolis, Minnesota, are at about the same latitude, but Minneapolis has much hotter summers and much colder winters than Portland. Why? (Portland is near the Pacific Ocean; Minneapolis is near a number of large lakes.) A) They are not at exactly the same latitude. B) The ocean is so large that it has a highly moderating influence on temperature. C) Freshwater is more likely to freeze than saltwater. D) Minneapolis is much windier, due to its location in the middle of a continent. Answer: B Reference: Section 2. Bloom's Level: Comprehension LOs: Chp2-2. List the unusual properties of water. Explain how these properties relate to the structure of water molecules, and how they make water important for life.

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water freezing from the top down, and cells rupturing from inside out due to water freezing, are important and worth noting now. Reference: Section 2. Bloom's Level: Remembering LOs: Chp2-2. List the unusual properties of water. Explain how these properties relate to the structure of water molecules, and how they make water important for life.

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29. A pH of 7 is neutral due to the dissociation of water molecules in pure water. How many molecules of water have broken down into a hydroxide ion and a hydronium ion at pH 7? A) 1 in 1 million B) 1 in 10 million C) 1 in 100 million D) 1 in 1 billion Answer: B Explanation: B) no other questions on pH, this questions makes student recast the information in different units Reference: Section 2. Bloom's Level: Comprehension LOs: Chp2-2. List the unusual properties of water. Explain how these properties relate to the structure of water molecules, and how they make water important for life.

30. A solution with a pH of 5 has how many more protons in it than a solution with a pH of 7? A) 5 times B) 10 times C) 100 times D) 1,000 times Answer: C Explanation: C) Introduces log nature of pH scale Reference: Section 2. Bloom's Level: Comprehension LOs: Chp2-2. List the unusual properties of water. Explain how these properties relate to the structure of water molecules, and how they make water important for life.

31. Consider the following reaction at equilibrium: CO2 + H2O ↔ H2CO3. What would be the

effect of adding additional H2CO3? A) It would drive the equilibrium dynamics to the right. B) It would drive the equilibrium dynamics to the left. C) Nothing would happen, because the reactants and products are in equilibrium. D) The amounts of CO2 and H2O would decrease.

Answer: B Explanation: B) This would be a good question to stimulate discussion on equilibrium and starting dynamics, ratios, and absolute quantities. Reference: Section 2. Bloom's Level: Comprehension

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32. Which of the following is a violation of the first law of thermodynamics? A) The amount of energy stored in a plant's cell as sugars after undergoing photosynthesis is less than the amount of sunlight it absorbed. B) A hydrogen bomb can destroy a large city with only a few pounds of explosive material. C) All of the energy in the universe today was present when the Big Bang occurred. D) The universe will eventually die, and it will have no energy left in it. Answer: D Explanation: D) This question could generate a lot of classroom discussion. Reference: Section 2. Bloom's Level: Comprehension LOs: Chp2-3. Define energy, and describe the major forms it can take. Explain why chemical bonds can be considered a form of energy.

33. Which reaction is most spontaneous? A) a reaction that is slightly exothermic and leads to a slight increase in entropy B) a reaction that is slightly endothermic and leads to a huge decrease in entropy C) a reaction that is highly exothermic and leads to a huge decrease in entropy D) a reaction that is slightly exothermic and leads to a huge increase in entropy Answer: D Explanation: D) This would be a good Classroom Response System (CRS) question. Wrong answers on this question can be very instructive. Reference: Section 2. Bloom's Level: Comprehension/Remembering LOs: Chp2-3. Define energy, and describe the major forms it can take. Explain why chemical bonds can be considered a form of energy.

34. Why are some reactions exothermic? A) The products have lower potential energy than the reactants. B) They are spontaneous. C) They are nonspontaneous. D) The products have higher entropy (are more disordered) than the reactants. Answer: A Reference: Section 2. Bloom's Level: Remembering LOs: Chp2-3. Define energy, and describe the major forms it can take. Explain why chemical bonds can be considered a form of energy.

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35. Ice melts spontaneously at room temperature, even though the process is endothermic. How is this possible? A) ΔH is small, so melting still obeys the second law of thermodynamics. B) The Gibbs free-energy relationship does not apply to phase changes such as melting. C) Water has a very high specific heat. D) There is a large increase in entropy. Answer: D Reference: Section 2. Bloom's Level: Remembering LOs: Chp2-3. Define energy, and describe the major forms it can take. Explain why chemical bonds can be considered a form of energy.

36. What does it mean to say a system has a ∆G equal to zero? A) The system does not release or absorb heat. B) The system is perfectly ordered (no entropy). C) The total amount of potential energy in the system is zero. D) The system is at equilibrium. Answer: D Reference: Section 2. Bloom's Level: Remembering LOs: Chp2-3. Define energy, and describe the major forms it can take. Explain why chemical bonds can be considered a form of energy.

37. In the Gibbs free-energy relationship, why is the T term necessary? A) The free-energy change caused by a change in entropy is a function of temperature. B) The free-energy change caused by a change in potential energy is a function of temperature. C) The free-energy change caused by a change in electrical charge is a function of temperature. Answer: A Reference: Section 2. Bloom's Level: Remembering LOs: Chp2-3. Define energy, and describe the major forms it can take. Explain why chemical bonds can be considered a form of energy.

38. Which statement best summarizes the essence of chemical evolution? A) Energy in the form of sunlight or heat was transformed into chemical energy. B) Instead of being radiated back to space, energy in the form of sunlight or heat was retained in the oceans and atmosphere because of water's high specific heat.