2.E: The Chemical Foundation of Life (Exercises)
2.1: The Building Blocks of Molecules
Multiple Choice
Magnesium has an atomic number of 12. Which of the following statements is true of a neutral magnesium atom?
A. It has 12 protons, 12 electrons, and 12 neutrons.
B. It has 12 protons, 12 electrons, and six neutrons.
C. It has six protons, six electrons, and no neutrons.
D. It has six protons, six electrons, and six neutrons.
- Answer
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A
Atoms that vary in the number of neutrons found in their nuclei are called __________?
A. ions
B. neutrons
C. neutral atoms
D. isotopes
- Answer
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D
Which type of bond represents a weak chemical bond?
A. hydrogen bond
B. ionic bond
C. covalent bond
D. polar covalent bond
- Answer
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A
An isotope of sodium (Na) has a mass number of 22. How many neutrons does it have?
A. 11
B. 12
C. 22
D. 44
- Answer
-
A
Free Response
What makes ionic bonds different from covalent bonds?
- Answer
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Ionic bonds are formed by the strong electrical interaction between ions of opposing charges and are the result of the giving and taking of electrons between atoms. Covalent bonds are formed by the sharing of electrons between atoms and can be either nonpolar (equal sharing) or polar (unequal sharing). Unlike ionic bonds, covalent bonds do not dissociate in water.
Why are hydrogen bonds and van der Waals interactions necessary for cells?
- Answer
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Hydrogen bonds and van der Waals interactions form weak associations between different molecules. They provide the structure and shape necessary for proteins and DNA within cells so that they function properly. Hydrogen bonds also give water its unique properties, which are necessary for life.
2.2: Properties of Water
Multiple Choice
Which of the following statements is not true?
A. Water is polar.
B. Water stabilizes temperature.
C. Water is essential for life.
D. Water is the most abundant atom in Earth’s atmosphere.
- Answer
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D
Which of the following is NOT a property of water essential for life on Earth?
A. Water's adhesive and cohesive nature
B. The increase in density as water freezes to ice
C. Water's high heat capacity
D. The ability of polar water molecules to act as a solvent and dissolve other molecules
- Answer
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B
Using a pH meter, you find the pH of an unknown solution to be 8.0. How would you describe this solution?
A. weakly acidic
B. strongly acidic
C. weakly basic
D. strongly basic
- Answer
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C
The pH of lemon juice is about 2.0, whereas tomato juice's pH is about 4.0. Approximately how much of an increase in hydrogen ion concentration is there between tomato juice and lemon juice?
A. 2 times
B. 10 times
C. 100 times
D. 1000 times
- Answer
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C
Free Response
Why can some insects walk on water?
- Answer
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Some insects can walk on water, although they are heavier (denser) than water, because of the surface tension of water. Surface tension results from cohesion, or the attraction between water molecules at the surface of the body of water [the liquid-air (gas) interface].
Explain why water is an excellent solvent.
- Answer
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Water molecules are polar, meaning they have separated partial positive and negative charges. Because of these charges, water molecules are able to surround charged particles created when a substance dissociates. The surrounding layer of water molecules stabilizes the ion and keeps differently charged ions from reassociating, so the substance stays dissolved.
2.3: Carbon Chemistry
Multiple Choice
Each carbon atom can bond with as many as________ other atom(s) or molecule(s)?
A. 1
B. 2
C. 4
D. 6
- Answer
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C
Which of the following is not a functional group that can bond with carbon?
A. sodium
B. hydroxyl
C. phosphase
D. carbonyl
- Answer
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A
Free Response
What property of carbon makes it essential for organic life?
- Answer
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Carbon's bonding properties are what make it essential for organic life. Carbon's valence electron configuration (4 electrons in its outer shell) make it possible for carbon to form 4 covalent bonds with up to 4 different atoms or molecules. The resulting diversity in molecular form is critical for making the wide variety of biological molecules necessary for life.
Contributors and Attributions
Remixed and/or curated from the following works:
Fowler, S., Roush, R., & Wise, J. (2013). 2.E Chemistry of Life (Excercises) . In Concepts of Biology . OpenStax (CC BY 4.0; Access for free at https://openstax.org/books/concepts-biology/pages/1-introduction ).
Clark, M. A., Douglas, M., & Choi, J. (2018). 1.2.8 Review Questions and 1.2.9 Critical Thinking Questions . In Biology 2e . OpenStax (CC BY 4.0; Access for free at https://openstax.org/books/biology-2e/pages/1-introduction ).