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Which of the following four statements, if any, is true regarding essential elements and living organisms?
1. The elements carbon, hydrogen, nitrogen, and oxygen make up 20-25% of living mass.
2. Given their low concentrations in nature, the toxicity of some elements is generally not a factor in the evolution of biological communities.
3. Although all forms of life require iron, other elements are required only by certain species.
4. All organisms require 25 of the 92 naturally occurring elements to survive.
5. All of the listed responses are correct.
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3.
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Consider this statement: Concentrations of trace elements in an environment above what is required by organisms generally have no effect on those organisms. Which of the following is a valid response to this statement?
1. False. Elevated concentrations of some trace elements such as cobalt and chromium can be toxic.
2. False. Elevated concentrations of trace elements such as chromium and phosphorus can be toxic.
3. True. Only trace element limitation can lead to disease among organisms.
4. True. Most organisms have evolved adaptations that allow them to tolerate very high concentrations of trace elements in the environment.
5. False. Increasing the concentration of trace elements above what is required generally has a beneficial effect on organisms.
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1.
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Consider this statement: Oxygen is not a greenhouse gas; therefore, gases containing oxygen—such as ozone, nitrous oxide, and carbon dioxide—are not greenhouse gases either. Which of the following is a valid response to this statement?
1. True. Compounds display emergent properties that are very similar to those of the elements that form them.
2. False. Compounds can have emergent properties that are very different from those of the elements that form them.
3. False. Oxygen is a special case because of its reactivity and electronegativity.
4. True. Because oxygen is not a greenhouse gas, it is unlikely to combine with anything at a higher level of organization to form a greenhouse gas.
5. True. It is impossible for a gas containing oxygen to be a greenhouse gas.
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2.
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There are __________ naturally occurring elements.
1. 4
2. 25
3. 92
4. 108
5. 238
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3.
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Which of the following is a trace element?
1. copper
2. oxygen
3. hydrogen
4. carbon
5. nitrogen
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1.
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What are the four most abundant elements found in living systems?
1. hydrogen, oxygen, calcium, and nitrogen
2. hydrogen, oxygen, nitrogen, and carbon
3. magnesium, calcium, iron, and zinc
4. nitrogen, carbon, sulfur, and oxygen
5. hydrogen, oxygen, nitrogen, and carbon dioxide
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2.
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Which of the following has negligible mass?
1.element
2. neutron
3. proton
4. electron
5. atom
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4.
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Which of the following subatomic particles has appreciable mass and lacks a charge?
1. element
2. molecule
3. proton
4. neutron
5. electron
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4.
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The number of protons in an uncharged atom __________.
1. determines the atom’s mass number
2. equals the number of electrons
3. varies with the different isotopes
4. equals the number of neutrons
5. equals the number of electrons in the outer orbital of the atom
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2.
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An element has eight protons, nine neutrons, and eight electrons. Its atomic number and atomic mass, respectively, are __________.
1. 8 and 16
2. 8 and 17
3. 9 and 16
4. 9 and 17
5. 16 and 8
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2.
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An uncharged atom of nitrogen (atomic number = 7) has __________.
1. seven valence electrons
2. seven protons and seven electrons
3. seven protons and seven neutrons
4. seven neutrons and seven electrons
5. seven neutrons
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2.
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In which of the following will isotopes of an element always differ?
1. number of protons
2. atomic number
3. number of electrons
4. atomic mass
5. None of the listed responses is correct.
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4.
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A particular carbon isotope has an atomic number of 6 and an atomic mass of 14. The respective number of neutrons, protons, and electrons that this carbon isotope has is __________.
1. 6, 8, and 6
2. 8, 6, and 8
3. 8, 6, and 4
4. 6, 6, and 8
5. 8, 6, and 6
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5.
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Phosphorus-32 (radioactive) has __________ than phosphorus-35 (normal).
1. three more atoms
2. three more protons
3. three fewer neutrons
4. three more neutrons
5. three fewer protons
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3.
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The most common form of calcium has 20 protons, 20 neutrons, and 20 electrons. Which of the following elements would be an isotope of calcium?
1. an atom with 20 protons, 21 neutrons, and 20 electrons
2. an atom with 21 protons, 21 neutrons, and 21 electrons
3. an atom with 21 protons, 20 neutrons, and 21 electrons
4. an atom with 20 protons, 20 neutrons, and 18 electrons
5. All of the listed responses are correct.
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1.
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Why are radioactive isotopes useful in scientific research?
1. because they are difficult to detect in small amounts, but living cells cannot distinguish them from the corresponding stable isotopes
2. because they decay spontaneously and give off energy and subatomic particles
3. because they are not readily incorporated into biological reactions
4. because they can be used as tracers to follow particular atoms and molecules through metabolic pathways
5. All of the listed responses are correct.
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4.
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A neutral atom of chlorine has an atomic number of 17. It has __________ electrons in its third shell.
1. 2
2. 7
3. 8
4. 10
5. 17
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2.
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The chemical characteristics or reactivity of an element depend mostly on the __________.
1. mean energy level of its electrons
2. degree to which it has more or fewer electrons than protons
3. number of electrons in its outermost shell
4. number of protons plus the number of neutrons
5. number of electron shells present in the atoms
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3.
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Some groups of elements react chemically in similar ways. For example, the chemistry of sodium and the chemistry of lithium are similar. The chemistry of chlorine and the chemistry of iodine are also similar. These similarities in chemistry result when different elements have similar __________.
1. atomic size
2. numbers of outer-shell electrons
3. atomic numbers
4. energy per electron
5. total numbers of electrons
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2.
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How many electrons would be present in the valence shell of a sulfur atom (atomic number 16, mass number 32)?
1. one electron
2. two electrons
3. four electrons
4. six electrons
5. eight electrons
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4.
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For most atoms, when is a stable configuration of electrons attained?
1. when the atom has eight electrons in its outermost shell
2. when the atom has as many protons as neutrons
3. when the atom has moved all its electrons to its outermost shell
4. when the atom achieves a zero net charge
5. None of the listed responses is correct.
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1.
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An atom that normally has __________ in its outer shell would NOT tend to form chemical bonds with other atoms.
1. one electron
2. three electrons
3. four electrons
4. six electrons
5. eight electrons
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5.
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Consider a hypothetical atom with an atomic number of 4 and a net charge of +1. How many neutrons does this ion have?
1. one
2. three
3. four
4. The answer cannot be determined from the information provided.
5. None of the listed responses is correct.
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4.
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When one or more pairs of valence electrons are shared by two neutral atoms, what type of bond is formed?
1. a neutral bond
2. an ionic bond
3. a covalent bond
4. a hydrogen bond
5. an electronegative bond
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3.
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A covalent bond is likely to be polar if __________.
1. it is between two atoms that are both very strong electron acceptors
2. the two atoms sharing electrons are equally electronegative
3. the two atoms sharing electrons are of the same element
4. one of the atoms sharing electrons is much more electronegative than the other
5. it is between two atoms that are both very strong electron donors
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4.
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When the proton number and electron number are unequal, the atom or molecule __________.
1. forms a covalent bond with another atom
2. gains or loses a proton
3. becomes part of a molecule
4. is an ion
5. gains or loses a neutron
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4.
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Copper has an atomic number of 29 and a mass number of 64. What would result if an uncharged copper atom lost two electrons?
1. The atomic number would remain 29, the mass number would remain 64, and the atom would be a cation with a +2 charge.
2. The atom would have a double negative charge and be an ion.
3. The atomic number of the atom would remain 29, the mass number would be reduced to 62, and the atom would be an anion.
4. The atomic number would remain 29, the mass number would increase to 66, and the atom would be a cation with a -2 charge.
5. The atomic number would be reduced to 27, the mass number would remain 64, and the atom would be an anion with a +2 charge.
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1.
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The compound CaSO4 ionizes into a calcium ion and a sulfate ion (SO4). Calcium has two electrons in its outer shell. Upon ionization, what would you expect the charge on the sulfate ion to be?
1. -4
2. -2
3. -1
4. +1
5. +2
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2.
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Ionic bonds form as a result of __________.
1. attraction between a hydrogen and other atoms that share electrons unequally
2. the asymmetric distribution of electrons in constant motion
3. sharing of electron pairs between atoms
4. attraction between ions that have opposite charges
5. unequal sharing of electrons between atoms
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4.
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A hydrogen bond __________.
1. is a weak chemical bond
2. is a function of hydrophobic interactions
3. is one in which hydrogen is strongly attracted to a positively charged atom
4. is a strong chemical bond
5. is one in which two hydrogen atoms bond to each other
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1.
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When do hydrogen bonds occur?
1. when two atoms achieve stable electron configurations by sharing electrons with each other
2. when a molecule with a low molecular weight is bonded to a molecule with a high molecular weight
3. when partial opposite charges on molecules come close enough to attract each other
4. when a molecule with partial charges contacts a molecule without partial charges
5. None of the listed responses is correct.
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3.
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What is the role of van der Waals interactions in biological molecules?
1. Van der Waals interactions are strong bonds that play a major structural role in holding proteins together.
2. Although they are weak bonds, van der Waals interactions involve the sharing of electrons.
3. Van der Waals interactions are important only in water.
4. Although they are weak bonds, van der Waals interactions help to reinforce the three-dimensional shapes of large molecules.
5. Van der Waals interactions are too weak to be significant.
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4.
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Which of the following molecules has the shape of a completed tetrahedron?
1. oxygen gas (O2)
2. glucose (C6H12O6)
3. water (H2O)
4. hydrogen gas (H2)
5. methane (CH4)
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5.
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Pharmaceutical researchers are often interested in blocking particular receptor proteins on cell surfaces. What chemical property of a molecule would be most important for this type of application?
1. the type of bonding in the molecule
2. the number of valence electrons
3. the molecule’s shape
4. the atomic numbers of the atoms involved
5. the number of double bonds in the molecule
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3.
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Which of the following statements is true about chemical reactions?
1. They may have different numbers of a given atom on each side of the equation arrow.
2. They involve the making and breaking of chemical bonds.
3. They represent the way matter is created and destroyed.
4. Only inorganic molecules can participate in chemical reactions.
5. They reach chemical equilibrium when the amounts of products and reactants are equal
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2.
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Which of the following statements describes a reversible reaction that has reached chemical equilibrium?
1. The rate of the reverse reaction equals the rate of the forward reaction.
2. The concentration of the reactants is equal to the concentration of the products.
3. The forward and the reverse reactions have stopped.
4. The rate of the forward reaction exceeds the rate of the reverse reaction.
5. The rate of the reverse reaction exceeds the rate of the forward reaction.
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1.
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