Practice Test 3/5/23, 3:30 PM Practice Test This activity contains 36 questions. Which of the following four statements, if any, is true regarding essential elements and living organisms? ( Concept 2.1) All organisms require 25 of the 92 naturally occurring elements to survive. The elements carbon, hydrogen, nitrogen, and oxygen make up 20–25% of living mass. Although all forms of life require iron, other elements are required only by certain species. Given their low concentrations in nature, the toxicity of some elements is generally not a factor in the evolution of biological communities. All of the listed responses are correct. 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? ( Concept 2.1) False. Increasing the concentration of trace elements above what is required generally has a beneficial effect on organisms. False. Elevated concentrations of some trace elements such as cobalt and chromium can be toxic. True. Most organisms have evolved adaptations that allow them to tolerate very high concentrations of trace elements in the environment. False. Elevated concentrations of trace elements such as chromium and phosphorus can be toxic. True. Only trace element limitation can lead to disease among organisms. 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? ( Concept 2.1) False. Oxygen is a special case because of its reactivity and electronegativity. True. Compounds display emergent properties that are very similar to those of the elements that form them. https://wps.pearsoncustom.com/pls_1269930281_campbell_biology_hcc/245/62942/16113201.cw/index.html Page 1 of 11 Practice Test 3/5/23, 3:30 PM False. Compounds can have emergent properties that are very different from those of the elements that form them. True. It is impossible for a gas containing oxygen to be a greenhouse gas. 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. There are __________ naturally occurring elements. ( Concept 2.1) 4 25 92 108 238 Which of the following is a trace element? ( Concept 2.1) nitrogen oxygen carbon copper hydrogen What are the four most abundant elements found in living systems? ( Concept 2.1) hydrogen, oxygen, nitrogen, and carbon magnesium, calcium, iron, and zinc nitrogen, carbon, sulfur, and oxygen hydrogen, oxygen, calcium, and nitrogen hydrogen, oxygen, nitrogen, and carbon dioxide Which of the following has negligible mass? ( Concept 2.2) https://wps.pearsoncustom.com/pls_1269930281_campbell_biology_hcc/245/62942/16113201.cw/index.html Page 2 of 11 Practice Test 3/5/23, 3:30 PM proton electron element atom neutron Which of the following subatomic particles has appreciable mass and lacks a charge? ( Concept 2.2) molecule proton element electron neutron The number of protons in an uncharged atom __________. ( Concept 2.2) equals the number of electrons in the outer orbital of the atom varies with the different isotopes equals the number of electrons determines the atom’s mass number equals the number of neutrons An element has eight protons, nine neutrons, and eight electrons. Its atomic number and atomic mass, respectively, are __________. ( Concept 2.2) 8 and 16 8 and 17 9 and 16 9 and 17 16 and 8 An uncharged atom of nitrogen (atomic number = 7) has __________. ( https://wps.pearsoncustom.com/pls_1269930281_campbell_biology_hcc/245/62942/16113201.cw/index.html Concept 2.2) Page 3 of 11 Practice Test 3/5/23, 3:30 PM seven protons and seven neutrons seven neutrons and seven electrons seven neutrons seven protons and seven electrons seven valence electrons In which of the following will isotopes of an element always differ? ( Concept 2.2) atomic mass atomic number number of protons number of electrons None of the listed responses is correct. 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 __________. ( Concept 2.2) 6, 6, and 8 8, 6, and 6 6, 8, and 6 8, 6, and 4 8, 6, and 8 Phosphorus-32 (radioactive) has __________ than phosphorus-35 (normal). ( Concept 2.2) three more neutrons three fewer protons three more atoms three fewer neutrons three more protons https://wps.pearsoncustom.com/pls_1269930281_campbell_biology_hcc/245/62942/16113201.cw/index.html Page 4 of 11 Practice Test 3/5/23, 3:30 PM 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? ( Concept 2.2) an atom with 21 protons, 20 neutrons, and 21 electrons an atom with 21 protons, 21 neutrons, and 21 electrons an atom with 20 protons, 21 neutrons, and 20 electrons an atom with 20 protons, 20 neutrons, and 18 electrons All of the listed responses are correct. Why are radioactive isotopes useful in scientific research? ( Concept 2.2) because they decay spontaneously and give off energy and subatomic particles because they are not readily incorporated into biological reactions because they can be used as tracers to follow particular atoms and molecules through metabolic pathways because they are difficult to detect in small amounts, but living cells cannot distinguish them from the corresponding stable isotopes All of the listed responses are correct. A neutral atom of chlorine has an atomic number of 17. It has __________ electrons in its third shell. ( Concept 2.2) 2 7 8 10 17 The chemical characteristics or reactivity of an element depend mostly on the __________. ( Concept 2.2) number of electrons in its outermost shell number of electron shells present in the atoms mean energy level of its electrons https://wps.pearsoncustom.com/pls_1269930281_campbell_biology_hcc/245/62942/16113201.cw/index.html Page 5 of 11 Practice Test 3/5/23, 3:30 PM degree to which it has more or fewer electrons than protons number of protons plus the number of neutrons 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 __________. ( Concept 2.2) atomic size total numbers of electrons energy per electron numbers of outer-shell electrons atomic numbers How many electrons would be present in the valence shell of a sulfur atom (atomic number 16, mass number 32)? ( Concept 2.2) one electron two electrons four electrons six electrons eight electrons For most atoms, when is a stable configuration of electrons attained? ( Concept 2.2) when the atom has moved all its electrons to its outermost shell when the atom has as many protons as neutrons when the atom achieves a zero net charge when the atom has eight electrons in its outermost shell None of the listed responses is correct. An atom that normally has __________ in its outer shell would NOT tend to form chemical bonds with other atoms. ( Concept 2.2) one electron https://wps.pearsoncustom.com/pls_1269930281_campbell_biology_hcc/245/62942/16113201.cw/index.html Page 6 of 11 Practice Test 3/5/23, 3:30 PM three electrons four electrons six electrons eight electrons Consider a hypothetical atom with an atomic number of 4 and a net charge of +1. How many neutrons does this ion have? ( Concept 2.3) one three four The answer cannot be determined from the information provided. None of the listed responses is correct. When one or more pairs of valence electrons are shared by two neutral atoms, what type of bond is formed? ( Concept 2.3) an ionic bond a hydrogen bond a covalent bond a neutral bond an electronegative bond A covalent bond is likely to be polar if __________. ( Concept 2.3) the two atoms sharing electrons are equally electronegative it is between two atoms that are both very strong electron donors one of the atoms sharing electrons is much more electronegative than the other the two atoms sharing electrons are of the same element it is between two atoms that are both very strong electron acceptors When the proton number and electron number are unequal, the atom or molecule __________. ( Concept 2.3) https://wps.pearsoncustom.com/pls_1269930281_campbell_biology_hcc/245/62942/16113201.cw/index.html Page 7 of 11 Practice Test 3/5/23, 3:30 PM becomes part of a molecule gains or loses a neutron gains or loses a proton is an ion forms a covalent bond with another atom Copper has an atomic number of 29 and a mass number of 64. What would result if an uncharged copper atom lost two electrons? ( Concept 2.3) The atomic number would remain 29, the mass number would increase to 66, and the atom would be a cation with a –2 charge. The atomic number would remain 29, the mass number would remain 64, and the atom would be a cation with a +2 charge. The atomic number of the atom would remain 29, the mass number would be reduced to 62, and the atom would be an anion. 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. The atom would have a double negative charge and be an ion. 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? ( Concept 2.3) –4 –2 –1 +1 +2 Ionic bonds form as a result of __________. ( Concept 2.3) unequal sharing of electrons between atoms attraction between ions that have opposite charges sharing of electron pairs between atoms the asymmetric distribution of electrons in constant motion https://wps.pearsoncustom.com/pls_1269930281_campbell_biology_hcc/245/62942/16113201.cw/index.html Page 8 of 11 Practice Test 3/5/23, 3:30 PM attraction between a hydrogen and other atoms that share electrons unequally A hydrogen bond __________. ( Concept 2.3) is a function of hydrophobic interactions is a strong chemical bond is one in which two hydrogen atoms bond to each other is one in which hydrogen is strongly attracted to a positively charged atom is a weak chemical bond When do hydrogen bonds occur? ( Concept 2.3) when two atoms achieve stable electron configurations by sharing electrons with each other when a molecule with partial charges contacts a molecule without partial charges when partial opposite charges on molecules come close enough to attract each other when a molecule with a low molecular weight is bonded to a molecule with a high molecular weight None of the listed responses is correct. What is the role of van der Waals interactions in biological molecules? ( Concept 2.3) Van der Waals interactions are strong bonds that play a major structural role in holding proteins together. Van der Waals interactions are important only in water. Although they are weak bonds, van der Waals interactions help to reinforce the three-dimensional shapes of large molecules. Although they are weak bonds, van der Waals interactions involve the sharing of electrons. Van der Waals interactions are too weak to be significant. Which of the following molecules has the shape of a completed tetrahedron? ( https://wps.pearsoncustom.com/pls_1269930281_campbell_biology_hcc/245/62942/16113201.cw/index.html Concept 2.3) Page 9 of 11 Practice Test 3/5/23, 3:30 PM glucose (C6H12O6) methane (CH4) oxygen gas (O2) hydrogen gas (H2) water (H2O) 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? ( Concept 2.3) the number of valence electrons the atomic numbers of the atoms involved the type of bonding in the molecule the molecule's shape the number of double bonds in the molecule Which of the following statements is true about chemical reactions? ( Concept 2.4) Only inorganic molecules can participate in chemical reactions. They represent the way matter is created and destroyed. They may have different numbers of a given atom on each side of the equation arrow. They involve the making and breaking of chemical bonds. They reach chemical equilibrium when the amounts of products and reactants are equal. Which of the following statements describes a reversible reaction that has reached chemical equilibrium? ( Concept 2.4) The concentration of the reactants is equal to the concentration of the products. The rate of the reverse reaction exceeds the rate of the forward reaction. The forward and the reverse reactions have stopped. The rate of the reverse reaction equals the rate of the forward reaction. The rate of the forward reaction exceeds the rate of the reverse reaction. https://wps.pearsoncustom.com/pls_1269930281_campbell_biology_hcc/245/62942/16113201.cw/index.html Page 10 of 11 Practice Test 3/5/23, 3:30 PM Answer choices in this exercise appear in a different order each time the page is loaded. Copyright © 1995 - 2018 Pearson Education . All rights reserved. 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