Archive for December 2016

Van der Waals interactions result when

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Van der Waals interactions result when 





A) hybrid orbitals overlap.
B) electrons are not symmetrically distributed in a molecule.
C) molecules held by ionic bonds react with water.
D) two polar covalent bonds react.
E) a hydrogen atom loses an electron.







Answer: B

What is the difference between covalent bonds and ionic bonds?

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What is the difference between covalent bonds and ionic bonds? 







A) Covalent bonds are formed between atoms to form molecules; ionic bonds are formed between atoms to form compounds.
B) Covalent bonds involve the sharing of pairs of electrons between atoms; ionic bonds involve the sharing of single electrons between atoms.
C) Covalent bonds involve the sharing of electrons between atoms; ionic bonds involve the electrical attraction between atoms.
D) Covalent bonds involve the sharing of electrons between atoms; ionic bonds involve the sharing of protons between atoms.
E) Covalent bonds involve the transfer of electrons between atoms; ionic bonds involve the sharing of electrons between atoms.







Answer: C

In comparing covalent bonds and ionic bonds, which of the following would you expect?

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In comparing covalent bonds and ionic bonds, which of the following would you expect? 






A) An atom can form covalent bonds with multiple partner atoms, but only a single ionic bond with a single partner atom.
B) Covalent bonds and ionic bonds occupy opposite ends of a continuous spectrum, from nearly equal to completely unequal sharing of electrons.
C) Both involve electrical attraction between the electrons of one atom and the nucleus of the other atom.
D) Ionic interactions remain when covalent bonds are broken in water. Ionic bonds are much stronger than covalent bonds.





Answer: B

A covalent bond is likely to be polar when

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A covalent bond is likely to be polar when 






A) one of the atoms sharing electrons is much more electronegative than the other atom.
B) the two atoms sharing electrons are equally electronegative.
C) oxygen is one of the two atoms sharing electrons.
D) one of the atoms has absorbed more energy than the other atom.
E) the two atoms sharing electrons are different elements.






Answer: A

Nitrogen (N) is much more electronegative than hydrogen (H). Which of the following statements is correct about the atoms in ammonia (NH3)?

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Nitrogen (N) is much more electronegative than hydrogen (H). Which of the following statements is correct about the atoms in ammonia (NH3)? 







A) Each hydrogen atom has a partial positive charge; the nitrogen atom has a partial negative charge.
B) The nitrogen atom has a strong positive charge; each hydrogen atom has a strong positive charge.
C) Each hydrogen atom has a slight negative charge; the nitrogen atom has a strong positive charge.
D) The nitrogen atom has a slight positive charge; each hydrogen atom has a slight negative charge.
E) There are covalent bonds between the hydrogen atoms and polar bonds between each hydrogen atom and the nitrogen atom.







Answer: A

A covalent chemical bond is one in which

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A covalent chemical bond is one in which 






A) electrons are removed from one atom and transferred to another atom so that the two atoms become oppositely charged.
B) protons and neutrons are shared by two atoms so as to satisfy the requirements of both atoms.
C) outer-shell electrons of two atoms are shared so as to satisfactorily fill the outer electron shells of both atoms.
D) outer-shell electrons of one atom are transferred to fill the inner electron shell of another atom.
E) an electron occupies a hybrid orbital located between the nuclei of two atoms.







Answer: C

If a salamander relied on hydrogen bonds to cling to surfaces, what type of surface would cause the most problems for this animal?

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If a salamander relied on hydrogen bonds to cling to surfaces, what type of surface would cause the most problems for this animal? 





A) a surface coated with a thin film of water
B) a surface made with carbon and hydrogen atoms covalently bonded together
C) a surface made with carbon, hydrogen, and oxygen atoms covalently bonded together
D) a surface made with carbon, hydrogen, nitrogen, and oxygen atoms covalently bonded together
E) a surface made with silicon and oxygen atoms covalently bonded together








Answer: B

Phosphorus-32, a radioactive isotope of phosphorus-31 (atomic number 15), undergoes a form of radioactive decay whereby a neutron turns into a proton and emits radiation in the form of an electron. What is the product of such radioactive decay of phosphorus-32?

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Phosphorus-32, a radioactive isotope of phosphorus-31 (atomic number 15), undergoes a form of radioactive decay whereby a neutron turns into a proton and emits radiation in the form of an electron. What is the product of such radioactive decay of phosphorus-32? 





A) phosphorus-31
B) a positively charged phosphorus-31 ion
C) a negatively charged phosphorus-32 ion
D) sulfur-32 (atomic number 16)
E) the conversion of the phosphorus-32 atom into pure energy







Answer: D

The organic molecules in living organisms have a measurably lower ratio of carbon-13/carbon-12, two stable isotopes of carbon that comprise approximately 1.1% and 98.9% of atmospheric carbon, respectively. What is a reasonable explanation for this phenomenon?

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The organic molecules in living organisms have a measurably lower ratio of carbon-13/carbon-12, two stable isotopes of carbon that comprise approximately 1.1% and 98.9% of atmospheric carbon, respectively. What is a reasonable explanation for this phenomenon? 




A) Photosynthesis preferentially uses carbon dioxide molecules with carbon-12, and the lower carbon-13/carbon-12 ratio propagates through the food chain.
B) Carbon dioxide molecules with carbon-13 stay in the upper atmosphere and are less available to terrestrial plants and algae.
C) Carbon-13 has a different valence electron configuration and is therefore less chemically reactive than carbon-12.
D) Oxygen atoms preferentially react with carbon-13, thereby enriching the atmosphere with carbon dioxide molecules containing carbon-13 atoms.
E) Carbon dioxide molecules containing carbon-13 are heavier and sink into the ocean depths, making them less available to living organisms.







Answer: A

Two atoms appear to have the same mass number. These atoms

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Two atoms appear to have the same mass number. These atoms 





A) must have the same atomic number.
B) must have the same number of electrons.
C) must have the same chemical properties.
D) must have the same number of protons + neutrons.
E) must have the same atomic number, the same number of protons + neutrons, the same number of electrons, and the same chemical properties.






Answer: D

Atoms whose outer electron shells contain 8 electrons tend to

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Atoms whose outer electron shells contain 8 electrons tend to 





A) form ions in aqueous solutions.
B) form hydrogen bonds in aqueous solutions.
C) be stable and chemically nonreactive, or inert.
D) be gaseous at room temperature.
E) be both chemically inert and gaseous at room temperature.






Answer: E

The atomic number of neon is 10. Therefore, which of the following is most correct about an atom of neon?

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The atomic number of neon is 10. Therefore, which of the following is most correct about an atom of neon? 




A) It has 8 electrons in its outer electron shell.
B) It is inert.
C) It has an atomic mass of 10 daltons.
D) It has 8 electrons in its outer electron shell and it is inert.
E) It has 8 electrons in its outer electron shell, it is inert, and it has an atomic mass of 10 daltons.







Answer: D

Electrons exist only at fixed levels of potential energy. However, if an atom absorbs sufficient energy, a possible result is that

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Electrons exist only at fixed levels of potential energy. However, if an atom absorbs sufficient energy, a possible result is that 







A) an electron may move to an electron shell farther away from the nucleus.
B) an electron may move to an electron shell closer to the nucleus.
C) the atom may become a radioactive isotope.
D) the atom would become a positively charged ion, or cation, and become a radioactive isotope.
E) the atom would become a negatively charged ion, or anion.



Answer: A

One difference between carbon-12 (12/6 C) is that carbon-14 (14/6 C) has

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One difference between carbon-12 (12/6 C) is that carbon-14 (14/6 C) has 





A) two more protons than carbon-12.
B) two more electrons than carbon-12.
C) two more neutrons than carbon-12.
D) two more protons and two more neutrons than carbon-12.
E) two more electrons and two more neutrons than carbon-12.






Answer: C

The precise weight of a mole of some pure elements like silicon (Si) can vary slightly from the standard atomic mass, or even from sample to sample. Why?

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The precise weight of a mole of some pure elements like silicon (Si) can vary slightly from the standard atomic mass, or even from sample to sample. Why? 





A) The element may undergo radioactive decay.
B) The element may react with itself and gain or lose subatomic particles.
C) The atoms of the element form chemical bonds with each other, and that changes the weight of the element.
D) The element may have multiple stable isotopes, and the isotopic composition may vary from sample to sample.
E) The amount of energy absorbed by the element affects the mass of its electrons, and thus the atomic mass can vary slightly.






Answer: D

Carbon-12 is the most common isotope of carbon, and has an atomic mass of 12 daltons. A mole of carbon in naturally occurring coal, however, weighs slightly more than 12 grams. Why?

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Carbon-12 is the most common isotope of carbon, and has an atomic mass of 12 daltons. A mole of carbon in naturally occurring coal, however, weighs slightly more than 12 grams. Why? 






A) The atomic mass does not include the mass of electrons.
B) Some carbon atoms in nature have an extra proton.
C) Some carbon atoms in nature have more neutrons.
D) Some carbon atoms in nature have a different valence electron distribution.
E) Some carbon atoms in nature have undergone radioactive decay.






Answer: C

Molybdenum has an atomic number of 42. Several common isotopes exist, with mass numbers of 92, 94, 95, 96, 97, 98, and 100. Therefore, which of the following can be true?

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Molybdenum has an atomic number of 42. Several common isotopes exist, with mass numbers of 92, 94, 95, 96, 97, 98, and 100. Therefore, which of the following can be true? 






A) Molybdenum atoms can have between 50 and 58 neutrons.
B) The isotopes of molybdenum have different electron configurations.
C) The isotopes of molybdenum can have between 50 and 58 protons.
D) The isotopes of molybdenum have between 50 and 58 neutrons and have different electron configurations.
E) The isotopes of molybdenum have between 50 and 58 protons and have different electron configurations.






Answer: A

The nucleus of a nitrogen atom contains 7 neutrons and 7 protons. Which of the following is a correct statement concerning nitrogen?

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The nucleus of a nitrogen atom contains 7 neutrons and 7 protons. Which of the following is a correct statement concerning nitrogen? 





A) The nitrogen atom has a mass number of approximately 7 daltons and an atomic mass of 14.
B) The nitrogen atom has a mass number of approximately 14 daltons and an atomic mass of 7.
C) The nitrogen atom has a mass number of 14 and an atomic mass of 7 grams.
D) The nitrogen atom has a mass number of 7 and an atomic number of 14.
E) The nitrogen atom has a mass number of 14 and an atomic mass of approximately 14 daltons.





Answer: E

In what way are elements in the same column of the periodic table the same?

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In what way are elements in the same column of the periodic table the same? 





A) They have the same number of protons.
B) They have the same number of neutrons.
C) They have the same number of electrons.
D) They have the same number of electrons in their valence shell.
E) They have the same number of electron shells.





Answer: D

Knowing just the atomic mass of an element allows inferences about which of the following?

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Knowing just the atomic mass of an element allows inferences about which of the following? 





A) the chemical properties of the element
B) the number of protons in the element
C) the number of neutrons in the element
D) the number of protons plus neutrons in the element
E) both the number of protons and the chemical properties of the element






Answer: D

Why is each element unique and different from other elements in chemical properties?

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Why is each element unique and different from other elements in chemical properties? 






A) Each element has a unique atomic mass.
B) Each element has a unique atomic weight.
C) Each element has a unique number of protons in its nucleus.
D) Each element has a unique number of neutrons in its nucleus.
E) Each element has different radioactive properties.







Answer: C

What factors are most important in determining which elements are most common in living matter?

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What factors are most important in determining which elements are most common in living matter? 





A) the relative abundances of the elements in Earth's crust and atmosphere
B) the emergent properties of the simple compounds made from these elements
C) the reactivity of the elements with water
D) the chemical stability of the elements
E) both the relative abundances of the elements and the emergent properties of the compounds made from these elements





Answer: E

Which of the following statements is false?

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Which of the following statements is false? 





A) Carbon, hydrogen, oxygen, and nitrogen are the most abundant elements of living matter.
B) Some trace elements are very abundant on Earth.
C) Virtually all organisms require the same elements in the same quantities.
D) Iron is an example of an element needed by all organisms.
E) Other than some trace elements, animals are mostly made up of the same elements as plants, in similar proportions.







Answer: C

Trace elements are those required by an organism in only minute quantities. Which of the following is a trace element that is required by humans and other vertebrates, but not by other organisms such as bacteria or plants?

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Trace elements are those required by an organism in only minute quantities. Which of the following is a trace element that is required by humans and other vertebrates, but not by other organisms such as bacteria or plants? 





A) nitrogen
B) calcium
C) iodine
D) sodium
E) phosphorus





Answer: C

About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of living matter?

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About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of living matter? 







A) carbon, sodium, hydrogen, nitrogen
B) carbon, oxygen, phosphorus, hydrogen
C) oxygen, hydrogen, calcium, nitrogen
D) carbon, hydrogen, nitrogen, oxygen
E) carbon, oxygen, nitrogen, calcium






Answer: D

Which of the following best describes the logic of scientific inquiry?

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Which of the following best describes the logic of scientific inquiry? 







A) If I generate a testable hypothesis, tests and observations will support it.
B) If my prediction is correct, it will lead to a testable hypothesis.
C) If my observations are accurate, they will support my hypothesis.
D) If my hypothesis is correct, I can expect certain test results.
E) If my experiments are set up right, they will lead to a testable hypothesis.






Answer: D

Which of the following is an example of qualitative data?

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Which of the following is an example of qualitative data? 







A) The temperature decreased from 20°C to 15°C.
B) The plant's height is 25 centimeters (cm).
C) The fish swam in a zigzag motion.
D) The six pairs of robins hatched an average of three chicks.
E) The contents of the stomach are mixed every 20 seconds.








Answer: C

Which of the following statements best distinguishes hypotheses from theories in science?

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Which of the following statements best distinguishes hypotheses from theories in science?





A) Theories are hypotheses that have been proved.
B) Hypotheses are guesses; theories are correct answers.
C) Hypotheses usually are relatively narrow in scope; theories have broad explanatory power.
D) Hypotheses and theories are essentially the same thing.
E) Theories are proved true; hypotheses are often falsified.





Answer: C

A controlled experiment is one that

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A controlled experiment is one that 







A) proceeds slowly enough that a scientist can make careful records of the results.
B) tests experimental and control groups in parallel.
C) is repeated many times to make sure the results are accurate.
D) keeps all variables constant.
E) is supervised by an experienced scientist.






Answer: B

Protists and bacteria are grouped into different domains because

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Protists and bacteria are grouped into different domains because 





A) protists eat bacteria.
B) bacteria are not made of cells.
C) protists have a membrane-bounded nucleus, which bacterial cells lack.
D) bacteria decompose protists.
E) protists are photosynthetic.








Answer: C

Systems biology is mainly an attempt to

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Systems biology is mainly an attempt to 






A) analyze genomes from different species.
B) simplify complex problems by reducing the system into smaller, less complex units.
C) understand the behavior of entire biological systems.
D) build high-throughput machines for the rapid acquisition of biological data.
E) speed up the technological application of scientific knowledge.






Answer: C

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