Question 1

What results from an unequal sharing of electrons between atoms?

Accepted Answer

A)  a nonpolar covalent bond 
B)  a polar covalent bond 
C)  an ionic bond 
D)  a hydrogen bond 
E)  a hydrophobic interaction

Question 2

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?

Accepted Answer

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

Question 3

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

Accepted Answer

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

Question 4

-The illustration above shows a representation of formic acid. A formic acid molecule

Accepted Answer

A)  will form hydrogen bonds with water molecules. 
B)  has a tetrahedral configuration of hybrid electron orbitals for the carbon atom. 
C)  consists of largely nonpolar covalent bonds. 
D)  is held together by hydrogen bonds. 
E)  has a tetrahedral shape and will form hydrogen bonds with water molecules.

Question 5

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?

Accepted Answer

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.

Question 6

We can represent atoms by listing the number of protons, neutrons, and electrons-for example,
2p⁺; 2n⁰; 2e⁻ for helium. Which of the following represents the ¹⁸O isotope of oxygen?

Accepted Answer

A)  6p⁺, 8n⁰, 6e⁻ 
B)  8p⁺, 10n⁰, 8e⁻ 
C)  9p⁺, 9n⁰, 9e⁻ 
D)  7p⁺, 2n⁰, 9e⁻ 
E)  10p⁺, 8n⁰, 9e⁻

Question 7

-Which drawing in the figure above depicts the electron configuration of an atom capable of forming three covalent bonds with other atoms?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D 
E)  E

Question 8

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

Accepted Answer

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.

Question 9

The atomic number of chlorine is 17. The atomic number of magnesium is 12. What is the formula for magnesium chloride?

Accepted Answer

A)  MgCl 
B)  MgCl₂ 
C)  Mg₂Cl 
D)  Mg₂Cl₂ 
E)  MgCl₃

Question 10

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

Accepted Answer

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.

Question 11

-Which drawing in the figure above depicts an atom with a valence of 2?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D 
E)  E

Question 12

An atom with atomic number 12 would have what type of chemical behavior in bonding with other elements?

Accepted Answer

A)  It would form ions with a +1 charge. 
B)  It would form ions with a +2 charge. 
C)  It would form ions with a -1 charge. 
D)  It would form ions with a -2 charge. 
E)  It would form two covalent bonds with other atoms.

Question 13

In ammonium chloride salt (NH₄Cl)the anion is a single chloride ion, Cl. What is the cation of NH₄Cl?

Accepted Answer

A)  N, with a charge of +1 
B)  NH, with a charge of +1 
C)  H₃, with a charge of +1 
D)  NH₄, with a charge of +1 
E)  NH₄, with a charge of +4

Question 14

Which bond or interaction would be difficult to disrupt when compounds are put into water?

Accepted Answer

A)  covalent bond 
B)  hydrogen bond 
C)  van der Waals interaction 
D)  ionic bond 
E)  either covalent bonds or ionic bonds

Question 15

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?

Accepted Answer

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.

Question 16

What is the difference between covalent bonds and ionic bonds?

Accepted Answer

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.

Question 17

Which of the following correctly describes any reaction that has reached chemical equilibrium?

Accepted Answer

A)  The concentration of the reactants equals the concentration of the products. 
B)  The rate of the forward reaction is equal to the rate of the reverse reaction. 
C)  All of the reactants have been converted to the products of the reaction. 
D)  All of the products have been converted to the reactants of the reaction. 
E)  Both the forward and the reverse reactions have stopped with no net effect on the concentration of the reactants and the products.

Question 18

Oxygen has an atomic number of 8 and a mass number of 16. Thus, what is the atomic mass of an oxygen atom?

Accepted Answer

A)  exactly 8 grams 
B)  exactly 8 daltons 
C)  approximately 16 grams 
D)  approximately 16 daltons 
E)  24 amu (atomic mass units)

Question 19

Compared with ³¹P, the radioactive isotope ³²P has

Accepted Answer

A)  a different atomic number. 
B)  a different charge. 
C)  one more proton. 
D)  one more electron. 
E)  one more neutron.

Question 20

Which of the following pairs of atoms would be most likely to form an ionic bond?

Accepted Answer

A)   
B)   
C)   
D)   
E)

Exam 2: The Chemical Context of Life