BIO 101: Homework 2

b

A covalent bond is formed by a) transfer of a proton from one atom to another. b) sharing of a pair of electrons between two atoms. c) sharing of a single electron between two atoms. d) sharing of a pair of protons between two atoms. e) transfer of an electron from one atom to another.

a

A covalent chemical bond is one in which a) outer-shell electrons of two atoms are shared so as to occupy the outer electron shells of both atoms. b) an electron from a full outer electron shell of one atom is shared so as to occupy the outer electron shell of both atoms. c) outer-shell electrons of one atom are transferred to fill the inner electron shell of another atom. d) protons and neutrons are shared by two atoms so as to satisfy the requirements of both atoms. e) electrons are removed from one atom and transferred to another atom so that the two atoms become oppositely charged.

d

A substance that cannot be broken down into other substances by ordinary chemical procedures is a(n) _____. a) compound b) isotope c) proton d) element e) molecule

d

About 20-25% of the 92 natural elements are known to be essential to life. Which four of these elements make up approximately 96% of living matter? a) carbon, sodium, hydrogen, nitrogen b) carbon, oxygen, phosphorus, hydrogen c) carbon, oxygen, nitrogen, calcium d) carbon, hydrogen, nitrogen, oxygen e) oxygen, hydrogen, calcium, nitrogen

a

An acid is a substance that _____. a) increases the hydrogen ion concentration of an aqueous solution b) reduces the hydrogen ion concentration of a solution c) contains hydrogen d) forms covalent bonds with other substances e) is a versatile solvent

a

An ionic bond is formed by a) transfer of an electron from one atom to another. b) sharing of a pair of protons between two atoms. c) sharing of a single electron between two atoms. d) sharing of a pair of electrons between two atoms. e) transfer of a proton from one atom to another.

c

Because organisms are made primarily of water, they resist rapid temperature changes. This useful quality is based on water's _____. a) solvation ability b) lower density in the solid phase c) high specific heat d) cohesion e) buffering activity

b

Buffers are substances that help resist shifts in pH by a) releasing H+ to a solution when acids are added. b) accepting H+ from a solution when acids are added. c) accepting OH- to a solution when bases are added. d) accepting OH- from a solution when acids are added. e) releasing OH- to a solution when bases are added.

b

Each water molecule is joined to _____ other water molecules by ____ bonds. a) four ... polar covalent b) four ... hydrogen c) two ... polar covalent d) two ... hydrogen e) three ... ionic

a

From the atomic mass, one can deduce the number of ________ in each atom of an element. a) protons plus neutrons b) neutrons c) protons d) electrons e) protons plus electrons

c

Hydrophobic substances such as vegetable oil are a) charged molecules that hydrogen-bond with water molecules. b) polar substances that have an affinity for water. c) nonpolar substances that repel water molecules. d) nonpolar substances that have an attraction for water molecules. e) polar substances that repel water molecules.

c

If acid rain has lowered the pH of a particular lake to pH 4.0, which of the following statements about this lake is true? a) The hydrogen ion concentration is 4.0 moles per liter of lake water. b) The hydrogen ion concentration is 1 × 10-10 moles per liter of lake water. c) The hydroxyl ion concentration is 1 × 10-10 moles per liter of lake water. d) The hydroxyl ion concentration is 1 × 10-4 moles per liter of lake water. e) The hydrogen ion concentration is 1 × 104 moles per liter of lake water.

b

In a neutral solution the concentration of _____. a) water molecules is less than the concentration of hydrogen ions b) hydrogen ions is equal to the concentration of hydroxide ions c) water molecules is less than the concentration of hydroxide ions d) hydrogen ions is greater than the concentration of hydroxide ions e) hydrogen ions is less than the concentration of hydroxide ions

e

In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by a) ionic bonds. b) nonpolar covalent bonds. c) van der Waals interactions. d) hydrogen bonds. e) polar covalent bonds.

e

Many of water's emergent properties, such as its cohesion, its high specific heat, and its high heat of vaporization, result from the fact that water molecules _____. a) are extremely large b) are very small c) tend to repel each other d) are in constant motion e) are attracted to each other by partial negative and positive charges on the oxygen and hydrogen atoms, respectively

c

The atoms of different phosphorus isotopes __________. a) have different atomic numbers b) have different numbers of electrons c) have different numbers of neutrons d) have different numbers of protons e) react differently with other atoms

c

The innermost electron shell of an atom can hold up to _____ electrons. a) 18 b) 32 c) 2 d) 1 e) 8

a

The tendency of an atom to pull electrons toward itself is referred to as its _____. a) electronegativity b) polarity c) covalency d) tonicity e) ionic potential

b

The unequal sharing of electrons within a water molecule makes the water molecule _____. a) ionic b) polar c) hydrophobic d) change easily from a liquid to gaseous form e) have a low surface tension

a

Water molecules are able to form hydrogen bonds with a) compounds that have polar covalent bonds. b) oxygen gas (O2) molecules. c) compounds that have nonpolar covalent bonds. d) methane gas (CH4) molecules. e) compounds that are not soluble in water.

b

What determines the types of chemical reactions that an atom participates in? a)the number of protons it contains b) the number of electrons in the outermost electron shell c) its atomic number d) the number of electrons in the innermost electron shell e) its atomic mass

b

What results from an unequal sharing of electrons between atoms? a) an ionic bond b) a polar covalent bond c) a nonpolar covalent bond d) a hydrophobic interaction

e

Which of the following subatomic particles always has a positive charge? a) neutron b) element c) atom d) electron e) proton

a

Which of these relationships is true of an uncharged atom? a) The number of protons is equal to the number of electrons. b) The number of neutrons is equal to the number of protons. c) The number of electrons is equal to the number of neutrons. d) The atomic mass is equal to the atomic number. e) The atomic mass is equal to the number of electrons.

c

Which property of water allows a paper towel to pick up a puddle of water? a) water's high surface tension b) water's high heat of vaporization c) adhesion of water molecules to other kinds of molecules

b

Which type of bond must be broken for water to vaporize? a) both polar covalent bonds and hydrogen bonds b) hydrogen bonds c) polar covalent bonds d) both hydrogen bonds and ionic bonds e) ionic bonds

e

Why does ice float in liquid water? a) The high surface tension of liquid water keeps the ice on top. b) The ionic bonds between the molecules in ice prevent the ice from sinking. c) The crystalline lattice of ice causes it to be denser than liquid water. d) Ice always has air bubbles that keep it afloat. e) Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water.

c

a) water b) hydrogen ion c) hydroxide ion d) hydronium ion e) proton