Chapter 2

Question 1

…: the distance of closest approach between two nonbonded atoms

Answer 1

van der Waals distance

Question 2

In ice, each water molecule interacts … with … other water molecules

Answer 2

tetrahedrally; four

Question 3

ice is less dense than water bc H2O … upon freezing, giving it an open structure

Answer 3

expands

Question 4

liquid water consists of rapidly fluctuating, …. (clusters) of hydrogen bonded H2O molecules

Answer 4

three dimensional networks

Question 5

the energy of association of two electric charges, q1 and q2 that are immersed in a medium of dielectric constant D and separated by the distance r, is given by Coulomb’s law:

Answer 5

U = (kq1q2)/Dr
k = 9.0 x 10^9 J*m*C^-2 (proportionality constant0

Question 6

in general, the energy of association of two charged groups (the energy required to completely separate them in the medium of interest) is less than the energy of a … but greater than the energy of a …

Answer 6

covalent bond; hydrogen bond

Question 7

the tendency of water to minimize its contacts with hydrophobic molecules is termed the

Answer 7

hydrophobic effect

Question 8

the extensive H bonding network of liquid H2O is disturbed when a nonpolar group intrudes. A nonpolar group can neither accept/donate H bonds so water molecules at the surface of the cavity cannot H bond to other molecules in their usual fashion. They then must orient themselves to form a … enclosing the cavity, decreasing … as they give up some of their rotational and translational freedom

Answer 8

hydrogen-bonded network; entropy

Question 9

the aggregation of the nonpolar groups minimizes the … of the cavity and maximizes the … of the entire system

Answer 9

surface area; entropy

Question 10

Despite the temptation to attribute some mutual attraction to a collection of nonpolar groups excluded from water, their exclusion is largely a function of the …. of the surrounding water molecules, not some “hydrophobic force”

Answer 10

entropy

Question 11

…. properties: physical properties that depend on the concentration of dissolved substance rather than on their chemical features

Answer 11

colligative

Question 12

the … of a solution is the pressure that must be applied to the solution to equalize the flow of water across the membrane in both directions

Answer 12

osmotic pressure

Question 13

during dialysis, solutes diffuse across a … from regions of higher concentration to regions of lower concentration

Answer 13

semipermeable membrane

Question 14

… is also responsible for the observation that acid base reactions are among the fastest reactions that take place in aqueous solution. this process is the spontaneous movement of H+ ions in solution

Answer 14

proton jumping

Question 15

K = …

Answer 15

([H+][A-])/[HA][H2O]

Question 16

since strong acids rapidly transfer all their protons to H2O, the strongest acid that can stably exist in aqueous solutions is … likewise, there can be no stronger base in aqueous solutions than …

Answer 16

H3O+; OH-

Question 17

the pH at the midpoint of each titration is numerically equivalent to the … of its corresponding acid; at this point [HA] = …

Answer 17

pK; [A-]

Question 18

When [HA] is approximately = [A-], the pH of the solution is relatively … to the addition of strong base/acid –> buffer

Answer 18

insensitive

Question 19

the buffering capacity of these weak acids is maximal when … it is helpful to remember that a weak acid is in its useful buffer range within … of its pK

Answer 19

pH = pK; one pH unit