Gen Chem II: Exam 2

Question 1

pressure is proportional to —

Answer 1

molarity

Question 2

for gases use K__

Answer 2

p

Question 3

for aq use K__

Answer 3

c

Question 4

both gases and aq use K__

Answer 4

c

Question 5

when does Kp equal Kc?

Answer 5

if the amount of gas does not change in the reaction

Question 6

what are the components present in an expression for K?

Answer 6

gaseous and aqueous

Question 7

restores balance; if a system at equilibrium is disturbed, the disturbance causes the equilibrium position to shift

Answer 7

Le Chatelier’s Principle

Question 8

which side will the reaction shift to?

Answer 8

the direction that minimizes the disturbance to achieve equilibrium again

Question 9

what factors change the equilibrium position?

Answer 9

concentration
pressure/volume
temperature

Question 10

If a chemical is removed, the system will act to produce more of it, making the reaction go to the —

Answer 10

left

Question 11

If a chemical is present in excess, the system will act to consume it, making the reaction go to the —

Answer 11

right

Question 12

only — and — will cause a shift

Answer 12

g and aq

Question 13

decreased pressure means increased — (and vice versa)

Answer 13

volume

Question 14

equilibrium shifts to the side with (more or less?) moles of gas when there is decreased pressure

Answer 14

more

Question 15

equilibrium shifts to the side with (more or less?) moles of gas when there is increased pressure

Answer 15

less

Question 16

adding an — has no effect on the equilibrium position, as long as the volume dos not change

Answer 16

inert gas

Question 17

changes in — and — have no effect on K

Answer 17

pressure and volume

Question 18

give the Arrhenius definition of acids and bases

Answer 18

acids produce H+ ions in water

bases produce OH- ions in water

Question 19

give the Bronsted-Lowry definition of acids and bases

Answer 19

acids are proton donors and bases are proton acceptors

Question 20

water is —

Answer 20

amphoteric

Question 21

can be an acid or a base

Answer 21

amphoteric

Question 22

any species that donates an electron pair to form a bond

Answer 22

a Lewis base

Question 23

any species that accepts an electron pair to form a bond

Answer 23

a Lewis acid

Question 24

molecules with incomplete octets of electrons

Answer 24

Lewis acids

Question 25

a --- acts as a Lewis acid when solvated by water

Answer 25

metal cation

Question 26

water dissociates very slightly into ions in an equilibrium process known as ---

Answer 26

autoioniaztion or self-ionization

Question 27

same number of base and acid molecules

Answer 27

neutral

Question 28

dissociates completely into ions in water

Answer 28

strong acid

Question 29

dissociates slightly to form ions in water

Answer 29

a weak acid

Question 30

a dilute solution of a strong acid contains no --- molecules

Answer 30

HA

Question 31

anions of carboxylic acids are -- stabilized

Answer 31

resonance

Question 32

the acid dissociation constant

Answer 32

Ka

Question 33

stronger acids have a (smaller or larger) Ka?

Answer 33

larger

Question 34

weaker acids have a (smaller or larger) Ka?

Answer 34

smaller

Question 35

as the [HA] decreases, the % dissociation of the acid ---

Answer 35

increases

Question 36

an acid is an acid with more than one ionizable proton

Answer 36

polyprotic acid

Question 37

--- and --- form a conjugate acid-base pair

Answer 37

Ka and Kb

Question 38

a solution that minimizes changes in pH when acids or bases are added to it

Answer 38

acid-base buffer

Question 39

what do acid-base buffers consist of?

Answer 39

appreciable quantities of conjugate acid-base pairs

Question 40

more specifically, an acid-base buffer is composed of:

Answer 40

1. acid and its conjugate base: HA & A- | 2. base and its conjugate acid: B & BH+

Question 41

a buffer woks through the ---

Answer 41

common-ion effect

Question 42

an application of Le Chatelier's principle (for buffers)

Answer 42

common-ion effect

Question 43

how does a buffer work?

Answer 43

the buffer components (HA & A-) are able to consume small amounts of added OH- or H3O+ by a shift in equilibrium position. This shift absorbs the change in [H3O+] or [OH-] and the pH changes only slightly

Question 44

since Ka is a constant, the [H3O+] of the solution depends on ---

Answer 44

the ration of buffer component concentrations

Question 45

if the ratio [HA]/[A-] increases, [H3O+] ---

Answer 45

increases

Question 46

if the ratio [HA]/[A-] decreases, [H3O+] ---

Answer 46

decreases

Question 47

the pH range over which the buffer is effective

Answer 47

the buffer range

Question 48

when are buffers most effective?

Answer 48

when the pH=pKa of the acid

Question 49

buffers have a usable range within --- of the pKa

Answer 49

+/- 1 pH unit

Question 50

the ability of the buffer solution to resist changes in pH

Answer 50

buffer capacity

Question 51

buffers with the greatest absolute concentration have the --- buffer capacity

Answer 51

largest

Question 52

when the strong base is added, the pH increases least for the ---

Answer 52

most concentrated buffer

Question 53

how do you prepare a buffer?

Answer 53

1. choose a conjugate acid with a pKa near the pH range 2. Mix the appropriate amounts of CA and CB to reach the desired pH (pH=pKa + log([CB]/[CA]) or 2. partially neutralize a weak acid or base with a strong acid or base, respectively.