Chpt 16: Acid Base Chemical Equilibria

Question 1

How should you find the pH if you’re mixing 2 different weak acids, where one acid is way weaker than the other?

Answer 1

Do the ICE table for the stronger of the two weak acids.

the weaker acid’s [H+] won’t contribute much to the overall pH

Question 2

Why does conjugate resonance impact the strength of carboxylic acids?

Answer 2

if the conjugate (which an an anion) is stable 2o to its resonance, it is not likely to reclaim H+ to become an acid

Question 3

what does pH + pOH equal?

Answer 3

14

Question 4

One of the types of weak bases is neutral structures with unpaired e-. What are the two kinds of neutral structures with unpaired e-?

Answer 4

NH3 and amines

Question 5

what is the expression for “Ka” ?

Answer 5

[H+][A-]/[HA]

Question 6

what does Kw equal at room temperature?

Answer 6

1.0E-14

Question 7

what does [H+][OH-] equal?

Answer 7

1.0E-14

Question 8

how does bond strength generally impact the strength of an acid/base

Answer 8

stronger bond, weaker acid/base

Question 9

True or false: when comparing the strength of weak bases, the more negative the base’s charge, the more attractive it is to H+

Answer 9

True; More negative, more ability to accept H+

exp. HCO3^- is a weaker base than CO3^2-

Question 10

what are salts?

Answer 10

ionic compounds that make ions in solution

Question 11

what is an amine?

Answer 11

type of weak bases:

characterized as a neutral substance with a nitrogen that has an unbound electron pair for accepting H+

Question 12

how does conjugate stability generally impact the strength of an acid or base?

Answer 12

the more stable the conjugate, the more stronger the acid/base?

Question 13

How do oxyacids’ strength trend as more terminal oxygens are added?

Answer 13

more terminal oxygens, stronger acid (because polarity goes up as oxygens are added)

Question 14

true or false: if an acid/base is a Lewis acid/base, it must also be a BL acid/based and a Arrhenius acid/base

Answer 14

false. (because Lewis acids/bases’ definition does not depend upon H+ involvement like the BL and Arrhenius definitions do)

Lewis is the most general of all the definitions

Question 15

true or false: in the case of oxyacids, the more terminal oxygens around central atom, the stronger the acid?

Answer 15

true

Question 16

what would happen if you forgot the - sign while trying to go from pH to [H+] using your elementary school calculator

Answer 16

it would give you the wrong answer

Question 17

what is an oxyacid?

Answer 17

A molecule in which a central atom is surrounded by terminal atoms (sometimes terminal oxygens), including an OH- group or groups

Question 18

how does atomic radii generally impact bond strength?

Answer 18

bigger radii, weaker bond

Question 19

If you’re mixing a weak acid and a weak base, how can you tell whether the pH will be acidic or basic?

Answer 19

The component with the larger Keq will be the one that determines the pH

Exp.if Ka is bigger than kb, the solution will be acidic

Question 20

what is the expression for “Kw” (in terms of ka and kb)?

Answer 20

ka * kb = kw

Question 21

what does the “Kw” k constant represent?

Answer 21

the autoionization of water

Question 22

how are Lewis acids defined?

Answer 22

as electron pair acceptors

Question 23

what are binary acids?

Answer 23

acids that only have two kinds of atoms in them

Question 24

how are Lewis bases defined?

Answer 24

as electron donors

Question 25

true or false: the stronger the acid, the weaker the base

Answer 25

true

Question 26

what does the "Ka" k constant represent?

Answer 26

ratio of ions to acid molecules

Question 27

when do you have to bother with ICE tables: with strong acids/bases or weak acids/bases?

Answer 27

waek

Question 28

how do you go from [H+] to pH?

Answer 28

take the -log of [H+]

Question 29

what are the two types of weak bases?

Answer 29

neutral structures (that have unpaired e- for accepting H+) charged structures (that are conjugates of weak acids)

Question 30

true or false: if an acid/base is a BL acid/based or a Arrhenius acid/base, it must also be a Lewis acid/base

Answer 30

true

Question 31

in a chemical reaction, how can you tell which component acts as a Lewis BASE

Answer 31

it will give its unpaired electrons to something else exp. if Fe(ClO4)3 + 6H2O makes Fe(H2O)6 + 3ClO4^1, H2O gave its unpaired electrons to Fe^3+, and is thus acting as a base

Question 32

how does bond strength trend on the periodic table?

Answer 32

strength goes up as you go up the periodic table

Question 33

in a chemical reaction, how can you tell which component acts as a Lewis acid

Answer 33

it will accept/receive something else's electron pair exp. if Fe(ClO4)3 + 6H2O makes Fe(H2O)6 + 3ClO4^1, the Fe receives the unpaired electrons that H2O had, and is thus acting as an acid

Question 34

in ka or kb problems, when can you ignore the x in the denominator?

Answer 34

when the acid or base concentration decreases by less than 5% in order to achieve equilibrium and/or when your final acid or base concentration is 5% or less of the original concentration

Question 35

When comparing weak acid or base strength, what can you consider in addition to polarity, bond strength, and stability of the acid's/base's conjugate?

Answer 35

the ka or kb values involved

Question 36

what does a large ka mean?

Answer 36

large ionization; strong acid

Question 37

how does binary acid strength trend as you go across the periodic table?

Answer 37

acid gets stronger as you go to the right (bc polarity increases)

Question 38

what is the expression for "Kw" (in terms of H+ and OH- concentrations)?

Answer 38

kw = [H+][OH-]

Question 39

how do you go from pH to [H+] using your elementary school calculator?

Answer 39

2nd, LOG, -, [pH] you have to remember the - sign!!!

Question 40

true or false: in the case of oxyacids, the more electronegative the central atom, the stronger the acid?

Answer 40

true

Question 41

How do oxyacids' strength trend as the OXIDATION NUMBER of their central atom increases?

Answer 41

higher the oxi number, stronger the acid

Question 42

How do oxyacids' strength trend as the electronegativity of their central atom increases?

Answer 42

acid gets stronger as electronegativity of the central atom goes up

Question 43

How should you find the pH if you’re mixing 2 different weak acids, where both acids are equally weak?

Answer 43

Do the ICE table for both, find the [H+] for both, add the two [H+] values together, and use that to calculate the pH

Question 44

how does binary acid strength trend as you go up the periodic table?

Answer 44

acid gets stronger as you go down the table (bc bond strength gets weaker as radius increases)

Question 45

how does polarity generally impact the strength of an acid or base?

Answer 45

bigger dipole, strong acid/base