Chem112B Exam 3 Flashcards
1
Q
7 strong acids
A
HCl, HBr, HI, HClO3, HClO4, H2SO4, HNO3
2
Q
8 strong bases
A
LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2
3
Q
Strong acids/bases dissociation rule
A
Strong electrolytes and dissociate 100%
4
Q
Group 1A and heavy 2A hydroxides are…
A
strong bases
5
Q
The conjugate base of a strong acid is a
A
negligible base
6
Q
The conjugate acid of a strong base is a
A
negligible acid
7
Q
For weaker acids and bases, the stronger the the acid, the
A
weaker its conjugate base
8
Q
Amines functional group is
A
weak base
9
Q
Carboxylic acids and thiol functional groups are
A
weak acids
10
Q
acid –>
A
H + conjugate base
11
Q
Arrhenius acid
A
Produce H+ when dissolved in water
12
Q
Arrhenius base
A
Produce OH- when dissolved in water
13
Q
Bronsted acids donate
A
H
14
Q
Bronsted bases accept
A
H
15
Q
Amphoteric
A
Can act as either acid or base (H2O)
16
Q
H + group 1A/2A metals =
A
basic in water
17
Q
H + nonmetal
A
acidic in water
18
Q
Regarding H + nonmetal, if same group…
A
larger atoms=more acidic
19
Q
Regarding H + nonmetal, if same row,
A
more electronegativity=more acidic
20
Q
Oxide + 1A/2A =
A
Basic
21
Q
Oxide + nonmetal =
A
Acidic
22
Q
Oxide + border metals/nonmetals =
A
Amphoteric
23
Q
Lewis acids
A
accept electrons
24
Q
Lewis bases
A
donate electrons and must have at least 1 lone pair
25
Lewis acids charge
+ or neutral
26
Lewis bases charge
- or neutral
27
Lewis acids common examples
Transition metals, group III and small group II cations, incomplete octets (BF3)
28
Lewis bases common examples
NH3, H20, F-, CN-
29
Group 1A and heavy group 2A oxides/hydroxides are
basic
30
Non-metal oxides/hydroxides are
acidic
31
Al 2 O3 and Al(OH) 3 are
amphoteric
32
Acidity increases as electronegativity of central atom
increases
33
For oxyacids and carboxylic acids: the more
electronegative the central atom, the higher the number
of oxygen (and other electronegative) atoms attached,
the
stronger the acid
34
Kw of 25 celcius
1 * 10^-14
35
pH=
-log(H)
36
pOH=
-log(OH)
37
(14 at 25 celcius) pKw=
pH+pOH
38
Acidic pH
less than 7 (more H than OH)
39
Basic pH
More than 7 (more OH than H)
40
For pure water, [OH −] =
H+
41
How to calculate the pH of a weak acid
1) Write acid dissociation reaction
2) Set-up ICE table to solve for [H +].
3) Solve for Ka. Weaker acids have smaller Ka (larger pKa)
42
pKa=
-log(pKa)
43
Calculate % ionization of a weak acid
% ionization = (HA ionized) / (HA initial) * 100
If in water, HA ionized = H+ equilibrium (Similar definition can be applied to %hydrolysis of a weak base)
44
calculate pH or concentrations of ions for a polyprotic acid
Set up stepwise removal of one proton at a time (multiple ICE tables)
Write Ka for each ICE table
Amphoteric species are present in the polyprotic acid
solutions
If Ka1 > Ka2 by 3 orders of magnitude or more, the pH is
determined using Ka1 only
45
Calculate pH of a weak base
Write the base hydrolysis reaction: B (aq) + H 2O () ⇌ OH − (aq) + HB + (aq)
* Weaker bases have smaller Kb (larger pKb)
* Set up ice table to solve for [OH−]
* pH=14-pOH
46
Larger Ka, smaller
pKa
47
Smaller Kb, larger
pKb
48
For conjugate acid/base pair, Kw=
Ka * Kb
49
Salts are strong electrolytes, so
they dissociate completely
50
Calculate pH of a salt solution
Dissociate salt completely to obtain the correct
concentration of ions
* Write acid dissociation of cation, or base hydrolysis reaction of anion.
* Follow steps for weak acid or weak base equilibrium to solve for pH. Use Ka x K b = Kw for a conjugate acid/base pair to find the correct Keq
51
If Ka is 10-5 or smaller, assume
negligible
52
Larger Kb means stronger
base
53
Strong acid + Strong base favors
products
54
Strong acid + Weak base favors
products
55
Weak acid + Strong base favors
products
56
Weak acid + Weak base favors
Depends on Ka
57
Larger Keq favors
products
58
For cations, conjugate acid of weak base makes
weak acid, so acidic solution
59
For cations, cations of group 1A/heavy 2A have
no pH effect
60
For cations of transition metals, group 3A, light 2A
acidic solution
61
For anions, conjugate base of strong acid have
no pH effect (HSO4- exception)
62
For anions, conjugate base of weak acid has
weak base, so basic solution
63
For anions, if has ionizable protons, it is
amphoteric, so pH effect depends on Ka and Kb (HSO4- exception, always acidic)
64
Addition of common ion decreases
ionization
65
Buffer definition
Solution that contains
* a weak acid and salt of its conjugate base
* a weak base and salt of its conjugate acid
66
Make a buffer (2 methods)
Simply combine a weak acid and salt of its conjugate
base; or a weak base and salt of its conjugate acid
Use neutralization to combine a excess weak acid
with a strong base, or a excess weak base with a
strong acid.
67
Optimal pH of a buffer =
pKa
68
More concentrated buffer solution has
greater buffer capacity
69
Use H-H equation to calculate pH of a buffer
pH = pKa + log([X-] / [HX])
* [X –] is the concentration of the conjugate base;
* [HX] is the concentration of the conjugate acid
70
How to find pH of buffer mixture after addition of small amount of strong
acid or base.
Neutralization of the added strong acid or base: write balanced reaction and make ICF table of moles
Add strong acid:
X –(aq) + H +(aq) → HX(aq)
Add strong base:
HX(aq) + OH – (aq) → X – (aq) + H 2O(l)
* Calculate concentration of HX and X – species present in the resultant solution, and use H-H equation to calculate the new pH
71
On a titration curve, initial pH indicates
strength of acid or base
72
On a titration curve, Equivalence point is when
stoichiometrically equivalent quantities of acid and base reacted (straight up/down)
73
On a titration curve, Buffer mixture are produced between
initial and equivalence point
74
On a titration curve, At half equivalence point pH=
= pKa
75
Describe a polytropic titration curve
Polyprotic has multiple equivalence points, and multiple
buffer regions
76
How to choose appropriate indicator
Indicator must change color within the vertical range of pH change
77
How to find pH of acid/base mixture at any point during a titration
* Make ICF table of moles for neutralization,
* Calculate moles and concentration of species present in
the final solution,
* Identify whether the final solution is a buffer mixture, has
a weak base or a weak acid only, or has excess strong acid
or base, and find pH accordingly.
