220 Chapter 15
CHEMISTRY 1220 EXAM #1 USEFUL INFORMATION •
We can write an expression for the relationship between the concentration of the reactan
products at equilibrium.
• This expression is based on the law of mass action.
• For a general reaction,
aA + bB
dD + eE
CONVERSIONS AND CONSTANTS 3 = 1 mL • = 1
The
is , given
1 inch= 2.54 cm, 1 nm 0-­‐9 equilibrium-constant
m, 1 pm = 10-­‐12 m, 1expression
Å = 10-­‐10 m
1 cmby:
220 Chapter 15
N = kg-­‐m/s2, Pa = N/m2, J = kg-­‐m2/s2 [Dd ][E]e
K c kPa=14.696 a theb reactants
• 760 Wemcan
write an expression
for the relationship
between the
concentration
mHg=760 torr=1 atm=1.01325 bar=101,325 Pa=101.325 psi and
[A]of
[B]
products at equilibrium.
Molar isVolume STP 22.4 L, action.
T(K) = T(°C) + 273.15 • This expression
based onat the
law= of
mass
•
Where Kc is the equilibrium constant.
• For
a general
reaction,
The speed of light is c =• 3.00 108 m/s, Planck’s = 6.626 x 10-­‐34
J sused
Thexsubscript
“c”
indicatesconstant, that molarhconcentrations
were
to evaluate the cons
aA + bB
•
dD + eE
the equilibrium
constant
expression
has products in the numerator and reac
NA = 6.022x10• 23, Note
R =expression
0that
.08206 L-­‐atm/mol-­‐K = 8.314 J/mol-­‐K The equilibrium-constant
is
given by:
denominator.
d = m/V, density of H2O at 25ºC = 1.00 g/cm3, density of Hg at 20ºC = 13.55 g/cm3 Evaluating Kc
[Dd ][E]e
c
• The value of KcKdoes
not adepend
[A]
[B]b on initial concentrations of products or reactants.
FORMULAS • Consider the reaction:
Energy states of the hydrogen atom: E = (-­‐2.18 x10-­‐18 J)(1/n2) N2O4(g)
2NO2(g)
• Where Kc is the equilibrium constant.
λ equilibrium
=molar
h/mv, Econstant
= hc/λ is given
• The
by: toChemical
• The subscript “c” indicates
that
concentrations
were used
evaluate
the constant.
Kinetics
201
Chemical E
2 and reactants in the
•
Note
that
the
equilibrium
constant
expression
has
products
in
the
numerator
]
ΔH˚rxn = Σ ΔH˚products -­‐ Σ nΔH˚reactants, ΔH˚rxn = Σ bonds broken -­‐ Σ[NO
bonds f
ormed 2
Kc
denominator.
• ass It isxthe
rate at that
particular
instant
intwo time.interacting charges E[N
]1Qpartial
q = m
specific heat x
Δ
T
P
E o
f = k2O
(Q4(or
,
2)/d pressures) for all species
•we will
Tabulate
initial
and equilibrium
concentrations
• K
For
our
discussion
call
the
"instantaneous
rate"
the
rate,
unless
otherwise
Evaluating
c
•
The
value
of
this
constant
(at
100
°C)
is
6.50
(regardless
of the initial concentrations
188 Chapter 13
F or
=equilibrium.
NO
mon
a, 2(g).
P = F/A, KE = ½ mvof2 products or reactants.
• The valueindicated.
of Kc does not depend
initial
concentrations
• 8If an initial and an equilibrium concentration are given for a species, calculate the c
2 ⎞
Reaction
Rates ⎛and
• Consider
theStoichiometry
expression depends on stoichiometry.
nreaction:
a• The equilibrium
concentration.
, a
nd for an the
ideal gases: PV = nRT P
+
V
−
nb
=
nRT
(
)
⎜
⎟
For Chapter
thepressure
reaction:
•
It
does
not
depend
mechanism.
• The amount •of 188
vapor
lowering
depends
on
the
amount
2
13
N2O4(g) ofonsolute.
2NO
2(g)
• Use the coefficients
in
thereaction
balanced
chemical equation to calculate the changes in c
V C⎠4H9Cl(aq)
⎝
+ Hvalue
CK4lowers
Hvaries
+vapor
HCl(aq)
2O(l)
9OH(aq)
The
of
with
temperature.
• Raoult’s law quantifies
to which
a •nonvolatile
solute
the
pressure
of the
c
• the
Theextent
equilibrium
constant
is
given
by:
of all
species.
H
OH
must
equal
the
rate
of
disappearance
of
C
H
•
The
rate
of
appearance
of
C
4
9
4
9Cl.
3RT
• We
generally
omit
the units 2of
the equilibrium
solvent.
Deducelowering
the
equilibrium
ofofconstant.
all
species.
Hw
here v[NO
i4s r9OH
ms son
peed v• =pressure
] concentrations
•
The
amount
of
vapor
depends
the
amount
solute.
2
C
4
9
Cl
C
H
• If Psolution is the vapor pressure of the solution,
P
°solvent
is the
vaporinpressure
ofofthe
pureequilibrium
solvent,
K ccalculate
M
Rate
•
Use
these
to
the
value
of
the
constant.
Equilibrium
Constants
Terms
Pressure,
K
p vapor
Raoult’s
quantifies
to
a nonvolatile
solute lowers the
pressure of the
t which[N
t 4]
fractionlaw
of solute,
thenthe extent
and solute is the• mole
2O
FORWARD
REFERENCES
2
2
2
•
When
the
reactants
and
products
are
gases,
we
can
write
an
equilibrium
expression using
solvent.
z
=
x
+
y
(
diagonal o
f r
ight a
ngle t
riangle), V
=
l
·
w
·
h
• What
if
the
stoichiometric
relationships
are
not
one-to-one?
box
o is 6.50 (regardless of the initial concentrations
• The value of this P
constant •(at
100
°C)
of N2O4(g)
Methods
of
finding
equilibrium
constants
from thermodynamic
or electrochemi
X
P
solution
solvent
solvent
• •For
the
reaction:
pressures
rather
than
molar
concentrations.
If
P
is
the
vapor
pressure
of
the
solution,
P
°
is
the
vapor
pressure
of
the
pure
solvent,
solvent
or NO2solution
(g).
S
=
k
P
, P
=
X
P˚
, Δ
T
=
K
m, Δ
Tf =
K
m, Π
= (
n/V)RT g
H
g
A
A
A
b
f
f
discussed
in
Chapters
19
and
20,
respectively.
.
• The vapor-pressure lowering,
P,isisthe
directly
the+then
mole
fraction
thestands
solute,forsolute
2HI(g)of solute,
Hto
I2(g)is K
2(g)
whereof“p”
pressure.
• mole
Theproportional
equilibrium
constant
fraction
and solute
• • TheThe
equilibrium
expression
15 as:depends on stoichiometry. p
rate220
mayChapter
be expressed
o
o
•
For
the
reaction:
• It does not depend15.6
on
reaction mechanism.
Pof
X solvent PsolventConstants
P the
XApplications
solution
solute Psolvent
Equilibrium
+ bB
dD + eE
0 Chapter 15
1 temperature.
HI P, is
H 2directly
I2 proportionalaA
• • The
value
of
K
varies
with
c
The
vapor-pressure
lowering,
to the mole fraction of the solute, solute.
Rate
Raoult’s
law.
• An ideal solution is one that obeys
• We
write
for
between the concentration
of the reactants and
t
t the
trelationship
• We generally
omitcan
thePredicting
unitsan
of 2expression
the the
equilibrium
constant.
Direction
of Reaction
o
(PD ) d (PE ) e
• Real solutions show approximately
idealatbehavior
when:
products
equilibrium.
P X solute Psolvent
Kand
For
aageneral
reaction:
p
We can•write
expression
forcan
thegeneralize
relationship
between
the
of
reactants
Equilibrium
Constants
in
Terms
ofconcentration
Pressure,
theansolute
concentration
is•low.This
p the
• We
this• expression
equation
bit.
is
based
on theKlaw
of mass
action.
(PA ) a (PB ) b
ideal
solution
is
one
that
obeys
Raoult’s
law.
•
An
dD + eE
aA
+
bB
products• at the
equilibrium.
solute
solvent
have
sized
molecules.
• For
reaction:
• similarly
For
a general
reaction,
the the
reactants
and
products
are
we can write
anthe
equilibrium
expression
using
• andWhen
•show
They
can
begases,
interconverted
using
ideal
gas equation
and
our partial
definition of molarity:
•
Real
solutions
approximately
ideal
behavior
when:
•
We
define
Q,
the
reaction
quotient,
as:
• This• expression
is
based
on
the
law
of
mass
action.
aA
+
bB
cC
+
dD
the solute andpressures
solvent have
types
intermolecular
attractions.
rathersimilar
than
molar
For the concentrations.
gofeneral equation: aA + bB
PV = dD
nRT+ eE
thus P = (n/V)RT
• when
the may
solute
concentration
is
low.
The
rate
besolvent-solvent
expressed
as:where
• •ForRaoult’s
a generallaw
reaction,
the
and
solute-solute
intermolecular
forcesisare
•
The
equilibrium-constant
expression
is
given
by:(n/V)
d
e
“p”
stands
for
pressure.
•breaks
The• down
equilibrium
constant
is
K
p express volume in liters the quantity
•
If
we
to molarity.
• thesolute-solvent
solute
and solvent
have
similarly
sized1 molecules.
E
D equivalent
aA
+ bB
dD
+ eE
much greater• or weaker
intermolecular
forces.
1
1
1
A
B
C
D
For the than
reaction:
Q
•
Thus
the
partial
pressure
of
a
substance,
A,
is
given
as:
Rate
a
b
the solute
solvent
similar types of intermolecular
attractions.
d
• The equilibrium-constant•expression
is and
given
by:t have
b aA
t + bB
c t dD
d + teE [DP
B [A]RT
][E]e A =
Boiling-Point Elevation46,47,48
A =(nA/V)RT intermolecular
law breaksadown
• Raoult’s
when the solvent-solvent
and
solute-solute
forces are
Kc
a
b
•of acan
Where
[A],to
[B],
[D],intermolecular
[E]
molarities
(for substances
in solution) or partial pr
• weaker
usesolute-solvent
this
obtain
a
general
expression
relating
K
and
K
dand
e are
dWe
esolution.
[A]
[B]
c
p:
or
than
forces.
greater
• A nonvolatile solute lowersmuch
the vapor
pressure
9,10,11
(PDtime.
) (PE )
][E]Laws
n
14.3 Concentration
and[DRate
gases) athas
any
Kpthan
= K1c(RT)
Kap given
K cliquid,
46,47,48
• At the normal boiling
point
of
the
pure
the
solution
has
a
vapor
pressure
less
atm.
a
b
a
b
Boiling-Point
(P
(P
[A]•K•c[B]
We
can
QAof
KBc1)oratm
Qproducts)
to K
In general,
rates:• Elevation
ncompare
= (moles
– (moles of gaseous reactants).
c )togaseous
pfor
p: solution
the equilibrium
constant.
• Therefore, a •higher
temperature
is Where
required
toisWhere
reach
a vapor
pressure
of
the
•
increase
when
reactant
concentration
is
increased.
•
A
nonvolatile
solute
lowers
the
vapor
pressure
of
a
solution.
•
If
Q
=
K,
then
the
system
is
at
equilibrium.
•
The
numerical
values
of
K
and
K
will
differ
if used
n = to
0. evaluate the constant.
•
They
can
be
interconverted
using
the
ideal
gas
equation
and
our
definition
of
molarity:
c
p
•
The
subscript
“c”
indicates
that
molar
concentrations
were
( Tb).
the
• At
decrease
as
concentration
of•of
reactants
isnRT
reduced.
•
the
normal
boiling
point
the
pure
liquid,
solution
has
a
has
a
vapor
pressure
less
than
atm.
•
Where
K
constant.
If
Q
<
K,
then
the
forward
reaction
must
occur
to
reach
equilibrium.
PV
=
thus
P
=
(n/V)RT
c is the equilibrium
•
Note
that
the
equilibrium
constant
expression
has
products
in
the
and1reactants
in the
• The molal boiling-point-elevation
constant
, Kconcentration
how
muchrateTby
with
molality,
m: numerator
b, expresses on
b changes
• indicates
examine
theaconcentrations
effect
reaction
measuring
thepressure
way
in which
•often
Therefore,
higher
temperature
is K,
required
to
reach
aconstant.
vapor
of 1 reaction
atm
for the
solution
• The subscript “c”
that
molar
were
used
to
evaluate
the
•
If
Q
>
then
the
reverse
reaction
must
occur
to
reach
equilibrium.
• We
If we
express
volume
in of
liters
the
quantity
(n/V)
is
equivalent
to
molarity.
denominator.
Tb =depends
Kbm on starting conditions.
rate at the beginning of a reaction
). expression
(theTpartial
• Note that the equilibrium
constant
hasa substance,
products
inA,
theisnumerator
in are
the
•willProducts
arecolligative
consumed,
reactants
Thus
the
pressure
of
given
as: and reactants
breaction:
Consider
• The nature of the•• solute
(electrolyte
vs.
nonelectrolyte)
impact
the
molality
of theformed.
Evaluating
Kc +
–Q
denominator.
• The molal
boiling-point-elevation
constant
,
K
,
expresses
how
much
Tb changes
withInc.
molality, m:
P
=(n
/V)RT
=
[A]RT
•
decreases
until
it
equals
K.
© 2012 Pearson
Education,
(aq) AN2(g) b+ 2HCopyright
NH4 (aq) + NO2 A
2O(l)
solute.
•
The
value
of
K
does
not
depend
on
initial
concentrations
of
products
or
reactants.
T
=
K
m
c
•
We
can
use
this
to
obtain
a
general
expression
relating
K
and
K
b
b c
• We 49,50,51
measure initial reaction rates.
p:
valuating
Kc
Calculating
Equilibrium
Concentrations
n
•ofrate
Consider
the reaction:
Freezing-Point
Depression
• The
nature
the
(electrolyte
vs.atK
nonelectrolyte)
will impact the colligative molality of the
• The
initial
issolute
the instantaneous
rate
time
0.
p = tK=c(RT)
The value of Kc does not
initial
concentrations
ofproducts)
products
or
reactants.
•pure
same
steps
used
calculate
equilibrium
constants are used to calculate equilibrium
• • depend
We
findon
this
various
initial
concentrations
of
each
reactant.
solute.
Where
nat=almost
(moles
ofThe
gaseous
– to
(moles
gaseous
reactants).
N2of
O4(g)
2NO
• When a solution
freezes,
crystals
of
solvent
are
formed
first.
2(g)
• An example is CH4.
• The conjugate base of a substance with negligible acidity is a strong base. Pr
Chapter 16
• In every acid-base reaction, the position of the equilibrium favors the transfer of a proto
stronger acid to the stronger base.
• The use of strong acids and bases as titrants
will be discussed in Chapter 17 (section 17.3).
41,42,43
is the strongest
acid that
can exist
in equilibrium
in aqueous solution.
•Mole
H+ Fraction,
• Basic oxides (also peroxides and
superoxides)
will beMolarity,
discussed
in Chapter
22 (section
22. 5).
and
Molality
–
• OH is the strongest base that can exist in equilibrium in aqueous solution.
37,38,39,40,41,42,43 ••
Common expressions of concentration are based on the number and
of moles
of one
base, respec
6 Weak Acids
Hydronium ions and hydroxide ions are the strongest possible acid
Properties
of
Solutions
18
• can
Recall
that
mass cansolution.
be converted to moles using the molar mass.
exist
in aqueous
Weak acids are only partially ionized in aqueous
solution.
• •Recall:
Stronger
acids react with water to produce hydronium ions and stronger bases r
There is a mixture of ions and un-ionized
acid
in solution.
Properties of Solutions 187
52,53,54,55,56,57,58
Therefore, weak acids are in equilibrium:
moles of component
water +to form–hydroxide ions.
Osmosis
Mole
fraction
of
component
,X
H
O
(aq)
+
A
(aq)
HA(aq) + H2O(l)
3
• This effect
is known
as the
leveling
effect
of water.
moles of all componen
• Semipermeable
membranes
permit
passage
of some
components
of total
a solution.
or
+
–
FORWARD
REFERENCES
•
Often
they
permit
passage
of
water
but
not
larger
molecules
or
ions.
41,42,43
H (aq) + A (aq)
e Fraction, Molarity, and HA(aq)
Molality
• expression
of
semipermeable
membranes
cellbe
membranes
andincellophane.
•• Examples
Acid-base
neutralization
reaction
will
discussed
detail in Chapter 17 (sect
Noteforthat
mole fraction
has noare
units.
We can write an equilibrium constant
this
dissociation:
Chapter
16
234
Common expressions of concentration
are
based
on
the
number
of
moles
of
one
or
more
components.
• Osmosis
is
the
net
movement
of
a
solvent
from
an
area
of
low
solute
concentration
to an area of high
• 17.3).
Note that mole fractions range from 0 to 1.
solute
concentration.
Recall that mass can be converted
to
moles
using
the
molar
mass.
H 3O • AAcid rain will
H beAdiscussed in Chapter 18 (section 18.2).
Recall:
REFERENCES
K a • • Consider
KFORWARD
aor
U-shaped
tube with
a two liquids separated by a semipermeable membrane.
a
Recall:
+
• Inverse relationship
conjugate acids
and bases
beormentioned
inbe
Chm
• moles
H2Obetween
participating
as a Hwill
donor
acceptor will
•HAOne arm of the tubeHA
contains
pure
solvent.in acid-base
molesreaction
of
solute
of
component
Ka is called the acid-dissociation
(section
20.4).
Molarity,
M 18.3).
Mole fraction constant.
of •component
18 (section
The
other, X
arm
containsChapter
a solution.
–
ofa semipermeable
solution
that
Note that the subscript “a” indicates
this
is
the
equilibrium
constant
for
the
dissociation
total
moles
of
all
components
•
Acid-base
properties
in
proton-transfer
reactions
involving OH
, H2O, NH3, etc
• There is movement of solvent in both
directionsliters
across
membrane.
18,19,20,21,22,23,24,25,26,27
(ionization) of an acid.
• • further
Note
that
molarity
will
change
with
a
change
in
temperature
the solution
16.4
Theacross
pH
Scale
As solvent
moves
the membrane,
the fluid
levels in the arms become(as
uneven.
discussed
in Chapter
22 (section
22.1).
Note
omitted from
2O] is fraction
a expression. (H2O is a pure liquid.)
Notethat
that[Hmole
has the
no K
units.
+
Acid-Base
Equilibria
239
• The• vapor
pressure
of solvent
is quite
highersmall.
in the arm with pure solvent.
decreases).
In most
solutions,
[H ] is
the
acid.
The Note
larger that
the Kmole
a, the stronger
15,16
+
range
from
0 can
to 1.
• We
Eventually
pressure
difference
due
to theofdifference
in height ofunit:
liquid in the arms stops
d bases as titrants willfractions
be discussed
in
17
(section
17.3).
in terms
pH.
•the We
express
molality
(m[H
), ]yet
another
concentration
• Chapter
define
16.3
The
of
Water
Ka is larger since there are more
ions
presentAutoionization
at equilibrium
relative
tothe
un-ionized
molecules.
+
Recall:
osmosis.
des and
superoxides)
will
be
discussed
in
Chapter
22
(section
22.
5).
The
pH = log[H ] = log[H3O+].
netwater
reaction
isfollowing
theisautoionization
If Ka >> 1, then the acid is completely
ionized
and the
acid
a strongequilibrium
acid. of water.
• •• In
pure
the
is
established:
+
– osmosis.
Osmotic
pressure
,
,
is
the
pressure
required
to
prevent
moles
moles of solute
• Note that
scale.
H2this
O(l)is a logarithmic
H (aq) + OH
+(aq) of solute
–
43
culating
Ka from pH Molarity, M• Osmotic pressure
Molality,
m
+
2H
O(l)
H
O
(aq)
+causes
OH
obeys
a
law
similar
in
form
to
the
ideal-gas
law.(aq).
2 [H ] by a factor
3
of
10
the pH to change by 1 unit.
•
Thus,
a
change
in
•
Recall
that:
liters
of
solution
Chapter
kilograms
solvent
+of
– ideal gasof
• For
moles,
V=the
volume,
M=
molarity,
R=
the
constant,
and an absolute
n order234
to find
the 16
value of Ka, we
need
to know
all ofnisthe
equilibrium
concentrations.
•
This
process
called
autoionization
water.
•
Most
pH
values
fall
between
0
and
14.
K
w = [H ][OH ]
zed Note
in aqueous
solution.
will change with a change
+
that
molarity
in
temperature
(as
the
solution
volume
increases
or
temperature,
osmotic
pressure
The pH gives the equilibrium concentration
H .this information
• canof
Molality
does
not
with
temperature.
We
use
write
an expression
relates
17tovary
• T,Inthe
neutral
solutions
at is:
25 °C,that
pH =
7.00. the values of Ka, Kb, and Kw for a
un-ionized
acid in solution. The• Ion
+
of
Water
decreases).
+use
–7
we use the pH to findconjugate
theProduct
equilibrium
concentration
of
H
and
then
Thus,
to find Ka REFERENCES
FORWARD
acid-base
pair.
•converting
In+ acidic solutions,
[Hmolarity
]n> the
1.0
10
,)so
pH molality
< 7.00. (m) requires densit
quilibrium:
M
and
•
Note
that
between
(
RT
MRT
coefficients
of
the balanced
equation
to
help
us
determine
thedecreases,
equilibrium
(m),
another
concentration
unit:
We stoichiometric
can define• molality
– •yet
A
ε
bc H
participating
in
acid-base
reaction
as =
a H
donor
or pH
acceptor
willVbe
mentioned
inthe
We
can
write
an
equilibrium
constant
expression
for
the
autoionization
of water.
2+O
•
As
the
the
acidity
of
solution
increases.
Hof
O
(aq)
+
A
(aq)
q) +concentration
H2O(l)
3
+ of dilute solutions
• The molarity and[NH
molality
are
often
very similar.
the other
+
[NH
][H
]exclude
][OH
] –7the
Chapter
18species.
(section
18.3).
+ > 7.00.
3
4
•
In
basic
solutions,
[H
]
<
1.0
10
,
so
pH
•
Because
H
O(l)
is
a
pure
liquid,
we
it
from
expression:
2
Kare
][OH pressure.
] Kw
= –[Hosmotic
• Two
solutions
to be isotonic
if they have the same
moles
of
solute
We then substitute
these
equilibrium
into
the
constant
a Ksaid
bequilibrium
FORWARD
REFERENCES
+
– Molality,
+
m concentrations
oC, K = 1.0x10
-­‐14[NH
]
[NH
•
As
the
pH
increases,
the
basicity
of
the
solution
increases
]
H
(aq)
+
A
(aq)
HA(aq)
18,19,20,21,22,23,24,25,26,27
at 2
5
=
[H
O
][OH
]
=
K
K
3
w
4
•
Hypotonic
solutions
have
a
lower
,
relative
to
a
more
concentrated
solution.(acidity decreas
c
3
w.
expression
and pH
solveScale
for Ka.
16.4
The
kilograms
of
solvent
•
Molar
concentrations
will
be
used
in
rate
law
expressions
in Chapter 14
onstant expression for this dissociation:
• Hypertonic
solutions
have“p”
a higher
, relative to a more dilute solution.
+
pOH
and
Other
Scales
• In most
solutions,
[H
]
is
quite
small.
•
The
product
of
the
acid-dissociation
constant
for
an
acid
(K
)
and
the
base-dissociation
centMolality
Ionization
•
K
is
called
the
ion-product
constant.
a
wWe can•illustrate
Molar
will bered
used
incells.
equilibrium
constant and reaction
does not vary+ with•temperature.
thisconcentrations
with a biological system:
blood
the
strength
terms
of
pH.
• measure
We
express
[HH] in is
• conjugate
We canbase
use
a(K
similar
system
to describe constant
the [OH–for
]. water (Kw):
the
ion-product
constant
for
its
b) equals
Another
of
acid
percent
ionization.
H
O
A
A
M
)
and
molality
(
m
)
requires
density.
Note
that
converting
between
molarity
(
blood
cells
are surrounded
by
semipermeable
in
Chapters
15, ].16,water
17,
19,
and= K20.membranes.
3
+
• • AtRed
25°C,
the
ion-product
is: K
–
= log[H
] = log[H3O+of
Ka –14
].
pOH =+ log[OH
orand
K amolality of dilute•pH
b
w
For
the
reaction,
–intracellular
If
red
blood
cells
are
placed
in
a
hypertonic
solution
(relative
to
there
TheHA
molarity
solutions
are
often
very
similar.
–14
=
K
=
[H
O
][OH
].
1.0
10
•
Concentrations
(ppm)
of
trace
constituents
in
mixtures
willsolution),
be re-introd
+
– we
w
3
• Note that this is aHA
logarithmic
scale.
•
Alternatively,
can
express
this
as:
•
Recall
that
the
value
of
K
at
25
°C
is
1.0
10
.
w
HA(aq)
H is
(aq)
+ A (aq)
a
lower
solute
concentration
in
the
cell
than
the
surrounding
tissue.
+
WARD
REFERENCES
by a factor
of 10
causes
the
pHpK
to
• Thus, a change in•[H ]This
ion constant.
applies
to
pure• water
as
well
to1throughout
aqueous
solutions.
(section
18.1)
and
used
Chapter
+can
pK
=bypK
=a14.00
(at
25
°C)
Thus,
we
describe
relationship
between18.
pH
pOH:
achange
bas
wunit.
•indissociation
Osmosis
occurs
and
water
passes
through
the membrane
outand
of the
cell.
–in Chapter
+
+14.
–
• •that
Molar
will
be
used
rate
law
expressions
Most
pH
fall between
0
and
14.
icates
this isconcentrations
thevalues
equilibrium
constant
for
the
H
• Thus,
larger
K
),
the
smaller
K
(and
the
larger
pK
).
(and
the
smaller
pK
• Athesolution
is
neutral
if
[OH
]
=
[H
O
].
]
log[OH
])
=
pH
+
pOH
= logKw = 14.00.
log[H
a
a
b
b
3
equilibrium
•
The
cell
shrivels
up.
+ acid,
– weaker its
• Inconcentrations
neutral solutions
at•25be
°C,
pH
=in7.00.
% ionization
100%
• Molar
will
equilibrium
and
reaction
quotient
The
stronger
theconstant
conjugate
base
and viceexpressions
versa.
Othe
] process
> [OH
the28,29,30,31,32
solution
•13.5
Ifused
the
+
–7 3This
Colligative
Properties
•[H
is],called
crenation.is acidic.
HA
Measuring
pH
•Chapters
In acidic(H
solutions,
[H
]
>
1.0
10
,
so
pH
<
7.00.
initial
m the Kain
expression.
O
is
a
pure
liquid.)
+
–
15,2 16, 17, 19,
and
20.
• theIfacidity
] solution
<The
[OH
], the
solution
is to
basic.
50solution, there is a higher solute concentration in
•theIf[H
red
blood
cells
are
placed
inSolutions
a hypotonic
• As the pH decreases,
of3O
the
increases.
• properties
most
accurate
method
measure
pH
is toparticles.
use18
a pH meter.
acid.
16.9
Acid-Base
Properties
of
Salt
Colligative
depend
on
number
ofinsolute
• Concentrations
(ppm)
of+ •trace
constituents
in outside
mixtures
will
be
re-introduced
Chapter
+ the
+
–7 cell than
the
cell.
concentration,
[H
]
,
to
the
initial
HA
Percent
ionization
relates
the
equilibrium
H
•
In
basic
solutions,
[H
]
<
1.0
10
,
so
pH
>
7.00.
equilibrium
re ions present
at equilibrium
relative
un-ionized
molecules.
• colligative
A pH meterproperties
consists of a to
pairconsider:
of electrodes connected to a meter that measure
• throughout
Nearly
all salts
are
strong
electrolytes.
• tothe
There
are
four
(section
18.1)
and
used
18.
• Chapter
Osmosis
occurs
and water
moves
into the
cell.
concentration,
. increases,
• [HA]
As the
pH
basicity
of
the solution
increases
(acidity
decreases).
initial
mpletely ionized and the acid is a strong
acid.
• A voltage
that varies
with pH is generated when the electrodes are placed in a
Therefore,
in
exist entirely
of ions.
15 •
•and Base
vapor
pressure
(Raoult's
law).
• salts
The
cellsolution
burstslowering
(hemolysis).
“Acid
Dissociation
Constants
of
Water
Its Associated
Ions”
from
•
This
voltage
is
read
by
theofmeter,
which
isofcalibrated
to
pH.Further R
pOH and Other
“p” Scales• •Acid-base
properties
of salts
are a consequence
theand
reactions
their be
ions
indisplay
solution.
To prevent
crenation
or
hemolysis,
IV
(intravenous)
solutions
must
isotonic
relative to the
5ictorial
Colligative
Properties
16
•
boiling
point
elevation.
–
+
–
•
Dyes
that
change
color
as
pH
changes
are
also
useful.
Analogies
XI:
Concentrations
and
Acidity
of
Solutions”
from
Further
Readings
Ion”
3-D
from
Instructor’s
CD/DVD
• “Hydroxide
Many
salt
ions
can[OH
react
with
water
to form
OH or H Resource
.
•to know
We can
a similar
system
to describe
the
].Model
intracellular
fluids
of cells.
eble
need
all use
of the
equilibrium
concentrations.
– are called acid-base indicators.
Colligative
depend
number
of
solute
particles.
16.2
fromproperties
Transparency
Pack17on
•
freezing
point
depression.
•
They
•
This
process
is
called
hydrolysis.
+
“K
”
Activity
from
Instructor’s
Resource
CD/DVD
].
pOH
=
log[OH
w Everyday examples of osmosis include:
• Football
concentration
H . and Bases: The
–14• Further
Weak
vs.
Analogy”
from
Readings
Indicators
are less precise than pH meters.
There
are
fourofAcids
colligative
properties
to•°C
+consider:
pressure.
• Strong
that theconcentration
value
of
KwAnion’s
atof
1.0
•25H
Ifand
aisosmotic
cucumber
is. placed
in NaCl
solution, it will lose water to shrivel up and become a pickle.
An
Ability
to CD/DVD
React
with
Water
Hquilibrium
to find
theRecall
equilibrium
then 10
use
the
Constant”
Activity
from
Instructor’s
Resource
•
Many
indicators
do not
have aPearson
sharp color change as
a function of pH.
vapor
pressure
lowering
(Raoult's
law).
•
Thus,
we
can
describe
a
relationship
between
pH
and
pOH:
–
Copyright
Inc.
•
A
limp
carrot
placed
in
water
becomes
firm
because waterEducation,
enters via osmosis.
44,45
the balanced
equation
to Strength
help us•determine
theanequilibrium
+
– from
Consider
anion,
XpH
,•Live
as+Lowering
the
conjugate
base
of©
an2012
acid.
Differences
between
Acid
and
Concentration”
Demonstrations
Vapor-Pressure
Most
acid-base
indicators
can
exist
as
either
an
acid
or
a base.
]
log[OH
])
=
pOH
=
logK
=
14.00.
log[H
boiling point elevation.
w
Eating
large
quantities
ofbasic.
salty food
causes retention of water and swelling of tissues (edema).
cies.
• •Anions
from
weak
acids
are
ormic Acid” 3-D Model28,29,30,31,32
from Instructor’s
Resource
CD/DVD
•
These
two
forms
have
different
colors.
freezing
depression.
•• Consider
Water
moves
intoanplants,
to aingreat
osmosis.
ibrium
concentrations
into Instructor’s
the equilibrium
constant
• Resource
acause
volatile
liquid
in
a extent,
closedthrough
container.
Measuring
Methanol”
3-D point
ModelpH
from
TheyCD/DVD
will
increase
pH.
osmotic
Anions
from
aretime,
neutral.
• Thepressure.
most accurate method• to measure
pH isstrong
to
use acids
a pHof
meter.
• After
a18 period
anofequilibrium
will Readings
be established between the liquid
“One-Hundred
Years
pH” from Further
52 © 2012 Pearson Education,
Copyright
Inc.
44,45
“A
Simple
Demonstration
Model
from
Live
Demonstrations
• • of
They
do partial
not
a change
inOsmosis”
pH.that measures
• A pH meter consists of a pair
electrodes
connected
to a of
meter
small
voltages.
19 cause
The
pressure
exerted
by
the
vapor
is
the vapor pressure.
or-Pressure
Lowering
“Do pH in Your Head” from
Further Readings
–
Pressure
of a Sugar
Solution”
from
Demonstrations
• A voltage that varies 53
with
pH is generated
the
electrodes
placed
a solution.
areinamphiprotic.
• “Osmotic
Anions
with ionizable
protons
(e.g., are
HSO
20 when
3 )Live
“pH
Estimation”
Activity
from Instructor’s
Resource
is percenta• ionization.
Nonvolatile
solutes
(with
no
measurable
vapor
pressure)CD/DVD
reduce
ability
of th
54•
Consider
volatile
liquidisinread
a closed
container.
This voltage
by
the
is
calibrated
to display
• meter,
Howwhich
they 21
behave
in water
isofdetermined
by the
relative
magnitudes
of
Ka and the
Kb for
the ion:
“Osmosis
Through
the
Membrane
anpH.
Egg” from
Live
Demonstrations
“Teaching
the
Truth
about
pH”
from
Further
Readings
molecules
to
escape
liquid.
• aDyes
change
color
as55pH
changes
areKalso
useful.
>22K
anionthe
tends
to decrease
theInstructor’s
pH.
• will
If
“Osmosis
and
Animation
Resource CD/DVD
After
period
time,
an equilibrium
be
established
between
thefrom
liquid
and its vapor.
aOsmotic
b, thePressure”
+ that of
–
HA(aq) • HThey
(aq) are
+ Acalled
(aq) acid-base
“The
pH
Concept”
from
Further
56
indicators.
• Therefore,
If Kisbthe
>
, the
anion
tends
to
increase
theReadings
pH.
“Osmosis
and
Egg
Membrane”
from
Live
Demonstrations
• vapor
vapor
pressure
is
lowered.
avapor
pressure
.
The partial pressure exerted57by
the
the
23K
“Defining and Teaching pH” from Further Readings
• solutes
are no
lessmeasurable
precise
than pH
meters.
“Seawater
Gets
Fresh”
from
Further
Readings
51,52,53 of the surface solvent
24 React
Nonvolatile
(with
vapor
pressure)
reduce
the
ability
HIndicators
A
Cation’s
Ability
to
with
Water
“The Symbol
for
pH”
from
58
equilibrium
• Many indicators do not Figure
have a 13.25
sharp color
change
as
a
function
of
pH. Further Readings
from
Transparency
Pack
25
onization to escape the liquid.
100%
molecules
Figure
16.5
from
Transparency
Pack are conjugate acids of weak bases.
•
Polyatomic
cations
that
have
one
or
more
ionizable
protons
• Most
acid-base indicators
an acid or a base.
41 can exist as either
HA initial
26
“An
Alternative
Introduction
to
the
Mole
Fraction”
from
Further
Readings
Therefore,• vapor
pressure
is
lowered.
“Acids
and
Bases”
Activity
from
Instructor’s
Resource
CD/DVD
•
They
tend
to
decrease
pH.
These two forms have
different colors.
Copyright © 2012 Pearson
Education,
Inc.
42
27
“Food
is
Usually
Acidic,
Cleaners
Are
Usually
Basic”
from
Live
Demonstrations
•
Many
metal
ions
can
cause
a
decrease
in
pH.
“Mole
Fraction
Analogies”
from
Further
Readings
+
+