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Chapter 14: Solutions and Their Behavior
polarity-decides whether two things will mix
emulsifier- helps two things mix and stay mixed
solution-homogenous muxture in which no settling occurs
suspension-particles settle out (ex. muddy water)
solvent-substance in which solute is dissolved, usually greater amount
(water)
solute-sibstance dissolved in solvent
solvation-particles of solute oriented in cluster around solvent molecules
(no rxn)
hydration- same but solvent is water
more ions in solution, greater electricity conductor, lowers freezing
pt
Two factors influencing Dissolution:
1. energy change(delta
H)--positive=endothermic, negative=exothermic--favor in more neg (exo-)
2. entropy change(delta
S)--high=increase disorder, low=decrease disorder--favor if high (more)
(one or both
are needed for dissolution to occur)
enthalpy(heat of solution)-amt of heat released or absorbed upon dissolution
-deltaHsoln
= exothermic (less than starting)
+deltaHsoln = endothermic (more than starting)
increase T increase rate of dissolution (higher disorder)
starting energy for dissolution from surroundings
Crystal Lattice Energy-deltaHxtal, CLE--amt of energy released when
one mol of each constituent in
gas phase forms
1 mol solid (gas has higher energy state than liquid)
methle, ethle, prople,butle,pentle,hexle
-ane=alkane straight chain carbon all single bonds CnH2n+2
-ene=alkene double bond
-ine= alkine triple bond
Solids in Liquids:
what allows
solid to dissolve (deltaHsoln)?
1. deltaHxtal
2. deltaHsolvation--amt energy required to form 1 mol of each constituent
in aqeuoue phase
from gas phase.
Liquid-Liquid:
miscibility-ability of one liquid to dissolve in another
same interactions 1.)solute-solute
2.)solvent-solvent
3.)solute-solvent
"like dissolves like"-polar in polar(attraction) and nonpolar in nonpolar(enthropy)
Fractional Distilation-sparate two liquids
Gas-Liquid:
3 requirements for dissolution in H20
1. must be polar,must ionize in water (ex.HCl, HBr, HI)
2. can hydrogen bond with water (ex. HF)
3. can react with water (ex. CO2)
colder water = higher dissovled O2/CO2 levels (more gas put in to put
heat back)
Rate of Dissolution and Saturation:
1. Agitation: (mix,shake...)break solute, more surface area, more particles
in contact with solvent
2. Heating(endo) and cooling(exo): LeChatllier
3. Increase pressure of gas in gas/liquid
4. increase surface area
Effect of Temp on Solubility:
1. LeChatellier's Principle-when stress is applied to a system at equilbirium
the system responds by
moving in the
direction that alleviates the stress (analyze thermodinamics to see which
direction)
2. saturation-concentration of colute is as high as possible in solvent
as given pressure and temp
supersaturated-higher
than normal
Effect of Pressure on Solubility: (applies to gas/liquid)
1. P of gas above liquid directly proportional to amy gass dissolved
in liquid (Pgas=KCgas)-Henry's Law
Molality and Mole Fraction:
1. molality(m)-#moles of solute per kg solvent (ideal soln)
2. Mole Fraction (X)-Xa=#molA/(#mol A +#mol B....), no dimensions
Colligative Properties:
-properties of soln depend on # not kind of people
1. Lowering of Vapor Pressure: exerted by a vapor at dynamic equilibrium
with its liquid of solid
-vapor pressure
fluctuates depending on how easy it is for solvent molecules to "escape"
-increase in
rate of evaporation = increase in vapor pressures
-adding solutes
to liquids lowers v.p.
1. # solvent particles in contact w/air is lower there for vapor pressure
of soln is lowered
2. entropy-net change higher in pure solvents going to vapor than for soln
-Raoult's Law:
vp solvent in solution directly proportional to the mole fraction of solvent
present
Psolvent=Xsolvent x Ppuresolvent ==> Psolvent=Xsolute x Ppuresolvent
2. Boiling Point Elevation
-boiling point
of liquid is point at which vp = 1atm
-at boiling
point of pure solvent, vp of soln isnt 1atm
-solute particles
impede solvent leaving soln
3. Freezing Point Depression:
-soln lowes
vp of pure solv, soln must freeze at lower temp than pure solv
-concentration
of soln left after solv begins to freeze is higher, freezing is point at
which solid
particles and liquid particles at equilibrium
-soln requires
lower freezinf point to establish equilibrium
-# solid particles moving to liquid is higher because solid is pure solvent
(high conce to low)
-to reestablish equil, solid particles move to liquid phase(melt)
-cool system to prevent particle movemeent (freezing continues)
4. Osmotic Pressure:
osmosis-diffusion
of H20 from high concentration to low concentration of H2O across semi-
permiable membrane
osmotic pressure
(pi)-required to stop osmosis
pi=(nRT)/V or pi=(MRT)/V (for extremely dilute soln M=m
so pi=(mRT)/V )
Solutions that are Electrolytic:
-increase concentration=increase
phenomenon of association=decrease molality=increase error
-Van't Hoff
factor=i = change in temp actual/change theor or Kf actual/theor or m actual/theor
Colloids: solution in which solute like particles(dispersed phase) are
suspended in dispersing medium
(solvent)--based
on particle size
-clodyness from
size of particle, large enought to scatter light (Tyndall Effect)
-hydrophillic
(water-loving) or hydrophopic (water fearing)
Emulsification and Adsorbtion:
-adsorbtion-adhere
to surface of something
-emulsification-"coat"
particles and allow them to stay in dispersed phase
-micelle- polar
head and nonpolar tale, form circle around nonpolar with tale inside,
surface acting agent, adsorbtion
Chapter 15: Chemical Thermodynamics
-energy changes in physical and chemical processes
1st Law of Thermodynamics:amt of energy in universe is constant (Law
of Conservation), energy
cannot be created
or destroyed
system-substances involved in the chemical the chemical/physical changes
studied
surroundings-everything in systems environment
universe-system + surroundings
state funtion-functins that are independent of pathway (P,V,T, etc)
enthalpy changes-change in heat content of a system that accompanies
a system at constant P
(qp or deltaH)
calorimetry-based on obervable changes in temp-one can make assumptions
q= mass x specific
heat x temperature change
in water it takes 4.184J of energy to move 1g up 1 degree C
lost =released,
exothermic, negative sign
gained-endothermic, positive sign
delta Hrxn - the amt of heat released or absorbed per mole of reaction
(kJ/mol rxn)
Thermochemical Equations-balanced chemical equations w/delta Hxn
value, coefficients=moles
assign each
spscies a state (gas has higher delta H than liquid H20)
mol rxn-heat evolved from the # moles of each substance shown in balanced
equation
Standard State and Standard Enthalpy Changes
-thermochemical standard state university-species most stable state
at 1 atm pressure and
25 degrees C
(298K)
-standar conditions specified by superscript "0"
-for delta H rxn 0, everything takes place at constant temperature
and pressure
Bond Energy-amt energy necessary to break 1 mol of bonds in gaseous
covalent substance to form
products in
the gaseous state at constant T & P (limited to gas phase rxns), useful
to estimate
deltaHrxn=sumBEreactants
- sumBEproducts
Internal Energy, deltaE-all energy held by system, represents all energy
contained within the
substance, state
function, diff btw Eprod and Ereact = deltaE
deltaE=Efinal-Einitial=Eprod-Ereact=
q+w=heat + work
deltaE=deltaH
when deltaV=0
must have gas
in product and reactants and diff moles in product to reactant
Sign Conventions: +q=absorbed by system -q=released
by system
+w=on sys by surr (compression)
-w=by sys on surr (expansion) (coonstant T/P)
Compression:
w=FD=PdeltaV
Expansion:
w=-PdeltaV
w=-PdeltaV
deltaV negative (V2 less than V1)
deltaV positive (V2 more than V1)
w= (-)(+)(-)
w=(-)(+)(+)
w=+
w=-
Relating H and E:
deltaH=deltaE + PdeltaV ==>deltaH=q+w+PdeltaV ==>deltaH=q + (-PdeltaV)
+ PdeltaV==>deltaH=q
PdeltaV=delta(n)RT, so, deltaE=deltaH-delta(n)RT if delta(n)=0 then
deltaE=deltaH
Spontaneity of Physical/Chemical Changes:
-will chemical rxn/physical changes occcur w/no outside influence?
-spontaneous rxn:products are more stabble (lower energy) than reactants
(higher energy)
-nonspontaneou rxn:opposite
Thermodynamic
Spontaneity has nothing to do with speed
Two parts of
spontaneity:
1. enthalpy-favored to be exothermic but isnt required
2. entropy-favored by increase insystem, but not required (universe must
increase)
2nd Law of Thermodynamics:
Universe tends towards greater state of disorder
Entropy,S-measure
of disorder of system (related to probability)
deltaSuniv=deltaSsys + deltaSsurr
-not practical to measure deltaSuniv, ppractical to measure deltaSsys
3rd Law of Thermodynamics:
entropy of a perfectly pure crystalline solid (perfectly ordered) at
0K is 0 (entrophy always positive)
deltaSrxn=sum (n)deltaSprod -sum (n)deltaSreact
(units J/(mol K))
Predicting Spontaneity, deltaG Gibbs Free Energy:
deltaG = deltaH
- TdeltaS
Gibbs Free Energy-decrease
in free energy (-deltaG) represents maximum energy obtainable
in form of work (spontaneous: -deltaH and +deltaS) ---- deltaG=0 then equilibrium
The Standard Reaction: all of the reactants are completely converted
to products (constant T,P)
deltaGrxn=sum:(n)deltaGfprod
- sum:(n)deltaGfreact (25 ddegrees, 1atm)
Spontaneity's Dependence on Temperature:
delta H
- &nnbsp;
delta S +
delta G - always
spontaneous
delta H
- &nnbsp;
delta S -
delta G ? spontaneous
below temp
delta H
+
delta S +
delta G ? spontaneous
above temp
delta H
+
delta S -
delta G + never
spontaneous
To find equilibrium temp: deltaG=0 so T=deltaH/deltaS
Chapter 16: Chemical Kinetics
-the study of rates of reaction and mechanism by which they occur
-spontaneity no indicator of speed
Determining Rate of Reaction:
-units: concentration
per unit time
[ ] <-concentration
can't have negative
rate-- place neg infront of rate expression
average rate:
reciprical coefficent (delta [ ] / delta time)
instant rate:
derivatives
Factors that affect reaction Rate:
nature of reactants-
aq soln, increase surface area of solids
concentration
of reactants: rate law expression
rate=k [A]^x
[B]^y
k--rate constant, proportionality constant, specific to reaction, changes
in response to
catalyst & temp, doesnt change w/time
x,y--order of reaction w/respect to concentration, not related to coefficients,
determined
experimentally, usually integers (fractions/neg)
x+y = total order of reaction
zero order-rate
has nothing to do w/concentration of reactant
1st order-rate
directly proportional to concentration
2nd order-directly
proportional to square of concentration
Figuring Out Rate Law Expression--Method of Initial Rates
1.) pick 2 experiments
in which other concentration stays same
2.) find ration
bwt concentration and rate
Concentration vs. Time: The integrated rate expression
-allows analysis
of change in concentration over time
-allows determination
of 1/2 life (amt time to convert half product to reactant)
-varies w/reaction
order
Zero Order:
1st Order:
2nd Order:
rate law expr
rate=k
rate=k[A]
rate=k[A]^2
k units
M s^-1
s^-1
M^-1 s^-1
int rate law
[A]=[A]o -akt
ln ([A]o/[A])=akt
1/[A] - 1/[A]o =akt
half life
t1/2= [A]o/2ak
t1/2= .693/ak
t1/2=1/ak[A]o
Collision Theory of Reaction Rates: increase collisions, increase
temp, increase concentration
effective collisions-must
have sufficient energy for collision to break bonds
-molecules must collide in proper orienntation w/respect to e/o
Transition State Theory: A+B2--->AB + B + heat
Eaf-forward
activation energy-amt enegy needed to break appropriate bonds
reaction intermediate-
(A---B---B)-high energy, unstable, formed, consumed
Ear-reverse
activation energy, energy needed for reversal
delta E- neg
(exo) pos (endo)=Eaf-Ear
activation energy-amt
to get to tansition state
Rxn Mechanism-step by step pathway froom reactants to products
rxn order-for
any single elementary step in mechanism are related to coefficients
rxn can never
occur faster than slowest step (determines rate law)
fast equilibirum
step before slow then affects slow & rate expression
rate forward
= rate reverse in equilibirium
Arrhenius Equation: average kinetic energy of a collection of molecules
proportional to temp
A-constant,
proportionality constant relating to frequency if collisions and propability
that collisons
will occur effectively, same units as k
Catalyst-some that you put into the reaction that increases the rate,
but is not sonsumed in reaction
allows rxn to
occur by alternate pathway that lower Ea
Homogenous-catalyst
in same phase as reactants
Heterogeneous-not
in same phase as reactant, metallic, d-block-easy to move valence electrons
Enzyme as Biological Catalysts:
most enzymes
are proteins w/molec weights from 10^4 to 10^6 amu
very specific-some
catalyze only one reaction
lock and key
model--
active site-place on enzyme where reaction occurs
turn over rates for typical enzymes 10^3 to 10^7 rxns per time period
enzyme inhibitors-fit
active site, heavy metals --mercury in nervous system
Chapter 17 Chemical Equilibrium:
Equilibrium Constant (K) derived from rate constants
-dimensionless
-assume ideal gas/soln
-depends on
temp, doesnt depend on initial conc, constant at given temp
-changes w/changes
in balance reaction Kc^n (raise to reaction factor),
reverse is one over Kc
Reaction Quotient (Q) defines same as K --- products over reactants
raised to each coefficient
Q=K --equilibrium
Q<K shift to reactants
Q>K shift to products
Effecting Equilibrium:
1. increase
conc-- shift to use up increase
2. pressure-
gas phase only-- increase partial pressure decrease volume->shift to side
w/less gas
decrease partial pressure increase volume -> shift to side w/more gas
3. temp- decrease
shift to exo, increase shift to endo
4. catalyst-
no effect, changes time to get to equilibrium (ratef=rater)
Partial Pressure and K:
Kc=Kp(RT)^(-delta
n) Kp=Kc(RT)^(delta n) delta n= (prod-react)
Thermodynamics:
delta G=delta
H- TdeltaS deltaG=
-RTlnK
delta G pos,
K>1 spontaneous deltaG
neg, K<1 nonspontaneous
deltaG 0, K=1 equilib
Evaluating K at different Temps:
ln(K2/K1) =
delta H/R x (1/T1 -1/T2)
Chapter 18 Ionic Equilibria I: Acids and Bases:
Autoionization of Water:
pure water inoinzes
to slight extent Kw=[H3O+][OH-]= 1 x 10^14
[H3O]=[OH]= 1 x 10^7
at 25 degrees
in pure water and dilute aq solns
pH and pOH scale
neg log [H3O]
= pH neg log [OH] = pOH
[H3O]=10^ -pH [OH]=10^ -pOH pH+pOH=14
Disassociation Constant for Weak Acids and Bases:
Ka -- acid
Kb-- base same as Kc
Common Ion Effect and Buffer Soln:
same ion present
in soln from two diff compounds
Types of Buffers:
weak acid + salt of weak acid
weak base + salt of weak base
Henderson-Hasselbach Equations for Buffer Systems
conditions:
conc of acid/salt >.05 M, cation must be univalent
pH=pKa + log
[salt]/[acid]
pOH=pKb + log [salt]/[base]
Buffering Action
-buffers must
maintain relatively constant pH, must control excess H+ and excess OH-
-weak acid/salt
of weak acid buffer
-add excess acid, combines w/anion to fform acid(shift to weak acid)
-add excess base, combines w/H+ (shift right), w/autoionization of H2O
(shifts left)
-weak base/salt
of weak base buffer
-add excess base, combines w/anion to fform base (shifts to weak base)
-add excess acid, combines w/ OH-(shiftt right), w/autoionization of H20
(shifts left)
Polyprotic Acids:
-ionization
occurs stepwise, 1 proton at a time
-strong polyprotic--1st
no Ka, 2nd equilib
Chapter 19: Hydrolysis and Titrations:
Hydrolysis-rxn of substance w/H2O (usually salts)
Salt classifications: product of stong acid/strong base, strong a/weak
b, weak a/strong b, wk a/ wk b
1. Salt of Strong Acid/ Strong Base---Neutral
cation and anion
come from strong base/acid so dont eact w/ H+, OH- so neutral
2. Salt of Strong Acid/ Weak Base-- Acidic
cation of weak
base-->strong acid so salt is acidic
3. Salt of Weak Acid/ Strong Base -- Basic
anion of weak
acid-->stong base so salt is basic
4. Salt of Weak Acid/ Wak Base -- depends on Ka/Kb of acid/base
Kw=Kb x Ka
Salts w/ Highly Charged small cations act as weak acids
Titration Curves:
-equivalence
pt-pt at which chemically equiv amts of acid/base reacted, 1/2 up long
curve
-strong/strong
- indicator phenolthalein (change in baasic), methyl red (change in acid
range)
-strong b/weak
a-indicator phenolthalein
-weak b/strong
a-indicator methyl red
-weak/weak-no
indicator, pH meter, conductivity
Chapter 20: Ionic Equilibria III: The Solubility Product Principle
(Ksp):
-involves equilibrium of slightly soluble compds
-Ksp = product of conc of constituent ions raised to the power that
corresponds to the # of ions
in one formula
unit
-Ksp constant and constant temp for saturated soln of compd
-molar solubility- # of moles of compd that dissolve to give 1L of
saturated soln
-Ksp values can be calculated indirectly
-conflict btw molar slubility and Ksp (to compare compds, compds need
same # ions/ formula unit
-Ksp and Common Ion Effect -- less dissolution
-Rx Quotient (Q) in ppt rxns used to determine max [ions] in soln
Q>K reverse
favored (precip forms)
Q=K equilib Q<K
forward favored (can add more)
Fractional Precipitation:
-method by which
one can remove some ions from soln while leaving others w/similar prop
in soln
Simultaneous Equilibria:
-many wk acids
and bases react w/ metal ions to form insoluble compds
Chapter 21: Electrochemistry:
electrochemistry--chemcial changes produced by electrical currents,
electric produced by chem rxns
all electrochemical rxns involve transfers of electrons (redox)
electrical conduction- voltaic cells
-deal w/spontaneous rxns, no need for outside power source (deltaG
is neg)
-cell is device-- e- transfer takes place through an external pathway,
rather than directly btw reactants
electrodes-metal sheets
-anode- electrode at which oxidation occurs
-cathode-elctrode at which reduction occurs
-neg only when electrons leave from it, other is postive becauase neg
goes to positive
Cell potential (EMF, Eo cell, cell volatage)
-potential of the cell to produce electricity (based on Epotential)
-electrons move from higher Ep to lower Ep - difference in Ep is cell
potential
-measured in volts (V=J/C) 1e- = 1.6 x 10^-19 C (energy per charge
unit)
-Eo cell -- standard conditions: 25o C, 1atm, 1M
Standard Reduction Potential (Eo red)
-cell potential (Eo cell) of any voltaic cell depends on the two half
reactions involved
-each 1/2 cell is assigned 1/2 cell potential
-difference btw half cell potentail is Eo cell
by convention: potential associated w/each electrode is written as
reduction potential
-standard hydrogen electrode (SHE)-reference electrode 0.000V
-more active-lower reduction potential-more likely to be oxidized
Corrosion:
-redox rexns in which metal is attacked by some substance in its environment
(O2, H2O) and
converted into
anothe substance
-oxidation of metals- Al forms outer film not allowing O2 or H2O in
(oxidation stops Al2O3)
-corrosion of iron: increase ph decrease oxidation, increase
salt increase oxidation
-preventing Fe corrosion: paint/oil, coast w/less active metal (problem
in coating compromised),
coat with more
active metal (cathodic protection, sacrificial anode)
Electrolysis
-add energy to a cell to force nonspontaneous reaction to occur
-Down's cell for electrolysis of molten NaCl
-more positive than H20 red potential then can disosolve in H20 (no
need to melt)
-in an aqueous environment
reduction possibilities:
cation or water (which ever is more positive is easier to force)
oxidation possibilities:
anion or water (which ever is easier to force) unless num <.8 difference
Electrical Energy
-# moles of electrons used or produced in redox rxn can be measured
by monitoring current in
external circuit
-current, I, measured in amperes (A), charge/time, Coulombs/sec
-1 faraday= charge per mol of electrons = 96500 C / 1 mol e-
Walther Nerst and the Nerst Equation
E= Eo - (2.303RT/nF) log Q
deltaGo= - nFEocell
Commercial Voltaic Cells:
Battery-one or more (series- several voltaic cells connect + to -,
cells EMFs are additive) voltaic cells
used to generate
electricity (ex. auto battery - to charge apply current in opposite directon)
Chapter 25 Coodination Compounds:
-involve coordinate covalent bonds (unshared e- pair)
-Lewis Acids accept unshared e- pairs (transition metals), Lewis Bases
donate
-Alfred Werner - figured out how covalent comps bond
- counter ion- uncoordinated ion to balance coordinate part
-ligands - Lewis Bases
-simple - 1
e- pair (one atom), unidentate; complex- bidentate (2) ....
-donor atom- atom in ligand that donates e- (more than 1 donor atom-
polydentate)
-chelate-metal atom & polydentate ligand
-coordination number - # donor atoms to which metal is attached (not
necessarily # ligands)
-coordination sphere - metal ion & ligands, but no counter ion,
can have charge
Chapter 27 Organic Chemistry:
-compunds containing C-C and C-H bonds (originally plant/animal origin)--carbon
always 4 bonds
-single bond (4 atoms, sp3) double bond (3 atoms, sp2), triple bond
(2 atoms, sp)
-single bond: head on overlap 1 sigma bond
-double bond: 1 sigma, 1 pi bond (side to side overlap)
-triple bond: 1 sigma, 2 pi bonds
-alkanes- each carbon bonded to 4 atoms, saturated hydrocarbons, only
single sigma bonds