Download Chp 19- reaction rates and equilibrium

Thank you Athena and Kristen.
Chp 19- reaction rates and equilibrium
 Collision Theory
If collisions are efficient reactants will form products. If collisions have enough
KE reactants will form products.
 Activation Energy and the curve depicting it
Refer to book
 Factors affecting reaction rates
Catalyst, particle size (smaller increases reaction rate), concentration, and
temperature
 Equilibrium and factors affecting it- Le Chantelier’s Principle
2NO(g) + O2 (g)   2NO2(g) + heat
1. increase [O2] : products favored
2. increase temperature: reactants favored (favors side that heat is not on)
3. increase pressure: products favored (count particles, side with less are favored
then pressure increases)
 Find equilibrium constant
aA x bB  cC x dD
Keq = [Products] = [NO2]
[ ] = mol/L
[Reactants]
[NO]2 x [O2]
Keq < 1 = products favored
Keq > 1 =reactants favored
 What makes reactions spontaneous? –understand rate of entropy and heat
(enthalpy)
Increase entropy – lost of disorder
} spontaneous
Decrease energy/ enthalpy (exothermic) } spontaneous
(negative Gibbs free energy) -*delta*G0
Chp 12
 Variables affecting gases
Pressure, temperature, volume and moles (P T V n)
Increase volume = decrease pressure
Increase pressure = increase temperature
Increase moles = increase pressure } directly proportional to temp and indirectly
proportional to volume
 Gas laws
P1 x V1 = P2 x V2
T1
T2
When conditions do not change use PV=nRT, R is the constant about 8.31 but she
will give to us on a test.
 Ideal vs Real
Real gases DO have attractive forces and have volumes that are significant
Ideal gases are perfect because they do not take into consideration attractive
forces and volumes.

Gas mixtures and movements: Avagadros hypothesis, Daltons Law and Grahams
law
Avagadros: gas under same conditions has same volume; empty space in between
differs but over all volume will stay the same because KE is the same.
Daltons: each particle has KE the same collision/pressure, therefore they are
additive: Ptotal= P1 + P2 + P3 … etc
Grahman: gas effusion rate directly proportional to
1
(square root of)Molecular mass
KE = ½ MV2 meaning smaller particles moving faster get out of containers first
because they are less likely to hit something.
Chp 10
 Kinetic theory
See notes : gas particles are small hard spheres
 Gas pressure
* results from collisions* collisions of other particles and container
 Phases --> solid liquid gas
 Sublimation solid to gas with no liquid stage
See phase diagram
Chp 11
 Chemical potential energy
Energy stored in the bonds of a substance C – C – H
 System, surroundings and universe
 Endothermic and exothermic
Endothermic: heat moves into system causing it to feel cold to the surroundings
Exothermic: heat moves into the surroundings, causing the surrounds to heat up.
Reactants chemicals have more “beginning energy” that the products
 Calorie
1000 calories = 1 Calorie
1 calorie can raise 1g of water 1 degree C
 Enthalpy (heat)
Energy change at constant pressure
 Thermochemical equations
A + heat = B is endothermic
A = B + heat is exothermic
 Hess’s law
Additive reactants and products, therefore additive heat change due to law of
conservation of matter and energy
Lack of final reaction you need, you can manipulate the reactions and add up all
chemicals to get the final heat or reaction.
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Final Study Guide
Last semester review:
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Atom—the smallest particle of an element that retains the properties of that element;
Daltons atomic theory—all elements composed of tiny indivisible particles called atoms,
atoms of same element identical and different from other elements, atoms of different
elements can physically mix or chemically bond in simple whole-number ratios to form
compounds, chemical reactions occur when atoms are separated, joined, or rearranged,
they are never changed into atoms of another element due to chemical reaction.
Ions—atoms or groups of atoms with a positive or negative charge; cation = “paws”itive,
anion = negative
Parts of atoms—electrons = negatively charged; protons = positively charged; neutrons =
no charge but mass nearly equal to proton; atomic number = # of protons; mass number =
total # of protons & neutrons; # of protons = # of electrons; isotopes = same # of protons
but different # of neutrons
Energy and electrons—energy level = the region around the nucleus where the electron is
likely to be moving; quantum = amount of energy required to move an electron up to the
next level of energy
Conversions—better remember this, or else I don’t know where I’ve been all year!!!
Names—um…what is this referring to?
Bond characteristics—ionic bond = forces of attraction that bind oppositely charged ions,
when melted or dissolved in water can conduct electricity; metallic bonds = the attraction
of free-floating valence electrons for the positively charged metal ions, conductors,
ductile (can be drawn into wires), malleable (can be hammered or forced into shapes);
single covalent bond = where two atoms share a pair of electrons (double and triple are
with two and three pairs); coordinate covalent bond = when one atom contributes both
bonding electrons; nonpolar covalent bond = when the atoms in the bond pull equally;
polar bond = when the bonding electrons are shared unequally
Polarity— electronegativity difference 0.0-0.4 nonpolar covalent, 0.4-1.0 moderately
polar covalent, 1.0-2.0 very polar covalent, 2.0+ ionic
Etc…
Chapter 7
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Mole—6.022 x 1023 representative particles of a substance
Avagadro’s number—6.022 x 1023
Representative particle—species present in a substance: usually atoms, molecules, or
formula units (ions)
Molar mass—the mass (in grams) of one mole of a substance
Volume of a mole of gas—22.4 L @STP
STP—standard temperature and pressure; standard temperature = 0°C; standard pressure
= 101.3 kPa or 1 atmosphere (atm); use because volume of gas varies with a change in
temperature or a change in pressure
Know your calculations!!!
Chapter 8
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Balance and be able recognize different types of reactions—page 222-223 in the book
Net ionic reactions—the equation that indicates only those particles that actually take part
in the reaction; get rid of spectators!
Spectators—ions that are not directly involved in a reaction
Chapter 9
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Stoichiometry—that’s the thing you use to calculate amounts of stuff in chemical
reactions; SHOULD KNOW THIS BY NOW!!!
Dimensional analysis—again, if I don’t know this, how would I have gotten as far as I am
now!!
Limiting reagents—the thing that determines or limits the amount of product that can be
formed in a reaction; reaction only occurs till it’s used up
Percent yield—the ratio of the actual yield to the theoretical yield; theoretical yield = the
maximum amount of product that could be formed from given amounts of reactants;
actual yield = the amount of product that actually forms when performing experiment;
actual yield x 100%
theoretical yield
Chapter 10
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Understand kinetic theory—tiny particles in all forms of matter are in constant motion;
all gas composed of particles that are small hard spheres w/insignificant volume,
relatively far apart w/empty space between, no attractive/repulsive forces between them,
move rapidly in constant random motion, in straight lines till they collide with other air
particles, “random walk,” all collisions perfectly elastic (total KE remains constant)
Gas pressure—the force exerted by a gas per unit surface area of an object
Molecular arrangement and general structure of different phases—crystal = when the
atoms, ions, or molecules that make up the solid substance are arranged in an orderly,
repeating, three-dimensional pattern called the crystal lattice; unit cell = the smallest
group of particles within a crystal that retains the geometric shape of the crystal;
allotropes = two or more different molecular forms of the same element in the same
physical state; amorphous solids = solids that lack an ordered internal structure; glasses =
amorphous solids that are products of inorganic substances that have cooled to a rigid
state without crystallizing, sometimes called supercooled liquids
Sublimation—the change of a substance from a solid to a vapor without passing through
the liquid state
Chapter 11
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Understand key terms
Chemical potential energy—energy stored within the structural units of chemical
substances
System—the part of the universe on which you focus your attention
Surroundings—everything else in the universe
Universe—the system and the surroundings
Conservation of energy—states that in any chemical or physical process, energy is
neither created nor destroyed; all can be accounted for as work, stored energy, or heat
Endothermic—a process that absorbs heat from the surroundings; feels cold
Exothermic—a process that releases heat to its surroundings; feels warm
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calorie—the quantity of heat needed to raise the temperature of 1 g of pure water 1°C
enthalpy—(H) for systems at constant pressure, the heat content is the same as the
property of enthalpy
heat of reaction—heat change for the equation exactly as it is written; usually reported as
ÄH, the heat change at constant pressure; can be included in equation; remember molar
heat of combustion, fusion (melting), solidification, vaporization, condensation, and
solution (when solute dissolves in solvent) all for one mole of substance
thermochemical equations—equations containing the heat change; can be within equation
or on the side
Hess’s Law—if you add two or more thermochemical equations to give a final equation,
then you can also add the heats of reaction to give the final heat of reaction; additive
reactants & products therefore additive heat change due to laws of conservation of
mass/matter & energy; look at what you need for final reaction; manipulate reactions and
add all things up (chemicals & heat), cancel things out
Chapter 12
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Variables affecting gases and their relationships to one another—pressure (proportional
to temperature), temperature, volume (indirectly proportional to pressure), number of
moles (proportional to pressure proportional to temperature proportional to 1/volume)
Be able to apply the various gas laws—for proportional, divide variables; PV = nRT
use when there is no change in conditions P1 x V1 = P2 x V2
T1
T2
Ideal vs. real gases—real gases have attractive forces, significant volume; ideal gases
cannot be liquefied or solidified; gases can be close to ideal at low pressure, high volume
and high temperature (ex: at the top of a very high & hot mountain)
Properties of gas mixtures and movements. Know the WHY of Avogadro’s hypothesis,
Dalton’s Law, and Graham’s Law—Avogadro’s hypothesis is that equal volumes of
gases at the same temp and pressure contain equal # of particles; empty space in between
differs, KE is the same; Dalton’s law of partial pressures is that at constant volume and
temp, the total pressure exerted by a mixture of gases is equal to the sum of the partial
pressures of the component gases, each particle has KE therefore same collision/pressure
therefore additive, Ptotal = P1 + P2 + P3...; Graham’s law of effusion is that the rate of
effusion of a gas is inversely proportional to the square root of the gas’s molar mass, KE
= 1/2mv2
Chapter 19
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Understand Collision Theory!!!!!—atoms, ions, and molecules can react to form products
when they collide, provided that the particles have enough KE; particles lacking the KE
to react bounce apart when they collide; collisions have to be efficient enough or have
enough KE
Understand activation energy and the curve depicting it—the minimum amount of energy
that particles must have in order to react; see notes or figure 19.5 on page 535
Factors affecting reaction rates—Catalyst, particle size (smaller the size, greater the
reaction rate, more surface area), concentration, temperature
Understand equilibrium and the factors affecting it—Le Chatelier’s principle—his
principle states that if a stress is applied to a system in dynamic equilibrium, the system
changes to relieve the stress; factors affecting it are concentration, temperature, pressure
(go towards less gas particles
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What makes reactions spontaneous (and what is a spontaneous reaction)—understand the
role of entropy and heat play—spontaneous reaction = reaction that occurs naturally and
that favor the formation of products at the specified conditions; increased entropy and
decreased enthalpy (exothermic) makes reactions spontaneous; Gibb’s free energy
change = the maximum amount of energy that can be coupled to another process to do
useful work; negative value for Gibb’s free energy = spontaneous reaction;
ÄG = ÄH – TÄS (temp in Kelvin’s)