Exam 1 Study Guide Flashcards
Dispersion force
all liquids/solids experience; weakest force
- increases w/ increasing molar mass
London force
dispersion force for nonpolar species
dipole-dipole interaction
- polar molecules
- higher melting and boiling points
hydrogen bonding
F-H, N-H, O-H
- highest melting and boiling points
hydrophilic
water-soluble
- ions, polar molecules, H-bonds
hydrophobic
water-insoluble
- hydrocarbons (alkanes)
boiling point increases w/ increasing ___
- increasing molar mass
- increasing polarity
- increases greatly w/ hydrogen bonding
branching disrupts ___
the amount of surface area molecules that interact
- decreases van der Waals interaction–>
- decreases boiling point
dipole-dipole interactions, dipole-induced-dipole interactions, and dipole-induced-dipole-induced interactions occur b/w what molecules?
- dipole-dipole interactions: polar and polar molecule (no H-bonds)
- dipole-induced-dipole interactions: polar and non polar
- dipole-induced-dipole-induced interactions: nonpolar and nonpolar molecules
triple point
- pressure and temperature at which solid, liquid and gas of a pure substance coexist in equilibrium
- the lowest pressure at which the liquid phase can exist
below the triple point…
solid –> vapor or vapor –> solid
critical temperature
lowest temp liquid and gas coexist
melting point: molecular, ionic, metallic, covalent
- molecular: low (lowest)
- ionic: high
- metallic: hard to predict
- covalent: very high (highest)
conductivity: molecular, ionic, metallic, covalent
- molecular: poor conductor
- ionic: poor conductor
- metallic: excellent conductors
- covalent: poor conductor
strength: molecular, ionic, metallic, covalent
- molecular: soft
- ionic: hard but brittle
- metallic: ductile, malleable
- covalent: very hard and very brittle
sheen: molecular, ionic, metallic, covalent
- molecular: dull
- ionic: dull
- metallic: shiny
- covalent: dull
Is rate dependent upon concentration? Why or why not?
yes, as concentration increases, rate increases
What is the significance of k? Is it dependent upon pressure? Temperature?
- k = rate constant
- depends on temp (not pressure)
The half-life of which order reaction (0,1,2 which?) is independent of concentration?
1st
the unit of a rate constant is always
M^-(order-1)*S^(-1)
For which order reaction would reactant A be totally consumed in twice the half-life of the reaction?
0th order
For which order does the concentration of the reactant decrease by 1⁄4 in twice the half-life of the reaction?
1st
define equilibrium
rate forward = rate backwards
- forming reactants at same rate forming products
Is an elementary step the same as an elementary reaction?
yes
What is the rate-limiting step?
- the slowest step
- determines overall rate of reaction
- Rslow = Roverall
what is an intermediate?
produced and consumed but not in overall reaction
- right –> left side (products –> reactants)
t/f: rate law depends on intermediates
FALSE (independent of intermediates, must substitute in rate expressions)
what is a catalyst?
produced and consumed but not in overall reaction
-left –> right side (reactants –> products)
Is concentration of catalyst allowed in a rate law (rate expression)?
it could be used
activation energy
minimum energy to start a reaction
activation energy depends on…
the substance (NOT temp, pressure, or concentration)
how does a catalyst impact activation energy?
decreases
K = ?
= K(forward)/K(backward)
= k1/k-1
= [products]^# / [reactants]^#
formation reaction
forming 1 mole of a compound from the 2 elements in their natural temp and pressure
what does a large K value mean?
mostly product at equilibrium, very little starting material
a small K value means…
mostly starting material, very little product
What quantity represents the extent of reaction?
how much product is made at equilibrium
K = 1 means…
molarities of reactions = molarities of products
K < 1 means…
favors the reactants
K > 1 means…
favors products
atoms with lone pairs are usually more ____, and differences in electronegativity between two atoms results in ____
electronegative
polarity
when are gases permanent gases at room temperature (25 dC?)
Tc < 25 dC
how does polarity effect boiling point? nonpolar?
polarity increases boiling point
- nonpolar has lower boiling point
polarizability depends on ____
molar mass (more polar = larger molar mass)
unit for k is found by ?
M^-(order - 1) S^(-1)
Rate =
change(concentration)/change(time)
The activation energy of a reaction A + B → C depends upon what property?
the nature of reactant species
What are minimal requirements for two molecules to react to form product?
- molecules must approach with the right orientation
- molecules must collide with minimal energy required to break bonds ( ≥ EA)
define reaction mechanism
Sequence of elementary steps (in complex reaction) describe in detail how the reaction proceeds
R overall ~ =
R slow
write the rate law for given steps:
Roverall = Rslow
- R = k (reactants slow)^(stoichiometry)
- substitute for intermediates
equation to solve for order “m” or “n”
Ln (R1/R2) = m * Ln(A1/A2)
where is the triple point on the phase diagram? the critical point?
triple point- where all 3 line segments meet
critical point- end of far line
what phase is below the line on the phase diagram? top left? top right?
- bottom: gas
- top left: solid
- top right: liquid
Common network covalent elements and compounds
common: Si, SiC, SiO2 (quartz), C (diamond), C (graphite), BN, Ge, ReB2, AIN
UNITS for temperature in Arrhenius equation
KELVIN (C + 273.15)
what substances are taken into account for the equilibrium constant expression (K)?
gases (g) and aqueous solutions (aq)
- not solid or liquids
- K = (products)/(reactants)
(Ms)^-1 = what order?
2nd
Le Chatelier’s Principle
if a system at equilibrium is disturbed by some change, then the system will shift so as to entirely or partially counteract the effect of the change
examples of changes for le chatelier’s principle
- Adding or removing gaseous reactants or products
- Changing the volume or pressure of system
- Changing the temp
(LC) adding a gaseous species to the products will shift equilibrium to the
left
(LC) removing a gaseous species from the products will shift equilibrium to the
right
(LC) adding a gaseous species to the reactants will shift equilibrium to the
right
(LC) removing a gaseous species from the reactants will shift equilibrium to the
left
Le Chatelier’s principle does not include…
- liquids or solid
- a gas that doesn’t react with another species
(LC) increasing volume will shift equilibrium to…
the side with more gas moles
(LC) decreasing volume will shift equilibrium to…
the side with fewer gas moles
(LC) increasing pressure will shift equilibrium to…
the side with fewer gas moles
(LC) decreasing pressure will shift equilibrium to…
the side with more gas moles
(Van Hoff’t) endothermic (+), raising temp shifts the equilibrium…
to more products
(Van Hoff’t) endothermic (+), lowering temp shifts the equilibrium…
to more reactants
endothermic reactions…
need energy
exothermic reactions…
don’t need energy (have enough)
(Van Hoff’t) exothermic (-), raising temp shifts the equilibrium…
to more reactants
(Van Hoff’t) exothermic (-), lowering temp shifts the equilibrium…
to more products
(Van Hoff’t) exothermic (-), lowering temp shifts the equilibrium…
to more products
Would addition of a catalyst to a reaction increase the equilibrium constant?
NO- The only thing that changes an equilibrium constant is a change of temperature
what effects the equilibrium constant value?
ONLY temperature
Adding mass to one side, shifts equilibrium towards
The opposite side
Relationship between pressure and volume
Inverse (one increases, other decreases)
Delta (H) < 0 =
(-) delta H
Exothermic
Delta(H) > 0 =
(+)
Endothermic
Diatomic elements
Have no fear of ice cold bear
(Hydrogen, nitrogen, oxygen, iodine, chlorine, bromine)
concentration = —/—-
Mol / Volume
Reverse rate constant = (K)^?
K^(-1)
Q =
(products)/(reactants)
Q = K =
at equilibrium
Q ≠ K =
not at equilibrium
Q < K =
reaction moving to the right (products)
Q > K =
reaction moving to the left (reactants)
The addition of a buffer gas or of a pure solid (or pure liquid) causes ____ effect.
no effect
equilibrium table: extent of the reaction = ___ units
x atm
breaking bonds….
requires energy (endothermic)
making bonds…
releases energy (exothermic)
