Unit 2 (ch 12,18,14) Flashcards
mixture of solid metals
alloys
Use alloys to…
alter and improve properties of individual metals
Metallic bonds consist of (blank)
shared electron pools
Describe metallic bond
Are electrons easy or hard to pull away?
valence orbitals overlap with neighbors to give delocalized electron pool
-easy
What happens when more metal ions bind together?
End up with a band of valence and/or conduction energy levels (valence and conduction bands)
Semiconductors principle/explanation
valence and conduction bands are separated by a band gap, which varies in energy depending on compounds
larger band gaps =
higher energy between the two bands, harder for electrons to move between them
structures of metals
different, highly ordered ways that atoms can arrange to give a layer organization of metals
What are unit cells?
smallest repeating units, stack together to form crystalline structure
Dimensions of the unit cells are determined by
packing of atoms
length of cubic
2r
BCC radius
0.4330 times length
FCC radius
0.3536 times length
Alloys
different atoms either substitute or fit between the originals
interstitial alloys
new atoms fit between the regular ones
What type of hole has the most space?
cubic
What is the ratio equation for the holes?
r guest/ r host
What is the cubic holes ratio?
0.73-1.00
NaCl is a compound where (blank) holes are filled by
octahedral, Na+ ions
1st law of thermodynamics
energy not created nor destroyed, just transferred
to determine the spontaneity of a process, we look at
entropy of system, surroundings, and universe
2nd law of thermodynamics
energy wants to spread out
Spontaneous means
no input is needed for the process to occur- doesn’t always happen fast
microstates represent
unique arrangements of different options/states
by moving to areas of greater heat/energy or larger volumes, what happens?
more microstates are accessible and entropy increases
molecules have three types of motion/freedom- they are?
vibrational, translational, rotational
at lower temperatures, how does this affect microstates?
fewer accessible microstates, less energy to access more of them
colder things will spontaneously do what?
absorb energy from warmer ones- ice will melt, because liquid water has greater entropy
what processes are isothermal?
melting/freezing and boiling/condensation
define isothermal
energy goes to breaking molecules apart or bringing them together
What does it mean to be a state function? Example?
route from initial to final doesn’t matter, only change and entropy
delta S system =
delta S final- delta S initial
delta S system =
qrev/T (K)
q=
heat that can leave or enter a system from the surroundings
what are forward and reverse processes?
melting and freezing are equal and opposite
for a process to be spontaneous, delta S univ must be
positive
delta S universe =
delta S system + delta S surroundings
Why does ice melt or water freeze spontaneously?
changes in temp give differences in the entropy for otherwise equal and opposite systems
dissolving a solid or diluting a solution is (blank)
- spontaneous
- solute molecules gain more freedom/disorder by entering system, even if some of the solvent molecules become slightly more ordered
interstitial
nonhost fills holes in host
substitutional
host replaced with non-host
types of substititutional
heterogeneous- clumps
homogeneous- random, even distribution
solids are usually composed of
mix of elements
alloy
mixture of metals with the goal of improving the properties of metals (stronger, corrosion resistant, conductive)
what are a few examples of common alloys?
Brass (cu and zn) Stainless steel (Fe and Cr)
metallic bond
shared pool of electrons where atoms are densely packed and valence orbitals overlap
band theory explains what?
sea of electrons
molecular orbits form
valence band
Are metals good conductors?
yes
semiconductors
- electronics
- valence and conduction bands separated by gap
- less energy by shifting atoms
doping semiconductors changes (blank)
band gap
if an element gives extra electrons it (blank)
raises valence bond
if an element gives holes- missing electrons it (blank)
lowers conduction band
if the element gives extra electrons it is known as the
n type (extra negative)
if the element gives holes, it is known as the
p type (extra positive)
no current means there is
no electron flow and electrons stuck in valence bond
current means there is
electron flow and electrons move from valence to conduction band
structures of metals
metal atoms can solidify in highly ordered “crystalline lattice”
hexagonal close packed (HCP) has what type of layering?
ababab
cubic close packed (CCP) has what type of layering?
abcabcabc and each atom touches 12 atoms
what type of cells have the densest packing?
HCP and CCP 74%
packing efficiency
volume of atoms/volume of cell x 100
Cubic
layers just stack on top of each other (52%)
What type of layer does cubic have?
aaaaaa
What type of layering does body centered cubic have?
ababab- 68%
unit cell dimensions are determined by what?
packing of atoms
simple cubic unit cell
length- 2r
one atom per unit cell
1 corner atom per unit cell
body centered cubic unit cell
length- r= 0.4330l
two atoms per unit cell
1 full in middle, 1 corner
face centered cubic
length- r= 0.2526l
4 atoms per unit cell
3 face, 1 corner
alloys
mixture of different metals
subsitutional alloy
-new metal atoms take place of original
3 types of subsitutional alloys
homogeneous
heterogeneous
intermetallic
homogeneous
randomly but evenly distributed
heterogeneous
clumps or groups of replaced atoms
intermetallic
uniform composition and stoichiometry
alloys can make metals
harder (harder for atoms to slide past each other)
interstitial alloy
host stays in pattern and holes are filled with other atoms
types of holes
tetrahedral
octahedral
cubic
tetrahedral
smaller, 4 host atoms, FCC and HCC
octahedral
larger FCC and HCC
cubic
middle of simple cube and when filled looks like BCC
radius of host: other RATIO
r other/ r host
what is the ratio for tetrahedral?
0.2:0.4
what is the ratio for octahedral?
0.4:0.7
what is the ratio for cubic?
0.7:1.0
if there is little carbon, the substance is often
malleable
metals are described as
cations in sea of electrons
what are the types of nonmental cystals?
covalent network
molecular solids
ionic solids
covalent network
solids held together by covalent bonds (e- sharing)
what forms network covalent solids?
C bonds
C-C bonds form
allotropes
diamond formation
4 covalent bonds, carbon (STRONG)
graphite formation
3 covalent bonds-carbon held together with dispersion
fullerenes
soccer ball shaped carbon bonds
molecular solids
molecular held together with imf
range from H bonds and DD (H2O/ice) to ID weak forces holding solid together (CO2, O2S8)
ionic solids
cation and anion, ion-ion force
- bigger ion is in crystal lattice and one in hole
- maintain strict stoichiometric ratio
- ordered structure
Why don’t ionic solids have alloys?
strict pattern and structure
solid, inorganic compound which has been heated
ceramic
what are common ceramics?
Si and SiO2 (silica)
amorphous solid
obsidion, no crystal lattice or order
Superconductors
atoms vibrating resist flowage (super cold = vibrating stops)
characteristics of metallic solids
malleable and breakable
characteristics of ionic solids
hard and brittle
what two types of structures have close packing?
HCC and FCC
what two types of structures have square packing?
BCC and SC
HCC stacking pattern
abababab
FCC/cubic closest packed stacking pattern
abcabc
BCC stacking pattern
ababab
SC stacking pattern
aaa
malleable means
easily bent and damaged
metallic elements have (blank) electronegatives than nonmetals
lower- bonding e not tight
(blank) has more valence than host semimetal
dopant
p type semiconductor
dopant has fewer valance electrons than host
meissner effect
magnet floating above superconducting material
1st law of thermodynamics
energy not created or destroyed, just transferred
energy allows work
spontaneous vs nonspontaneous
do or don’t require intervention of some sort
2nd law of thermodynamics
entropy helps determine spontaneity
energy wants to spread out
universe tends to disorder
for a spontaneous process, the entropy of the universe (blank)
increases
Microstates
unique arrangement of things
-arrangement is energy level
deflating tire
three types of motion for gas molecules
translational, rotational, virbrational
Boltzmann distribution
- indiv. molecules might change energy but system stays same
- shows all possible states a molecule can occupy
higher temp or greater volume gives (blank)
more potential microstates
more microstates means
increased entropy
colder things spontaneously (blank)
absorb energy from warmer things
melting and boiling processes are (blank)
isothermal
entropy is a (blank)
“state function”
what does it mean if something is a “state function”
only initial and final states matter
delta S system
S final - S initial
delta S system or entropy for isothermal process
q reversible/ T (k)
forward and reverse processes are
equal
S univ =
S sys + S surroundings
heat transfer to cooler system is
spontaneous
greater temperature difference =
greater entropy change for univ
entropy related to dissolving solutes in solvents
gain freedom of motion once dissolved
dilution process is
spontaneous- more disorder
3rd law of thermodynamics
at 0 K, entropy=0
Gibbs free energy
delta Hrxn - T(delta S)
If G < 0, S univ
> 0 spontaneous
If G>0, S univ
<0 nonspontanous
If G = 0
no change in system
delta H (-) and delta S (+) delta G = spontaneous or nonspontaneous?
delta G <0
spontaneous
delta H (-) and delta S (-) delta G = spontaneous or nonspontaneous?
delta G <0 at lower temp
spontaneous at lower temp
delta H (+) and delta S (+) delta G = spontaneous or nonspontaneous?
delta G <0 at high temp
spontaneous at high temp
delta H (+) and delta S (-) delta G = spontaneous or nonspontaneous?
delta G>0
not spontaneous
What is the 3rd law of thermodynamics?
“perfect” crystalline material at 0 K, entropy = 0
What does Gibbs free energy relate?
delta S and H sys and the energy available to do work
If delta G = <0, delta S univ > 0, spontaneous or nonspontaneous?
spontaneous
If delta G > 0, delta S univ < 0, spontaneous or nonspontaneous?
nonspontanous
if delta H is - and delta S is + , delta G is? Spontaneous?
always < 0, always spontaneous
if delta H is - and delta S is - , delta G is? Spontaneous?
< 0 at lower temp, spontaneous at lower temp
if delta H is + and delta S is + , delta G is? Spontaneous?
< 0 at higher temp, spontaneous at higher temp
if delta H is + and delta S is - , delta G is? Spontaneous?
always > 0, never spontaneous
system becomes colder, q rev is (blank)
+ (gaining energy)
system becomes hotter, q rev is (blank)
- (losing energy)
What is an example of a coupled reaction?
delta G can power other reactions that are nonspontaneous- combustion of glucose drives ADP phosphorylation to form ATP
kinetics is the study of
rates of reactions
Describe catalytic converters in cars
remove NO
production rate is
+
consumption rate is
-
slope =
- rate
the overall reaction order is the
sum of the exponents
increased molecules and concentration (blank) rate
increases
if a line is linear, it is
first order
pseudo first order
one of reactants is way larger than the other so it becomes the only one that matters
step 1 is the (blank)
slowest
rate determining step
slowest step
if collisions are increased, (blank) increases
concentration
subscripts tell us what?
reaction order
overall rate depends on the (blank) in the rate determining step?
concentrations
1st order reaction in relation to graph
if ln(x) vs t is straight line
activation energy equation
ln (k2)- ln (k1) = Ea/R (1/T2-1/T2)
higher Ea =
slower reaction
if Ea is smaller, reaction is
faster
if Ea is larger, reaction is
slower
if the graph starts at higher energy then goes to lower, the reaction is going to be (blank) and delta H is going to be (blank)
exothermic, negative
if the graph starts at lower energy and goes to higher energy, the reaction is going to be (blank) and delta H is going to be (blank)
endothermic, positive
how to find slope
ln(k1)-ln(k2)/ (1/T1-1/T2)
Reaction mechanisms describe what
molecularity
unimolecular
one molecule in rate
bimolecular
two molecules
three molecules
ter
step 1 is the
rate determining step, slow
rate laws are determined by
the slowest step
