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Chem 2 Test 1


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What is diffusion?
Process where particles of gases, liquids, or solids intermingle as a result of their kinetic properties
what are intramolecular forces?
Forces that cause atoms in a molecule to stay together
What are intermolecular forces of attraction?
forces that attract molecules together
Are intermolecular forces or intramolecular forces greater?
What is the definition of the boiling point of a substance
The temperature at which sufficient energy is supplied to overcome the intermolecular forces
How does intermolecular forces effect the boiling point of a substance?
It increases the boiling point
What are the 3 types of Intermolecular forces?
London Dispersion

Dipole-induced dipole

Are Ion Dipole forces intermolecular forces?
What is another name for london dispersion forces of attraction?
induced dipole-induced dipole
What has london dispersion forces?
What does polarizability mean?
The ease with which the electron distribution in the species can be distorted. Generaly increases with # of electrons
What intermolecular forces are present in non-polar molecules?
only dispersion forces
What happens to the melting point of a substance as the number of electrons in that substance increases
melting point increases
How do you convert celcius to kelvin?
temp C + 273.15
What is dipole dipole forces?
attractive force between polar molecules?
What type of intermolecular force is hydrogen bonding?
What elements can bond with hydrogen in a hydrogen bond?
What are charecteristics of N,O,F that make them want to bond with hydrogen in a hydrogen bond?
2nd row elements
very small atoms
very electronegative
lone pairs of electrons in the hydride form
What are all the intermolecular forces called together?
Van der waals forces
What kinds of intermolecular force happens between a polar molecule and a non-polar molecule?
dipole induced dipole
and dispersion
What kinds of intermolecular forces happens between two polar molecules
dipole dipole and dispersion
What kinds of intermolecular forces happen between two non-polar molecules?
dispersion only
Whats the definition of surface tension?
amount of energy required to stretch or increase the surface of a liquid by a unit area
Does surface tension increase or decease with higher intermolecular forces?
Whats the diffrence between a waxed surface and an unwaxed surface and what do each of them due to a droplet of water on them?
Waxed surface means no H bond and the droplet wants to minimize the surface area and therefor beads. With the unwaxed there are H-bonds and the droplet doesn't minimize its surface area.
What is capillary action?
the ability of a narrow tube to draw a liquid upwards against the force of gravity
what forces cause capillary action?
cohesion and adhesion
what is cohesion and adhesion?
cohesion is attraction between similary molecules
adhesion is attraction between a liquid and a solid
this is what causes water to rise in a tube.
When refering to a straw in water. If adhesion is greater than cohesion will the water rise up in the straw or not?
what is viscosity?
measure of a fluids resistance to flow
T/F the greater the viscosity the less freely a liquid flows.
False the greater the viscosity the more slow the liquid flows
What affects viscosity?
Particle size
intermolecular forces
and temperature
T/F the bigger the molecules the greater the viscosity?
T/F the greater the intermolecular forces the less the viscosity?
T/F the greater the temp, the lower the viscosity?
What is so unique about water in terms of surface tension, specific heat (amount of energy required to raise the temperatrue by 1C) and solid state relative to liquid state?
Very high surface tension
High specific heat
solid is less dense than liquid
What defines a crystalline solid?
Rigid and long range order
sharp/well defined melting point
What defines a amorphous solid?
Lacks well defined arrangement and long range order

No sharp melting point
What is a unit cell?
basic repeating structural unit of a crystalline solid
How many diffrent types of crystalline unit cells are there?
What are the 3 types of cubic cells, how many particles do each have, and where are the particles located for each?
simple cubic- 8 particles located at each corner of the cube

body-centered cubic- 9 particles 8 on corners and 1 in the middle

face-centered cubic- 12 particles, 8 in the corners and 1 more on each face (6 total)
How many atoms per unit cell are there for the 3 main cubic cells (simple, body centered, face centered)?
simple-((1/8)*8)=1 atom

body centered-((1/8)*8+1(center))=2 atoms

face centered-((1/8)*8+(1/2)*6)=4 atoms
What is a coordination number? and what is the coordination number of the 3 main cubic cells?
the number of atoms or ions surrounding an atom or ion in a crystal lattice

simple- 6

body centered- 8

face centered- 12
How many atoms in a simple cubeic cubic cell?
How many atoms in a face centered cubic?
How many atoms in a body centered cubic?
When silver crystallizes, it forms face centered cubic cells. The unit cell edge length is 409pm. Calculate the density of silver.
Bragg equation: n (lamda) = 2dsin (theta) what does everythign mean
d=distance between adjacent planes in the crystal
theta=angle between x rays and plane of crystal
X rays of wavelength 0.154 nm (0.154 x 10-9 m) are diffracted from a crystal at an angle of 14.170. Assuming that n = 1, what is the distance in nm between layers in the crystal?
0.315 nm
What are the 4 types of crystals?
What are some characteristics of ionic crystals?
Lattice points occupied by charged species (cations and anions) held together by ionic bonds
High melting points, hard, brittle
Poor conductor of heat and electricity (ions are fixed in positions)
Note: Anions are much larger than cations
What are some characteristics of covalent crystals?
Lattice points occupied by atoms held together by covalent bonds
High melting point, hard
Poor conductor of heat and electricity
Examples: diamond (C), graphite (C), quartz (SiO2), silicon carbide (SiC)
What are some characteristics of molecular crystals?
Lattice points occupied by molecules held together by intermolecular forces (weaker than ionic or covalent bonds)
Low melting point, soft
Poor conductor of heat and electricity
What are some characteristics of metallic crystals?
Lattice points occupied by metal atoms held together by metallic bonds
Low to high melting point, Soft to hard
Good conductors of heat and electricity
Examples: Mg, Ni, Sn, Cs
What phase has the greatest molecular order?
solid phase
What is dynamic equilibrium?
when the rates of condensation and evaporation are equal
What is equilibrium vapor pressure?
vapor pressure when a dynamic equilibrium exists
What is molar heat of evaporation and what is the symbol?
energy required to vaporize 1 mole of liquid
change Hvap
What is the exact definition of boiling point?
when the temp at which the vapor pressure of a liquid is equal to the external pressure
How does change in heat vaporization coerlate with boiling point?
higher the Hvap the higher the boiling point
Name all the variables in the following equation and what the equation could be used to find:
lnP=-(chng Hvap/RT)+C
P=Equilibrium vapor pressure
R=gas constant (8.314)
What is critical temperature?
temp above which the gas cannot be made to liquify
what is critical pressure (Pc)
min pressure that must be applied to liquify a gas at Tc
What is molar heat of fusion?
energy required to melt 1 mole of a solid, chng Hfus
its the temp at which solid and liquid coexist icewater
Is chngHvap>chngHfus?
What is sublimation?
when solid goes directly to gas
what is molar heat of sublimation?
energy required to sublime 1 mole of a solid
What three things are factors that influence the ease at which a solute will dissolve?
solvent-solvent interaction
solute solute interaction
solvent solute interaction
What is entropy?
inherent tendency toward disorder and intermingling
what is soluability and what are the units?
measure of how much solute will dissolve in a solvent at a specific temp
mol solute/liter solution or
grams solute/100grams solvent
what is miscibility?
ability for two liquids to be compleatly soluble in each other
What kinds of substances are likely to be soluble in one another?
like substances - ones with similar intermolecular forces
What are the 4 types of concentration units?
percent by mass
mole fraction
Give the equation and units for the concentration unit of:
Percent by Mass
% by mass =mass solute/(mass solute+ mass solvent)
Give the equation and units for the concentration unit of:
Mole Fraction (X)
X=moles of A/(sum of moles of all compounds)
Give the equation and units for the concentration unit of:
Molarity (M)
M = moles solute/liters solution
Give the equation and units for the concentration unit of:
m=moles solute/mass of solvent(kg)
What is the molality of a 5.86 M ethanol (C2H5OH) solution whose density is 0.927 g/mL?
8.92 m
T/F does the soluability of a solid increase with temp?
T/F does the soluability of a gas increase with temp?
True for solid

False for gas
Solution of 16.0 g MgSO4 and 100 mL of H2O at 25 °C. What is the mole fraction of each component?
dH2O at 25 °C = 0.997 g/mL
MWMgSO4 = 120.4 g/mol
MWH2O = 18.0 g/mol
What is Henry's Law and what do the variables mean?
c=concentration M of the dissolved cas
P=pressure of gas over solution
k=constant that depends on temp
The concentration of dissolved oxygen in an aqueous solution is 0.44g / 0.1 L solution.
The partial pressure of oxygen above the solution is 150 mm Hg.
What is the predicted oxygen concentration (in g/100 mL) if the partial pressure for oxyge
c2=0.164 g/ml
What are teh 4 colligative properties?
vapor pressure lowering
boiling point elevation
freezing point depression
osmotic pressure
What is Raoult's Law what does it refer to and what are the units and variables?
Psoln=vapor pressure of solution
Xsolvent=mole fraction for solvent
P'solvent=vapor pressure of the pure solvent
What is the vapor pressure at 25 ºC of an aqueous sucrose (C12H22O11) nonvolatile solution that contains 300 g sucrose dissolved in 1000 g water ?
Pºwater = 23.76 torr
23.39 torr
What is the vapor pressure of a solution at 20 ºC that contains water (H2O) and ethanol (C2H5OH) (0.60 mole fraction H2O and 0.40 mole fraction C2H5OH) ?

V.P. of H2O = 17.5 torr at 20 ºC
V.P. of C2H5OH = 44.0 torr at 20 ºC
Ptotal=28.1 torr
What is the equation for boiling point elevation?
ΔTb = (Tb – T°b ) = Kbm
ΔTb = b.p. increase
Kb = b.p. elevation constant
m=molality of solute particles
What is the equation for freezing point depression?
ΔTf = (T°f – Tf ) = Kfm
ΔTf = f.p. decrease
Kf = f.p. decrease
m = molality of the solute particles
What is the freezing point of a solution containing 478 g of ethylene glycol (antifreeze) in 3202 g of water? The molar mass of ethylene glycol is 62.01 g.
chngTf = Kf m
Kf water = 1.86 0C/m
-4.48 degrees C
what is osmosis?
The selective passage of solvent molecules through a porous membrane from a dilute solution to a more concentrated one
What is the equation for osmotic pressure (Ϭ)?
M =Molarity of solution
R = ideal gas constant (0.0821 L.atm/mol.K)
T = Kelvin temperature (absolute T)
What is the diffrence between electrolyte and nonelectrolyte?
non-electrolytic has one mole to one mole of solid = one mole particles in solution
electrolytic is one mole solid = more than one mole particles in solution
What is van't hoff factor(i) in terms of electrolytic solutions?
van’t Hoff factor (i) =
actual number of particles in sol’n after dissociation/
number of formula units initially dissolved in sol’n
when doing boiling point elevation for electrolytic solutions what do we multiply kfm and kbm by?
i which = # particles in solution after/# particles before

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