Test 3 – Chemistry Test Answers

Flashcard maker : Elizabeth Hill
properties of gas
expand to fill container and its shape, low density, compressible, mixtures are homogeneous, fluid
structure of gas
composed of particles traveling very fast, move in straight lines until encountering either wall or another particle
kinetic molecular theory
gas particles are constantly moving, attraction between particles is negligible, particle bounce off each other and continue moving (elastic collisions), large empty space between particles, average kinetic energy of particle is directly proportional to kelvin (in temp, in speed)
gas particle pushing
gas molecules constantly in motion, when strike a surface they push that surface, force exerted by gas molecules hitting the entire surface at one instant = pressure that gas is exerting
the result of the constant collision between atoms or the molecule in a gas and the surfaces around them. pressure = force/area
effects of gas pressure
gas will flow from high to low pressure, if somethings in its pas it will try to push it along (wind)
pressure of gas depends on..
number of gas particles in a given volume, volume of the container, average speed of the particles (depended on temperature)
air pressure
atmosphere exerts a pressure on everything (average 14.7 psi)
column of mercury supported by air pressure, force of the air on the surface of the mercury balanced by the pull of gravity on the column of mercury, evangelista torricelli
atmospheric pressure vs altitude
high up means lower atm pressure, rapid changes in pressure causes ears to pop cause of imbalance of pressure
boyle’s law
at constant mass and temperature, volume is inversely proportional to pressure, PV=constant
standard conditions
standard pressure = 1.00 atm; standard temperature = 0C=273K; STP= standard temperature and pressure
charles’ law
volume is directly proportional to temperature (kelvins) V1/T1=V2/T2
gay-lussac’s law
pressure is directly proportional to temperature (kelvins) P1/T1=P2/T2
absolute zero
the theoretical temperature at which gas would have zero volume and no pressure 0 Kelvin, never attainable
combined gas law
law that predicts what happens when the volume of a sample of gas when both the pressure and temperature change P1V1/T1=P2V2/T2
avogadro’s law
volume is directly proportional to the number of gas molecules, equal volumes of gases contain equal numbers of molecules, V1/n1=V2/n2
ideal gas law
use when you have a gas whose condition is changing PV=nRT
molar mass of gas
mass in grams/moles
partial pressure
each gas in the mixture exerts a pressure independent of the other gases in the mixture, sum of all the partial pressures of all the gases in a mixture equal the total pressure
finding partial pressure
multiply the total pressure of the mixture by the fractional composition of the gas
oxygen starvation leads to unconsciousness and death
oxygen toxicity
to much oxygen leads to muscle spasms, tunnel vision, and convulsions
nitrogen narcosis (rapture of the deep)
to much nitrogen
mixture of helium and oxygen
vapor pressure
partial pressure of the water vapor
molar volume
there is so much empty space between molecules in the gas state that the volume of the gas is not effected by the size of the molecules (under ideal conditions)
properties of liquids
high densities compared to gases, fluid, takes shape of container, keep volume (doesn’t expand), cannot be compressed
properties of solids
high densities, nonfluid, keep their own shape and volume, cannot be compressed
crystalline solids
particles arranged in an orderly geometric pattern
amorphous solids
particles do not show a regular geometric pattern over a long time
solid -> liquid, adding heat energy increases kinetic energy of molecules and then overcomes attractive forces holding them.
liquid -> gas, adding heat increases kinetic energy, soon overcomes attractive forces
surface tension
liquids tend to minimize their surface area and resists penetration. the stronger attractive force between molecules, the larger surface tension
the resistance of a liquid’s flow because of strong attractive forces
the process of molecules of a liquid breaking free from the surface, physical change from liquid -> gas (vapor)
factors effecting rate of evaporation
volatile liquids that evaportate quickly, nonvolatile liquids do not evaporate quickly, increasing SA increases evaporation, increasing temperature increases rate, weaker attractive forces means faster rate
gas -> liquid, the vapor molecules may eventually bump into and stick to the surface of the contain or get recaptured b the liquid
dynamic equilibrium
opposite processes that occur at the same rate in the same system
vapor pressure
the partial pressure exerted by the vapor, depends on temperature and strength of intermolecular attractions
the temperature is high enough for molecules in the interior of the liquid to escape
boiling point
the temperature at which the vapor pressure of the liquid is the same as the atmospheric pressure (1 atm)
process in which heat flows into a system from the surroundings and causes surroundings to cool (evaporation), solids melting
process in which heat flows out of a system into the surroundings and warms the surroundings (condensation), liquids freezing
heat of vaporization
the amount of heat needed to vaporize one mole of a liquid, endothermic, depends on the initial temperature
melting point
you heat a solid, its temperature increases until it reaches the point, latent heat fusion
heat of fusion
the amount of heat needed to melt one mole of a solid
a physical change in which the solid form changes directly to the gaseous form, skipping liquid form, endothermic
effect if the strength of intermolecular attractions on properties
stronger attractions take more energy to separate, stronger attractions have higher boiling, melting points, and heat vaporization
why are molecules attracted to each other
+ion and -ion, + – end of polar molecules, larger charge = stronger attraction
dispersion forces (london forces,instantaneous dipoles)
caused by distortion in the electron cloud of one molecule inducing distortion in the electron cloud on another and can lead to a temporary dipole and leads to attractions between molecules
strength of dispersion force
how easily electrons can move, or be polarized, the more electrons and the farther they are from the nuclei, the larger the dipole that can be includes. larger molecules = larger forces
permanent dipoles
a separation of charge resulting from the unequal sharing of electrons between atoms
dipole-dipole attraction
polar molecules have a permanent dipole, the + end of one molecule will be attracted to the – end of another
intermolecular attraction and properties
all molecules are attracted by dispersion forces, polar molecules are attracted by dipole-dipole attractions and have a strong attraction then nonpolar molecules
attractive forces and properties (solubility and miscibility)
like dissolves like, polar molecules dissolve in polar solvents, nonpolar molecules dissolve in nonpolar solvents, if has both polar and nonpolar ten hydrophilic-hydrophobic competition
immiscible liquids
when liquid pentane, a nonpolar substance, is mixed with water, a polar substance, the two liquids separate because they are more attracted to their own kind of molecule than to the other
hydrogen bonding
HF,OH,NH have strong intermolecular bonds, high melting, boiling, and solubility. when it loses the electron the nucleus becomes dishielded, and the exposed proton acts as a very strong center of positive charge
H-bonds vs. chemical bonds
hydrogen bonds are not chemical bonds, hydrogen bonds are attractive forces between molecules, chemical bonds are attractive forces that make molecules
crystalline solids
molecular crystalline solids, ionic crystalline solids, and atomic crystalline solids
ionic crystalline solids
solids whose composite units are formula units, the smallest electrically neutral collection of cations and anions that compose the compound, higher melting point
molecular crystalline solids
solids whose composite units are molecules, low melting
atomic crystalline solids
covalent (effectively one giant molecule), metals (islands of cations in a sea of electrons)
water (unique and important)
all three states on earth, most common solvent, supports life, liquid at room temperature, high boiling point, expands when freeze
the dissolved substance (minority)
the substance solute dissolved in (majority)
aqueous solutions
solutions in which the solvent is water
when one substance (solute) dissolves in another (solvent)
when one substance does not dissolve in another
when matericals dissolve, the solvent molecules surround the solvent particles due to the solvent’s attractions for the solute
two liquids that are mutually soluble
the maximum amount of solute that can be dissolved in a given amount of solvent, concentration
the maximum amount of solute that will dissolve in that solvent at that temperature
can dissolve more solute
super saturated
holding more solute than they should be able to at that temperature, unstable, precipitate
substances whose aqueous solutions is a conductor of electrivity
strong electrolytes
all the electrolyte molecules are dissociated into ions
none of the molecules are dissociated into ions
weak electrolytes
a small percentage of the molecules are dissociated into ions
solubility of liquid vs temperature
high temp = high sol, low temp = low sol
purifying solids: recrystallization
when a solid precipitates from a solution, crystals of the pure solid form b arranging the particles in a crystal lattice because it reject impurities. make a saturated solution of it at high temperatues and then it cools and the precipitated solid will have much less impurity than before
solubility of gas vs temperature
many gases dissolve in water, solubility of gas in a liquid decreases as the temperature increases
solubility of gas vs pressure
directly proportional to its partial pressure, solubility of a gas in a liquid increases as the pressure increases, high pressure = high solubility
low amounts of solute per amount of solution
high amounts of solute per amount of solution
mass percent
the sum of the masses of solute and solvent, [mass solute (g)/mass of solution (g)] x 100%
preparing a solution
need to know the amount of solution and the concentration of solution you want to prepare
solution concentration molarity
moles of solute per 1 liter of solution, describes how many molecules of solute in each liter of solution, molarity = mole of solute/liters of solution
dilution formula
Concentration x Volume=Concentration x Volume
colligative property
any solution property whose value depends only on the number of dissolved solute particles (freezing point, boiling point, osmotic pressure of a solution)
moles of solute per 1 kilogram of solvent, moles of solute/kg of solvent
freezing point depression
the freezing point of a solution is always lower than the freezing point of a pure solvent
molal concentration (freezing)
the difference between the freezing points of the solution and pure solvent is directly proportional, ΔTf=m*Kf
boiling point elevation
the boiling point of a solution is always higher than the boiling point of a pure solvent
molal concentration (boiling)
the difference between the boiling point of the solution and pure solvent is directly proportional, ΔTb=m*Kb
the process in which solvent molecules pass through a semipermeable membrane that does not allow solute particles to pass
osmotic pressure
pressure that is needed to prevent osmotic flow of solvent

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