Chem #8 Flashcards
gases and liquids are ____
fluids
sphygmomanometer
medical devices that measure blood pressure (mmHg)
Normal BP: 120 systolic and 90 diastolic
understand how a barometer works
Many medical devices use the same conceptual design of a barometer.
• Atmospheric pressure creates a downward force on the pool of mercury at the base of the barometer while the mercury in the column exerts an opposite force (its weight) based on its density.
• When the external air exerts a higher force than the weight of the mercury in the column, the column rises, and vice versa.
ideal gas
hypothetical gas with molecules that have no intermolecular forces and occupy no volume
ideal gas law
shows relationship between Pressure, Volume, moles, and temperature for an ideal gas.
o Used to analyze the relationships between variables when certain ones are held constant.
combined gas law
: changes in temperature, volume, and pressure of a gas
what are the requirements of an ideal gas?
no intermolecular forces and occupy no volume
real gas
: deviate from ideal behavior at high pressures (low volumes) and low temperatures because of intermolecular forces or volume effects.
when do real gases deviate from ideal behavior?
high pressure (low volume) and low temperature
the gas laws show that ____
that all gases show similar physical characteristics and behavior irrespective of their particular chemical identity.
the ideal gas constant for the ideal gas law can be rounded to ____
0.8
the ideal gas constant for the ideal gas law can be rounded to ____
0.08
how to solve for molar mass at STP given density
o Molar mass equals the density at STP x 22.4 L/mol
Holding mass constant for calculations using combined gas law.
avogadro’s principle
all gases at a constant temperature and pressure occupy volumes that are directly proportional to the number of moles of a gas present.
As the number of moles of gas increases, the volume increases in direct proportion.
boyle’s law
for a given gaseous sample held at constant temperature (isothermal conditions) and constant moles, the volume of the gas is inversely proportional to pressure.
As pressure increases, volume decreases.
charle’s law
at constant pressure, the volume of a gas is proportional to its absolute temperature, expressed in K. n and P are constant
As temperature increases, volume increases.
gay lussac’s law
at constant volume, the pressure of a gas is proportional to its absolute temperature in kelvins. n and V are constant
As temperature increases, pressure increases.
dalton’s law of partial pressures
o When two or more gases that do not chemically interact are found in one vessel, each gas will behave independently of the others.
Each gas will exert pressure independently of the other gases, as if it were the only gas present: partial pressure of the gas.
the total pressure of a gaseous mixture is equal to the sum of the partial pressures of the individual components.
Partial pressure of a gas is related to its mole fraction
partial pressure of a gas is related to its ____
mole fraction
henry’s law
The solubility of a gas will increase with increasing partial pressure of a gas.
vapor pressure
: the pressure exerted by evaporated particles above the surface of a liquid
Vapor pressure from the evaporated molecules forces some of the gas back into the liquid phase, and equilibrium is reached between evaporation and condensation.
what are the assumptions of the kinetic molecular theory
o 1. Gases are made up of particles with volumes that are negligible compared to the container volume.
o 2. Gas atoms or molecules exhibit no intermolecular attractions or repulsions.
o 3. Gas particles are in continuous, random motion, undergoing collisions with other particles and the container walls.
o 4. Collisions between any two gas particles (or between particles and the container walls) are elastic, meaning that there is conservation of both momentum and kinetic energy.
o 5. The average kinetic energy of gas particles is proportional to the absolute temperature of the gas (in kelvins), and it is the same for all gases at a given temperature, irrespective of chemical identity or atomic mass.
kinetic molecular theory
explain the behavior of gases.
The higher the temperature, the ____ molecules move. The larger the molecules, the ____ they move.
faster
slower
The average kinetic energy of a gas particle is proportional to the ____ of the gas.
absolute temperature
The average kinetic energy of a gas particle is proportional to the ____ of the gas.
absolute temperature
Maxwell-Boltzmann Distribution Curve
shows the distribution of gas particle speeds at a given temperature.
compare diffusion and effusion
Diffusion: when gases mix with one another
Effusion: when a gas moves through a small hole under pressure.
Both conditions are slower for larger molecules AND USE THE SAME EQUATION
graham’s law
under isothermal and isobaric conditions, the rates at which two gases diffuse are inversely proportional to the square routes of their molar masses
diffusion
the movement of molecules from high concentration to low concentration through a medium (such as air or water)
effusion
: the flow of gas particles under pressure from one compartment to another through a small opening.
• For two gases at the same temperature, the rates of effusion are proportional to the average speeds.
what are the deviations of real gases from the ideal gas law due to high pressure?
o Pressure of gas increases, condensation point is reached, gases condense
o At moderately high pressure, a gas’s volume is less than would be predicted by the ideal gas law due to intermolecular attraction.
o At extremely high pressure, the gases take up a larger volume than would be predicted by the ideal gas law.
o The ideal gas law assumes that a gas can be compressed to take up zero volume which is not physically possible.
what are the deviations of real gases from the ideal gas law due to low temperature?
o Temperature of gas decreases, condensation point is reached, gases condense.
o Same as above:
At moderately low temperature, the gas will have a smaller volume than what would be predicted. DUE TO IMF
At extremely low temperature, gases will occupy more space than predicted by the ideal gas law. DUE TO particles can’t be compressed to 0 volume.
van der waals equation of state: a term
corrects for the attractive forces between molecules (van der waals term for attractive forces)
Small and less polarizable < larger and more polarizable < largest for polar molecules
van der waals equation of state: b term
corrects for the volume of the molecules (van der waals term for big particles)
larger molecules have larger values for b
a term vs b term van der waals equation of state
a term is generally much larger than b
a term: attractive forces
b term: volume
how are the characteristics of gases different than liquids?
gases have the ability to expand to any volume and can be easily compressible.
they are very distanced with weak intermolecular forces.
what 4 variables define the state of a gas?
pressure, volume, moles, temperature
In _____ law, pressure and volume are inversely related
Boyle’s
Equal amounts of all gases at the same temperature and pressure will occupy _____ volume
equal
in ___ law, volume and temperate are directly proportional
Charle’s
adding up all of the partial pressures gives the ____
total pressure for the vessel
the value of Henry’s constant depends on _____
the identity of the gas
all of the ideal gas laws use what units for temperature?
Kelvin
the gas laws demonstrate that all gases _____
show similar physical characteristics and behavior irrespective of their particular chemical identity
the kinetic molecular theory of gases predicts that heavier gasses diffuse ______ than lighter ones because of their different average speeds
more slowly
All gas particles have the same _____ at the same temperautre
average kinetic energy
trends with increased pressure and decreased temperature regarding ideality
initially the gasses have lesser volume then would be predicted and then they would have greater volume than would be predicted.
1000 cm^3 = ?
1 L
