Unit 8: Gases Flashcards
describe the volume and shape of gases
indefinite volume and shape
do gases tend to have low or high densities
low densities
are gases easily able to mix with other gases
yes, mix with one another readily
what condition causes a dramatic change in the volume of a gas
changing temperature
what are common units of pressure
- mmHg
- torr
- atm
- Pa
- kPa
- psi
what are the conversions for units of pressure
- 1 mmHg = 1 torr
- 1 atm = 760 mmHg / torr
- 1 atm = 101.3 kPa
- 1 atm = 14.7 psi
how is the pressure exerted by a gas measured
- the frequency of collisions between gas molecules and the container walls
- more collisions = higher pressure
what happens to pressure when volume decreases
pressure increases
describe boyle’s law
pressure and volume are inversely proportional
what is the equation for the relation between pressure and volume
P1V1 = P2V2
what happens to volume when temperature decreases
volume decreases
describe charles’s law
volume and temperature are directly proportional
what is the equation for the relation between volume and temperature
V1/T1 = V2/T2
what unit of temperature must be used in all gas law calculations
kelvin
how do you convert celsius to kelvin
273.15 + C
what happens to volume when moles increase
volume increases
describe avogadro’s law
moles and volume are directly proportional
what is the equation for the relation between moles and volume
V1/n1 = V2/n2
what formula can be used to combine all the individual gas laws
P1V1/n1T1 = P2V2/n2T2
what happens to pressure when moles decrease
pressure decreases
are moles and pressure directly or inversely proportional
directly proportional
define the ideal gas law
implies that all gases behave the same way under the same conditions
what is the equation for the ideal gas law
PV=nRT
what does R equal
- PV/nT
- 0.0821 Latm/molK
what is the equation for density of gases
d=P(MW)/RT
are density and temperature inversely or directly proportional
inversely proportional
which gases are more dense: higher or lower molecular weights
higher molecular weights = more dense gas
describe dalton’s law of partial pressures
- Ptotal = P1 + P2 + P3 …
- the pressures of the different types of gases in a sample will add to be the total pressure of the entire sample
- each gases pressure can be determined by multiplying the total pressure by the mole fraction of a gas (mols of one type of gas / total mols)
what are the steps to determining the mass of a gas through stoichiometry
- use ideal gas law (PV=nRT) to determine moles of gas
- perform stoichiometric conversion to get to grams
what are the steps to determining the volume, pressure, or temperature of a gas through stoichiometry
- perform stoichiometry conversions to determine the moles of a gas
- use ideal gas law (PV=nRT) to determine the volume, pressure, or temperature
what are the 5 pillars of kinetic molecular theory
- gases consist of large number of molecules that move continuously and randomly
- the combined volume of the gas molecules is negligible compared to the total volume in which the gas is contained
- attractive and repulsive forces between gas molecules are negligible because they are moving so fast past each other
- the average kinetic energy of the molecules is proportional to the absolute temperature (K)
- all collisions are elastic; no energy lost
is the kinetic energy of gas molecules directly or inversely proportional to temperature (in K)
- directly proportional
- as temperature increases, the kinetic energy increases
are molecular weight and average molecular speed directly or inversely proportional
- inversely proportional
- as molecular weight decreases, speed increases (smaller molecules are faster)
are gases more ideal at low or high pressures and why
- low pressures (0-20 atm)
- low pressure = higher volume = size of molecules is more negligible
are gases more ideal at low or high temperatures and why
- high temperatures
- high temp = high speed = less time molecules spend near each other = less attractive/repulsive forces
