Chapter 8: The Gas Phase
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What is the mathematical realtionship between all the units of pressure?
1 atm = 760 mmHg = 760 torr = 101.325 kPa
What is standard temperature and pressure?
1 atm and 273 K; occupies 22.4 L
What is an ideal gas?
• no intermolecular forces • occupy no volume
What is the ideal gas law?
PV = nRT
What are the units for the R gas constant?
L-atm/mol-K make sure to convert all values to this before substituting
Density is defined as What?
ratio of the mass per unit volume of substance
Avogadro’s principle states what?
All gases at a constant temp and pressure occupy volumes that are directly proportional to the number of moles of gas present
1 mol of any gas, irrespective of its chemical identity, will occupy how many liters at STP?
22.4
Boyle’s law states?
Gas held at constant temperature will have volume inversely proportional to pressure
Charles’s Law states?
At constant pressure, the volume of a gas is proportional to its absolute temperature
Gay-Lussac’s law states?
At constant volume, pressure and temp are directly proportional
Dalton’s law of partial pressures states?
the total pressure of a gaseous mixture is equal to the sum of the partial pressures of the individual components
____________ ____________ is the pressure exerted by evaporated particles above the surface of a liquid
Vapor pressure
Henry’s law: Henry noticed that, at various applied pressures, the ____________ of a gas in a liquid increased or decreased.
concentration
Vapor pressure from evaporated molecules forces some of the gas back into liquid phase and equilibrium is reached between what two processes?
Evaporation and condensation
Kinetic molecular theory makes 5 assumptions about ideal gas behavior. What are they?
• Particle volume is negligible to container volume • No intermolecular attractions • Continuous random motion • All collisions are elastic - conservation of momentum and kinetic energy • Average kinetic energy is proportional to absolute temp of gas
The speed of an individual gas molecule is impossible to define, so how do we define gas speed?
Average molecular speed
What can we use to define average gas speed?
Root mean square speed
What happens to molecules at higher temperatures?
A greater proportion move at higher speeds
Kinetic molecular theory predicts that heavier gases diffuse (slower/faster)? than lighter ones because of their differing average speeds.
slower
Because all gas particles have the same average kinetic energy at the same temperature, what must be true about particles with greater mass?
They travel at a slower average speed
Under isothermal and isobaric conditions, the rates at which 2 gases diffuse are inversely proportion to what?
The square roots of their molar masses
____________ is the flow of gas particles under pressure from one compartment to another through a small opening.
Effusion
Rates of effusion are proportional to what?
Average speeds