Chapter 10 Concepts Flashcards
Boyle’s Law (description)
As constant mass and temperature, the pressure and volume are inversely proportional (as pressure increases, volume decreases).
Boyle’s Law (equation)
PiVi = PfVf
Charles’ Law (description)
The volume of a fixed mass of gas at constant pressure is directly proportional to its Kelvin temperature (as temperature increases, volume increases).
Charles’ Law (equation)
Vi/Ti = Vf/Tf
Gay-Lussac’s Law (description)
The pressure of a fixed amount of gas, at constant volume, is directly proportional to its Kelvin temperature.
Gay-Lussac’s Law (equation)
Pi/Ti = Pf/Tf
Combined gas law (equation)
PiVi/Ti = PfVf/Tfu
Avogadro’s Law (description)
Equal volumes of all ideal gases at the same temperature and pressure contain the same number of moles/molecules (as number of moles increases, the volume increases).
Avogadro’s Law (equation)
ni/Vi = nf/Vf
Molar volume
Mv = V/n (volume/number of moles: L/mol)
Molar volume of ideal gas as STP
22.4 L/mol
Kinetic-Molecular Theory
1) Gases consist of large numbers of molecule in continuous, random motion.
2) Gas molecules have insignificant volume of their own (compared to the total volume of the container they are in)
3) Molecules have no significant forces between each other or the container they are in
4) Collisions are completely elastic and thus do not use up energy
5) The average kinetic energy of the molecules is proportional to the absolute temperature.
Effect of a volume increase at constant temperature
- Average kinetic energy of molecules remains unchanged
- Average speed/rms speed is unchanged
- Greater distance between molecules/fewer collisions, so pressure decreases
Effect of a temperature increase at constant volume
- Average kinetic energy/rms speed increases
* More collisions with walls of container means increased pressure.
Effect of molar mass on molecular speeds
Molecules with lower molecular masses have higher rms/average speeds.
Effusion
The escape of gas molecules from a container through a hole into an evacuated space (only happens when they happen to hit the hole).
- So rate of effusion is directly proportional to the rms/average speed of the molecules.
- Size of molar mass also affects rate of effusion - lower molecular weight molecules escape faster than higher molecular weight molecules.
Diffusion
The spread of one substance throughout a space or throughout a second substance. (such as the scent of perfume throughout a room)
- Slower than molecular speeds due to collisions.
- Faster for lower mass molecules than for higher mass ones.
van der Waals equation (purpose of it)
As real gases compress with lower temperatures, there will be attractive forces between them, resulting in gases liquefying. Gases at high pressures cannot use ideal gas equation to predict pressure-volume properties either. Equation helps to predict behavior of real gases. Accounts for attractive forces between gas molecules and molecular volumes.
van der Waals equation corrections
- Constant a - measure of how strongly the gas molecules attract each other. (because attractive forces between molecules tend to reduce the pressure)
- Constant b - measure of small but finite volume occupied by the gas molecules themselves. (because molecules don’t have the whole volume to move in, but only the space not already occupied by the other molecules)
Density
D = m/V (mass per volume: g/L)
Molar mass
Mm = m/n (mass per number of moles: g/mol)
STP
273.15 K, 1.00 atm
Dalton’s Law of Partial Pressure
Ptotal = P1 + P2 + P3 + … + Pn
1 atm = ? mm Hg
760
1 atm = ? torr
760
1 atm = ? psi
14.7
1 mm Hg = ? torr
1
Density (d)-Molar mass (M) Equation
PM = dRT d = m/V = PM/RT
Gas constant (R)
0.08206 L-atm/mol-K
Ideal Gas Equation
PV=nRT
Molar mass (M)-Density (d) Equation
M = dRT/P
To find only the pressure of a desired gas collected over water…
…one must subtract the vapor pressure of water from the total pressure
Average kinetic energy relates to rms (root mean square speed) how?
Equal to the square of the rms. As temperature increases, the average kinetic energy increases, and the rms increases by its square.
