Chapter 6 Gas Flashcards
Properties of Gas
A. Gases have an indefinite shape. B. Gases have a low density C. Gases are very compressible D. Gases exert pressure equally in all directions on the walls of a container. E. Gases mix spontaneously and completely with one or more other gases.
a gas consists of?
small particles that move rapidly in straight lines
- indefinite shape; mix spontaneously
compared to the volume of the container they occupy gas particles have?
very small volumes
- low density; compressibility
gas particles having essentially no attraction or repulsion towards one another means..
they colide frequently with each other and with the walls of the container, the ollisioins are perfectly “elastic”
- no loss of energy
- exert pressure in all direction
- kinetic energy of gas particles affects the pressure/volume
the average kinetic energy (energy of motion) of the gas particles are?
directly proportional ot its absolute temperature
kelvin temperature
what are the 4 variables of the physical behaviors of gases
pressure P
volume V
temperature T
amount n
pressure
the force exerted by gas against the walls of the container
- atm; mm Hg: torr; pascal
volume V
the space occupied by the gas
- L; mL
temperature T
determines the kinetic enegy and rate of motion of the gas particles
- C; K
amount n
the quantity of gas present in a container
- g; moles
Pressure of A Gas
gas pressure is the force acting on a unit area
Pressure P = (Force/area)
- pressure is indicated by Δh (mm) of Hg column
atmospheric pressure
- pressure exerted by a column of air from the top of the atmosphere to the surface of the earth
- about 1 atm at sea level
- lower at high altitudes where the density of air is less
- is affected by weather, being lower on a rainy day than on a sunny day
atmospheric pressure at sea level is about 1 atm = (mmHg, torr, psi, kPa)
1 atm = 760 mmHg (exact) 1 atm = 760 torr 1 atm = 14.7 psi (lb/in.2 ) 1 atm = 101.325 kPa (kiloPascals).
temperature
- the property of a gas is related to the kinetic energy (speed) of the gas particle, thus the absolute temperature kelvin
K = oC + 273.0
the volume of a gas is the
volume of the container it occupies
- L or mL
the property of a gas is related to?
the number of as particles in the same, NOT the nature of gas particles
- moles (av.#)
the 4 variable of a gas PVTn are interdependent
Any one variable can be determined by
measuring the other three.
In the laboratory, scientists often hold 2
variables constant and then observe how the
other 2 variables change with respect to each
other
Boyle’s law (for pressure and volume)
• At constant temperature, the pressure of a fixed amount of gas increases, when the volume decreases. • At constant T and n, V of a gas is inversely related to its P.
Boyle’s law formula
P1V1 = P2V2
Kinetic Molecular Theory: when the volume decreases, the
gas particles moves in smaller space, thus colliding more
often with the wall and exerting higher pressure.
Charle’s Law for temperature and volume
At constant pressure , The volume of a fixed amount of gas is directly related to its Kelvin temperature.
Charles law formule
V1 = V2
__ ___
T1 T2
Kinetic molecular theory of charles law
: As Tk increases, gas particles move
faster and collide more with the wall, thereby expanding the
volume of container until the inside pressure equals the
outside pressure.
Avogradro’s law
for volume and moles of the gas
At constant P and T, the volume (v) of a gas is directly related to the number of moles ( n) of gas
avogrado’s law formula
V1 V2
__ = ___
n1 n2
kinetic molecular theory of avogradro’s law
When the number of gas particles
increases, so does the number of collision on the wall,
thereby expanding the volume until the inside pressure
equals the outside pressure
The ideal gas law formula
PV = nRT
universal gas constant
R = 0.0821 (atm-L/mol-K)
Combined gas law
P1V1 P2V2
____ = _____
T1 T2
(nature of the gas does not matter)
partial pressure
- the pressure of a gas in a mixture
at a given T, in a given container, the pressure of a
gas is the same with or without the presence of other
kinds of gas particle.
The partial pressure of a gas (in a mixture)
is the same as the pressure of the gas
if it were alone in the container
Dalton’s Law of Partial Pressures
The total pressure exerted by gases in a mixture is the
sum of the partial pressures of those gases.
physical states of matters
Gas
indefinite shape
indefinite volume
compressibility
low density g/L
physical states of matter
liquid
indefinite shape
definite shape
not compressible
g/ml density
physical states of matter solid
definite shape
definite volume
not compressible
density g/cm3
Solid kinetic-molecular view
fixed, very close arrangement of particles
very strong interaction between particles
very slow movement of particles
liquid kinetic-molecular view
- random, close arrangement of particles
- strong interaction between particles
- moderate movement of particles
gas kinetic-molecular view
- random, far apart arrangement of particles
- essentially none interaction between particles
- very fast movement of particles
inter-particle attraction in Liquid and Solid
- ionic compound
solid at Tr
- smallest particles = ions
- electrostatic attraction among cations and anions = ionic bonds (chemical bonds)
Inter particle attraction in Liquid and solid
- covalent (molecular compounds)
smallest particle = molecules attraction within molecule= covalent bond (chemical bond) attraction between molecules = intermolecular force (IMF)
3 types of intermolecular force (IMF)
polar covalent compounds - dipole-dipole attraction - hydrogen bonds Nonpolar covalent compounds - dispersion force
dipole - dipole attraction
attractive forces between the
positive and negative “poles”
of different polar molecules.
hydrogen bonds
A very strong Dipole-Dipole Force
found between or in molecules that
contain H-F, H-O, H-N bonds
dispersion forces
weak attraction caused by temporary
dipoles that develop when electrons
are not distributed equally
criteria’s for hydrogen bonds
Hydrogen atoms that are covalently bonded to F, O, and N atoms only may participate in hydrogen bonding. • Similarly, the lone pairs on a F, O, or N atom of another molecule may participate in hydrogen bonding. • There are no exceptions to this
London dispersion force
- transient, weak attraction among non-polar molecules
-LDF is transient
and weak.
Only at very 4.2 K
(-268.8◦C), when He
atoms move very
slowly, attraction by
LDF is strong
enough to hold He
atoms in the liquid
state.
The boiling point
(condensation
point) of He gas is
4.2 K!
Gas - imf
- No IMF
Gas to solid = deposition
gas to liquid = condensation
solid - imf
-High IMF
Solid to liquid = melting
solid to gas = sublimation
liquid - imf
- lower imf
liquid to gas = vaporization
liquid to solid = freezing`
IMF heat absorbed
Sublimiation
melting
vaporization
IMF heat released
deposition
freezing
condensation
