gases Flashcards
Kinetic-Molecular Theory (KMT) of Gases Based on what three assumptions?
- The gas consists of molecules of mass in ceaseless random motion, obeying the laws of classical mechanics
β Particles move at constant velocity in straight lines between collisions (with other particles or container) - The size of the molecules is negligible (their diameters are much smaller than the average distance travelled between collisions)
- Molecules interact only through brief elastic collisions
RMS speed of the gas depends on the ______ of the gas, M, and the gasβs temperature (k)
molar mass
_____ is one number that describes the speed of
molecules with given molar mass and temperature
π£πππ
For _____ temperatures and large masses, low speeds
predominate
low
For ____ temperatures and small masses, the
distribution spreads out toward higher speeds
high
If we know the average speeds of particles, we can figure out the average speed with which they
collide, called the _________
mean relative speed
At constant V, Since π£πππ β π£ππππ β π£πππ β π, collision frequency _______ with temperature
increases
At constant T, the collision frequency is __________ to pressure
directly proportional
At constant T, increasing N or decreasing V would ________ pressure, which would increase collision frequency
increase
Collision frequency _______ with increasing T because the particles are moving faster
increases
Collision frequency _________ with P because the particles are closer together and donβt need to move as far in order
to collide, thus causing more frequent collisions
increases
If n is increased, P will ________ without changing T
increase
If T is fixed but P goes up, π will go down. P and π
are _______ proportional
Inversely
π is ___________ of T
independent
We know the ideal gas law is an approximation
that pretends that what?
1) gas particles do not interact except during collisions
2) gas particles
themselves have no volume
Real gases behave most ideally when P is very _____
and/or T is very high
low
When T is ______ (close to condensation) or P is high, gas behavior deviates significantly from ideality
low
When gas particles are very close, they _____ each
other
repel
When gas
particles are
close, but not
very close,
they ________
each other
attract
Ideal gas particles, with no attractive interactions, would never form a ________ or solid
liquid
Real gases
- Particles actually attract one another
β Particles have non-neglible volume
At large V and high T, the isotherms for real gases
are very similar to those of i____________
deal gases
One correction is in terms of the volume (related to virial equation of state)
β Ideal gas law assumes particles occupy no volume
β vdW equation says particles do occupy volume, which
reduces the free volume particles can travel through
β b is the excluded volume per mole, so the free volume
becomes π β ππ
What does PEMDAS mean?
- Parentheses
- Exponentiation
- Multiplication
- Division
- Addition
- Subtraction
The atom is an __________, spherical entity
composed of a positively charged central nucleus
surrounded by one or more negatively charged electrons.
electrically neutral
The atomic nucleus consists of ________ and neutrons.
protons
Charge
β Proton (+) and electron (β) have equal but opposite charges
β Neutron is electrically neutral (no charge)
Mass
β Proton and neutron have very similar masses
β Electron has much smaller mass than proton or neutron
Location
β Proton and neutron are in the nucleus
β Electrons are found outside the nucleus
Atomic number (Z)
Number of protons in an atomβs nucleus
Each element has a ________ atomic number
unique
Atoms are neutral, so number of electrons is what?
equal to atomic number
Mass number (A)
Sum of protons and neutrons in an atomβs nucleus
________ are atoms of a given element with the same number of protons, but a different number of neutrons.
Isotopes
Isotopes have the same atomic number, but a different _________
mass number
Atomic mass is a weighted average of the mass numbers of ____________
all isotopes
If the mean free path is written in as a combination equation with z then how does mean free path vary with pressure?
If n increased, P will increase without changing T
If T is fixed but P goes up, mean free path (π) will go __________
down
To quantify the reduced pressure exerted by real gases we the _______
compression factor ( π = ππ/
πβπ) (Where ππ is the molar volume (V/n) and ππΒ° is the molar volume of an ideal gas at same T and P)
Using the Ideal gas law, what is another way to write the compression factor?
π = πππ/
π
π (or πππ = π
ππ)
What are the two ways of expressing the virial equation of state?
- πππ = π π 1 + π΅β²π + πΆβ²π2 + β―)
- πππ = π π ( 1 + π΅/ππ + πΆ/π^2π+ β―)
The van der waals equation corrects the ideal gas law to replicate gas __________
behavior
What is the first correction the van der waals equation makes?
- is in terms of the volume
β Ideal gas law assumes particles occupy no volume
β vdW equation says particles do occupy volume, which
reduces the free volume particles can travel through
β b is the excluded volume per mole, so the free volume
becomes π β ππ
What is the second correction the van der waals equation makes?
is in terms of the pressure
β Ideal gas law assumes particles donβt interact
β However, they actually attract each other, which
* Means collisions with container walls are less frequent
* The force of collisions is also reduced
* The strength of this reduction in frequency and force is
proportional to molar concentration, n/V
* Because both frequency and force are each reduced by a factor
proportional to n/V, the n/V term is squared
* The sign in front of this term is negative, since the attraction
reduces pressure
* π is the proportionality constant for this pressure reduction
van der Waals equation is based on the ideal gas
law but incorporates a correction for ________
and a correction for __________
pressure, volume
Note that the vdW equation does not perfectly
represent the behavior of real gases but it does
display __________
general behavior
Isotherms produced by vdW eqβn are same as ideal gas
law for _______ temperatures and low ________
high, molar volumes
Liquids and gases coexist when attractive and repulsive
effects are in _______
balance (related to vdW eq)
Can find the compression factor for critical points by plugging in the _________
critical constants
