gases Flashcards

1
Q

Kinetic-Molecular Theory (KMT) of Gases Based on what three assumptions?

A
  1. The gas consists of molecules of mass in ceaseless random motion, obeying the laws of classical mechanics
    – Particles move at constant velocity in straight lines between collisions (with other particles or container)
  2. The size of the molecules is negligible (their diameters are much smaller than the average distance travelled between collisions)
  3. Molecules interact only through brief elastic collisions
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2
Q

RMS speed of the gas depends on the ______ of the gas, M, and the gas’s temperature (k)

A

molar mass

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3
Q

_____ is one number that describes the speed of
molecules with given molar mass and temperature

A

π‘£π‘Ÿπ‘šπ‘ 

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4
Q

For _____ temperatures and large masses, low speeds
predominate

A

low

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5
Q

For ____ temperatures and small masses, the
distribution spreads out toward higher speeds

A

high

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6
Q

If we know the average speeds of particles, we can figure out the average speed with which they
collide, called the _________

A

mean relative speed

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7
Q

At constant V, Since π‘£π‘Ÿπ‘’π‘™ ∝ π‘£π‘šπ‘’π‘Žπ‘› ∝ π‘£π‘Ÿπ‘šπ‘  ∝ 𝑇, collision frequency _______ with temperature

A

increases

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8
Q

At constant T, the collision frequency is __________ to pressure

A

directly proportional

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9
Q

At constant T, increasing N or decreasing V would ________ pressure, which would increase collision frequency

A

increase

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10
Q

Collision frequency _______ with increasing T because the particles are moving faster

A

increases

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11
Q

Collision frequency _________ with P because the particles are closer together and don’t need to move as far in order
to collide, thus causing more frequent collisions

A

increases

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12
Q

If n is increased, P will ________ without changing T

A

increase

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13
Q

If T is fixed but P goes up, πœ† will go down. P and πœ†
are _______ proportional

A

Inversely

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14
Q

πœ† is ___________ of T

A

independent

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15
Q

We know the ideal gas law is an approximation
that pretends that what?

A

1) gas particles do not interact except during collisions

2) gas particles
themselves have no volume

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16
Q

Real gases behave most ideally when P is very _____
and/or T is very high

A

low

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17
Q

When T is ______ (close to condensation) or P is high, gas behavior deviates significantly from ideality

A

low

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18
Q

When gas particles are very close, they _____ each
other

A

repel

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19
Q

When gas
particles are
close, but not
very close,
they ________
each other

A

attract

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20
Q

Ideal gas particles, with no attractive interactions, would never form a ________ or solid

21
Q

Real gases

A
  • Particles actually attract one another
    – Particles have non-neglible volume
22
Q

At large V and high T, the isotherms for real gases
are very similar to those of i____________

A

deal gases

23
Q

One correction is in terms of the volume (related to virial equation of state)

A

– Ideal gas law assumes particles occupy no volume
– vdW equation says particles do occupy volume, which
reduces the free volume particles can travel through
– b is the excluded volume per mole, so the free volume
becomes 𝑉 βˆ’ 𝑛𝑏

24
Q

What does PEMDAS mean?

A
  1. Parentheses
  2. Exponentiation
  3. Multiplication
  4. Division
  5. Addition
  6. Subtraction
25
The atom is an __________, spherical entity composed of a positively charged central nucleus surrounded by one or more negatively charged electrons.
electrically neutral
26
The atomic nucleus consists of ________ and neutrons.
protons
27
Charge
– Proton (+) and electron (–) have equal but opposite charges – Neutron is electrically neutral (no charge)
28
Mass
– Proton and neutron have very similar masses – Electron has much smaller mass than proton or neutron
29
Location
– Proton and neutron are in the nucleus – Electrons are found outside the nucleus
30
Atomic number (Z)
Number of protons in an atom’s nucleus
31
Each element has a ________ atomic number
unique
32
Atoms are neutral, so number of electrons is what?
equal to atomic number
33
Mass number (A)
Sum of protons and neutrons in an atom’s nucleus
34
________ are atoms of a given element with the same number of protons, but a different number of neutrons.
Isotopes
35
Isotopes have the same atomic number, but a different _________
mass number
36
Atomic mass is a weighted average of the mass numbers of ____________
all isotopes
37
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
38
If T is fixed but P goes up, mean free path (πœ†) will go __________
down
39
To quantify the reduced pressure exerted by real gases we the _______
compression factor ( 𝑍 = π‘‰π‘š/ 𝑉'π‘š) (Where π‘‰π‘š is the molar volume (V/n) and π‘‰π‘šΒ° is the molar volume of an ideal gas at same T and P)
40
Using the Ideal gas law, what is another way to write the compression factor?
𝑍 = π‘ƒπ‘‰π‘š/ 𝑅𝑇 (or π‘ƒπ‘‰π‘š = 𝑅𝑇𝑍)
41
What are the two ways of expressing the virial equation of state?
1. π‘ƒπ‘‰π‘š = 𝑅𝑇 1 + 𝐡′𝑃 + 𝐢′𝑃2 + β‹―) 2. π‘ƒπ‘‰π‘š = 𝑅𝑇 ( 1 + 𝐡/π‘‰π‘š + 𝐢/𝑉^2π‘š+ β‹―)
42
The van der waals equation corrects the ideal gas law to replicate gas __________
behavior
43
What is the first correction the van der waals equation makes?
1. is in terms of the volume – Ideal gas law assumes particles occupy no volume – vdW equation says particles do occupy volume, which reduces the free volume particles can travel through – b is the excluded volume per mole, so the free volume becomes 𝑉 βˆ’ 𝑛𝑏
44
What is the second correction the van der waals equation makes?
is in terms of the pressure – Ideal gas law assumes particles don’t interact – 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‘Ž is the proportionality constant for this pressure reduction
45
van der Waals equation is based on the ideal gas law but incorporates a correction for ________ and a correction for __________
pressure, volume
46
Note that the vdW equation does not perfectly represent the behavior of real gases but it does display __________
general behavior
47
Isotherms produced by vdW eq’n are same as ideal gas law for _______ temperatures and low ________
high, molar volumes
48
Liquids and gases coexist when attractive and repulsive effects are in _______
balance (related to vdW eq)
49
Can find the compression factor for critical points by plugging in the _________
critical constants