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MED 102- GENERAL CHEMISTRY > PARTIAL PRESSURES AND DALTON'S LAW > Flashcards

PARTIAL PRESSURES AND DALTON'S LAW Flashcards

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1
Q
  1. How do gases behave when in a mixture with other gases?
A
  • the individual pressures are all added to each other
  • this presents us with a total pressure
    ∴ P total = P1 + P2 + P3 …
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2
Q
  1. How do gases behave when they are mixed with other gases?
A
  • they behave as though they are alone
  • this is a result of the absence of interactions
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3
Q
  1. How is the concentration of any specific gas in a mixture worked out?
A
  • using the mole fraction (X)
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4
Q
  1. How would we calculate the pressure of the Earth’s Atmosphere?
A
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5
Q
  1. What is the Kinetic-Molecular Theory?
A
  • a gas consists of tiny particles
  • these particles are moving around randomly
  • the gas particles act independently of each other
  • there are no attractive or repulsive forces between
    them
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6
Q
  1. Within the Kinetic Molecular Theory of Gases, what kind of collisions are happening between gas particles?
A
  • elastic collisions
  • kinetic energy is conserved
  • momentum is conserved
  • kinetic energy is not lost
  • the kinetic energy is transferred
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7
Q
  1. Within Kinetic Molecular Theory, what is the average kinetic energy of gas particles proportional to?
A
  • the Kelvin Temperature

AVERAGE:
- not all the particles have the same speed
- speed goes to zero when particles collide
- this speed will stay at zero until something else
collides with the particles
- there is a disruption of speeds for given molecules

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8
Q
  1. What curve is seen in this diagram?
A
  • Boltzmann curve
  • these are the curves of different gases at constant
    temperatures
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9
Q
  1. What can be noticed in this curve?
A
  • the different molecules will move at different speeds
  • the temperature for all gases is constant and fixed
  • H2 has the highest average speed
  • this is because it has the lowest mass
  • light gases will move a faster speeds
  • kinetic energy is proportional to speed
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10
Q
  1. What do the letters of the equation represent?
A

u = average molecular speed
3RT = 3 x gas constant x Kelvin Temperature
M = mass of each molecule

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11
Q
  1. Where is the average speed of the gas particles situated?
A
  • the average speed of the gas particles is slightly to the
    right of the peak of the curve
  • the average speed depends on the mass of the gas
    particles
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12
Q
  1. What happens when the gas particles have an increased mass?
A
  • the the gas particles have a lower average sped
  • Oxygen is the heaviest molecule
  • this is why it has the lowest average speed
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13
Q
  1. How can we relate Boyle’s Law to the Kinetic Molecular Theory to explain Gas Behaviour?
A

IF WE REDUCE THE VOLUME:
- the particles will collide
more frequently with the
walls
- this will increase the
pressure
- this is because the pressure
depends on the frequency
and the intensity of the
collisions

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14
Q
  1. How can we relate Charles’ Law to the Kinetic Molecular Theory to explain Gas Behaviour?
A

WHEN THE TEMPERATURE INCREASES:
- the kinetic energy of the
particles increases
- the particles are now moving
faster

IN ORDER TO MAINTAIN CONSTANT PRESSURE:
- which is a requirement for
Charles’ Law
- the container size needs to
expand
- this will increase the volume
- the particles will be hitting the
walls with a higher intensity
- the expanded volume
decreases the frequency of the
collisions
- this keeps the pressure
constant

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15
Q
  1. How can we relate Avogadro’s Law to the Kinetic Molecular Theory to explain Gas Behaviours?
A

THE AMOUNT OF GAS INCREASES:
- the collisions with the wall tend to become more
frequent
- the container must expand
- this lowers the frequency of the collisions
- this maintains the pressure constant
- constant pressure is necessary for Avogadro’s Law

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16
Q
  1. What is Diffusion?
A
  • this is the process by which two different gases mix
    together
  • this is done by random molecular motion with
    frequent collisions
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17
Q
  1. What is going on the diagram?
A
  • the Hydrogen particles are diffusing faster
  • this is because they are smaller
  • these particles have a lower molecular mass
18
Q
  1. How is Entropy present in the last step of the diagram?
A
  • the particles are more disordered
  • this is because there is a natural tendency for things
    to become more disordered
  • nature detests order
19
Q
  1. What is Effusion?
A
  • this is the process by which gas escapes through a
    pinhole
  • this leads to a vacuum
  • or into a region of lower pressure
20
Q
  1. What does Graham’s Law mathematically state?
A
  • the rate of effusion or diffusion is inversely
    proportional to the square root of the mass
    of the substance
21
Q
  1. How would we mathematically figure out the
    relation between the rates and the masses of two
    different gases?
A
  • the gas with the lowest mass escapes more easily
  • the gas with the highest mass escapes with more
    difficulty
22
Q

22: The molecular mass of the Ammonia is
17g/mol.
: The molecular mass of the HCl is 36.5 g/mol
∴Which has diffuses faster?

A
  • Ammonia
  • this is a direct result of its lighter gas particles
23
Q

23: The molecular mass of the Ammonia is
17g/mol.
: The molecular mass of the HCl is 36.5 g/mol
∴What is seen on the left hand side of the tube?

A
  • a cotton ball dipped in NH4OH (aq) solution
  • this will give off NH3 gas particles

NH3 = Ammonia

24
Q

24: The molecular mass of the Ammonia is
17g/mol.
: The molecular mass of the HCl is 36.5 g/mol
∴What is seen on the right hand side of the tube?

A
  • a cotton ball dipped in Hydrochloric Acid (HCl)
  • the cotton ball will off HCl particles
25
Q

25: The molecular mass of the Ammonia is
17g/mol.
: The molecular mass of the HCl is 36.5 g/mol
∴What happens within the tube when the NH3
and the HCL particles diffuse?

A
  • the NH3 particles start moving to the right
  • the HCL particles start moving to the left
  • the lighter NH3 particles move much faster
26
Q

26: The molecular mass of the Ammonia is
17g/mol.
: The molecular mass of the HCl is 36.5 g/mol
∴What happens within the tube when the NH3
and the HCL particles meet?

A
  • they form a white smoke
  • this smoke is made of NH4Cl
  • the white smoke will form to the right of the middle of
    the tube
27
Q
  1. What does the Ideal Gas Law require to work?
A
  • large distances between the gas particles
28
Q
  1. When does the Ideal Gas Law fail?
A
  • when the gas particles get too close together
  • this lack of space allows there to be interactions
    between the particles
  • this will happen at a high pressure
  • and a low temperature

THE IDEAL GAS LAW WILL ALSO FAIL WHEN:
- the size of the gas particles becomes very large
- this assumes that the gas particles are points with no
volume

29
Q
  1. What two factors become important when there is a close contact of Gas Particles?
A
  • finite volume of the gas
  • intermolecular attractive forces
30
Q
  1. Which equation describes Real Gas Behaviour?
A
  • the Van Der Waals Equation
31
Q
  1. What is the Van Der Waals Equation?
A
  • nb = the bigger the molecule
    = the bigger the volume concentration
  • an² = this is related to the intermolecular forces that
    exist between gas molecules
32
Q
  1. What does this table describe?
A
  • this table consists of ‘a’ and ‘b’ factors
  • these are found in the Van Der Waals equations for
    real gases
33
Q
  1. What does the constant ‘a’ relate to?
A
  • it relates to the magnitude of intermolecular forces
    within the molecule
34
Q
  1. Which molecules have a large ‘a’ constant?
A
  1. Heavy CCl4
    • this has large London Dispersion Forces
  2. Water Molecule
    • it has hydrogen bonds
35
Q
  1. Which molecules have a large ‘a’ constant?
A
  1. Heavy CCl4
    • this has large London Dispersion Forces
  2. Water Molecule
    • it has hydrogen bonds
36
Q
  1. What is the constant ‘b’ related to?
A
  • it is related to the size of the molecule
37
Q
  1. Which molecule has the largest ‘b’ constant?
A
  • CCl4
  • it is the largest molecule
38
Q
  1. Which molecule has the smallest ‘b’ constant?
A
  • He
  • it is the smallest molecule
39
Q
  1. What happens when the molecule is heavier and polar?
A

THE HEAVIER THE MOLECULE:
- the more electrons are present
- the more Inter molecular forces are present

POLAR MOLECULES:
- have more inter molecular forces

40
Q
  1. Answer this question?
A

E.
- the smallest ‘b’ constant will belong to the smallest
sized molecule
- this is H2

41
Q
  1. Read through the summary.
    Does this make sense?
A
  • yes

MED 102- GENERAL CHEMISTRY (27 decks)

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