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CH302: Chemistry > PHYSICAL EQUILIBRIA > Flashcards

PHYSICAL EQUILIBRIA Flashcards

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1
Q

What type of reaction occurs going up a phase transition graph?

A

Endothermic

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2
Q

What is dH of an endothermic reaction?

A

dH > 0

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3
Q

What is an endothermic reaction?

A

Endothermic reactions gain heat through abdorption

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4
Q

What type of reaction occurs going down a phase transition graph?

A

Exothermic?

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5
Q

What is dH of an exothermic reaction?

A

dH < 0

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6
Q

What is an exothermic reaction?

A

Exothermic reactions become cooler through the release of heat

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7
Q

What is dH and dS of condensation?

A

Gas → liquid

dH < 0 ; dS < 0

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8
Q

What is dH and dS of vaporization?

A

Liquid → gas

dH > 0 ; dS > 0

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9
Q

What is dH and dS of freezing?

A

Liquid → solid

dH < 0 ; dS < 0

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10
Q

What is dH and dS of fusion?

A

Solid → liquid

dH > 0 ; dS > 0

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11
Q

What is dH and dS of deposition?

A

Gas → solid

dH < 0 ; dS < 0

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12
Q

What is dH and dS of sublimation?

A

Solid → gas

dH > 0 ; dS > 0

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13
Q

In what order does enthalpy (S) increase?

A

S(s) < S(l) < S(aq) < S(g)

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14
Q

Why does enthalpy increase going up a phase transition graph?

A

Enthalpy increases as attractive interactions between molecules decreases

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15
Q

In what order does entropy (H) increase?

A

H(s) < H(l) < H(aq) < H(g)

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16
Q

Why does entropy increase going up a phase transition graph?

A

Because there are more potential microstates for distributing the energy

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17
Q

What controls the balance between entropy (H) and enthalpy (S)?

A

Temperature

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18
Q

Which dominates at a lower temperature?

A

Enthalpy (S)

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19
Q

Which dominantes at a higher temperature?

A

Entropy (H)

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20
Q

At any given temperature, the most stable substance has the lowest ______?

A

Free energy

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21
Q

What do straight lines indicate on a phase transition graph?

A

Straight lines indicate a phase change (dG = 0; equilibrium)

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22
Q

How does temperature stay constant during a phase change?

A

Energy is able to flow in and increase the potential energy due to the formation of a new state after the breaking of IMFs, and NOT increase the kinetic energy

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23
Q

What do slopes indicate on a phase transition graph?

A

Slopes indicate that there is no phase change

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24
Q

What happens when there is no phase change?

A

Temperature increases because energy flows into the system as heat

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25
Q

How is the slope on a phase transition graph related to heat capacity?

A

Slope is inversely related to heat capacity

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26
Q

What is a phase diagram?

A

Phase diagrams show regions of stability of different phases as a function of temperature and pressure

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27
Q

What is triple point?

A

triple point is where all 3 phases are at equilibrium (dG = 0)

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28
Q

What is critical point?

A

Critical point is where both the liquid and gas phases of a substance have the same density and are therefore indistinguishable

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29
Q

What is vapor pressure?

A

Vapor pressure is the partial pressure of a substance at equilibrium with a condensed phase (liquid/solid)

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30
Q

What happens to molecules in an open container?

A

They diffuse into the room and out of the atmosphere, and eventually all will evaporate

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31
Q

What happens to molecules in a closed container?

A

Those that evaporate will diffuse around in the gas phase, but some will collide with liquids

32
Q

What is the difference of kinetic energies between gas and liquid molecules?

A

Nothing, they have the same KEs because they share the same temperature

33
Q

How is vapor pressure related to boiling point?

A

Vapor pressure is inversely related to boiling point

34
Q

How is vapor pressure related to temperature?

A

Vapor pressure is directly related to temperature (exponentially)

35
Q

What is the Clausius-Clapeyron Equation?

A
36
Q

What is a solution?

A

A solution is a homogeneous mixture composed of a major component (solvent) and a minor component (solute)

37
Q

Why are the IMFs of the solvent very similar to the pure substance?

A

Because each solvent molecule is surrounded bu other solvent molecules

38
Q

Why are the IMFs of the solute very different to the pure substance?

A

Because the solute is completely surrounded by solvent

39
Q

What is dG in a mixture?

A

dG < 0

40
Q

Why is mixing 2 gases spontaneous?

A

Because either the enthalpy (S) goes down or entropy (H) goes up

41
Q

What is dS in a mixture?

A

dS > 0

42
Q

What is dH in a mixture?

A

dH is constant (dH = 0) because ideal gases have no IMFs, therefore no PE

43
Q

What is dH for a solution?

A
44
Q

How are interactions altered in a solution?

A

Solute-solute interactions are lost and solute-solvent interactions are gained

45
Q

What is dH lattice energy usually described as?

A

A positive number because energy is inputed to pull solutes apart

46
Q

What is dH solvation usually described as?

A

A negative number because E is released when the solute ineracts with the solvent

47
Q

When will a substance dissolve?

A

When a solution is formed, dH solutions > 0 and dS solutions > 0

However, like dissolved like to minimize dH solutions, where TdS solutions > dH solution

48
Q

What is Henry’s Law?

A

The mole fraction of the dissolved as in liquid is directly proportional to the pressure of the gas over the liquid; used to determine the solubility of a gas in a liquid

49
Q

When is a solution more stable?

A

A solution is more stable over a wider temperature range

50
Q

What are colligative properties?

A

Colligative properties are properties of a solution that depend on a particular solvent and the concentration, but they do not depend on the chemical nature of the solute

51
Q

What are the 4 colligative properties?

A
  1. Vapor pressure lowering
    1. VP solution < VP pure substance
  2. Boiling point elevation
    1. BP solution > BP pure substance
  3. Freezing point depression
    1. FP solution < FR pure substance
  4. Osmosis
    1. Solvent moves to solution side because it is lower in free energu
52
Q

What is the Van’t Hoff Factor (i) of a non-electrolyte (covalent bonds)?

A

1

53
Q

What is the Van’t Hoff Factor (i) of a strong electrolyte (salts)?

A

Number of ions in the formula

54
Q

What is the Van’t Hoff Factor (i) of a weak electrolyte?

A

More than 1 but less than 2

55
Q

What is the main effect of vapor pressure lowering?

A

Entropy (H)

dS solution > dS pure substance ; dG solution < dG pure solvent

56
Q

What is Raoult’s Law?

A

P° = VP of the pure solvent

Mole ratio = mole solvent / mole solution, where more moles of solute = smaller mole fraction = lower vapor pressure

57
Q

What is the formula used for boiling point elevation?

A

m = total solute concentration in molality (moles solute / kg solvent)

58
Q

What is the formula used for freezing point elevation?

A

m = (moles solute / kg solvent)

59
Q

What does an increase in solution concentration do to free energy?

A

Decreases dG

60
Q

What does an increase in solution pressure do to free energy?

A

Increases dG

61
Q

What triggers the end of osmosis?

A

When dG on both sides are equal

62
Q

How is osmotic pressure calculated?

A
63
Q

What happens when the solute is a salt in a spontaneous dissolution?

A

dH = dH LE + dH solvation, where…

  1. dH LE > 0 and dH solvation < 0, so dH solution ~0
  2. dG < 0 because spontaneous
  3. dS > 0 because solid → aqueous species
  4. An increase in T increases solubility
64
Q

What happens when the solute is a gas in a spontaneous dissolution?

A

dH solution = dH LE + dH solvation, where…

  1. dH LE = 0 and dH solvation < 0, so dH solution < 0
  2. dG <. 0 because spontaneous
  3. dS < 0 because gas → aqueous species
  4. An increase in temperature decreases solubility
65
Q

What happens when the solute is a liquid in a spontaneous dissolution?

A

dH solution = dH LE + dH solvation, where…

Like dissolves like (dH~0)

66
Q

What factors influence vapor pressure?

A

Temperature and identity

* Amount and volume don’t matter

67
Q

How are vapor pressure and IMFs related?

A

VP and IMFs are inversely related

68
Q

What do solid lines indicate on a phase diagram?

A

Similar free energies

69
Q

What is dH when solute-solvent IMFs are stronger?

A

dH > 0 (endothermic)

70
Q

What is dH when solute-solute IMFs are stronger?

A

dH < 0 (exothermic)

71
Q

What happens when a solution is made?

A
  1. Entropy (S) increases
  2. Free energy (G) decreases
  3. More stable than corresponding liquid
72
Q

How do you calculate molarity?

A

Molarity = moles solute / L solution

73
Q

How do you calculate molality?

A

Molality = moles solute / kg solvent

74
Q

How do you convert between molarity and molality?

A

Density

75
Q

What are freezing point and boiling point dependent on?

A

The total number of solute particles (concentration x # particles), NOT the identity

CH302: Chemistry (7 decks)

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