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CH 302 > Unit 1 > Flashcards

Unit 1 Flashcards

1
Q

Same molec
Same T
Different V
VP?

A

Same VP

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2
Q

Same molec
Diff Temp
VP?

A

Higher temp -> higher KE -> more molec in gas phase -> higher VP

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3
Q

Which molecule would you expect to have a lower H(l) at room temperature?
A. H2CO
B. CH3OH

A

Lower H(l) -> most stable -> the one with H bonding
Strong IMF -> most stable -> lowest E and lowest H(l)
Answer: B

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4
Q

Which molecule would you expect to have a lower H(g) at room temperature?
A. H2CO
B. CH3OH

A

Lower H(g) -> most stable -> IMF
Ideal gas -> no IMF
Answer: same

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5
Q

🔺S equation

A

🔺S = qrev/T = 🔺H/T

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6
Q

Which molecule would you expect to have a higher S(g) at room temperature?
A. H2CO
B. CH3OH

A 
Higher S(g) -> more molec in gas phase -> weaker IMF
Answer: A
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7
Q

🔺G° equation

A

🔺G° = 🔺H° - T🔺S°

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8
Q

What is 🔺G and 🔺Suniv for a spontaneous process?

A

Favored
Spontaneous -> 🔺G = negative
🔺Suniv = positive

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9
Q

What is 🔺G and 🔺Suniv for a nonspontenous process?

A

“Uphill”
🔺G = positive
🔺Suniv = negative

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10
Q

Does breaking IMFs require energy or release energy? Endo or exo? Sign of 🔺H? Examples?

A

Requires energy
Endo
🔺H = positive
Ex. Vaporization (l -> g), fusion (s -> l), sublimation (s -> g)

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11
Q

Does forming IMFs require energy or release energy? Endo or exo? Sign of 🔺H? Examples?

A

Releases energy
Exo
🔺H = negative
Ex. Condensation (g -> l), freezing (l -> s), deposition (g -> s)

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12
Q

At equilibrium, 🔺G = ? Greactants = ?

A 
🔺G = 0
Greactants = Gproducts
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13
Q

MP/FP equation

A

T = 🔺Hfus / 🔺Sfus

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14
Q

Boiling point definition

A

When VP = the current atmospheric pressure -> liquid boils

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15
Q

Normal boiling point definition

A

Boiling point at atmospheric pressure (1 atm)

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16
Q

What will be the boiling point of water in Denver? Assume the atmospheric pressure is 0.82 atm.
A. >100 °C
B. <100 °C
C. 100 °C

A

0.82 atm -> not as many molecules in the gas phase
Patm ⬇️, Tbp⬇️
BP ⬇️
Answer: B

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17
Q

What’s the difference between boiling point and evaporation?

A

BP specific @ P

Evaporation -> room temp -> min KE needed to break IMF

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18
Q

Partial pressure equation

A

PV = nRT

* PA = nRT / V *

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19
Q

BP equation

A

T = 🔺Hvap / 🔺S

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20
Q

Which of the below substances would you expect to have the largest value for 🔺Hvap?
A. Methane
B. Water
C. Acetone

A

B

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21
Q

Clausius-Clapeyron Equation

A 
ln(P2/P1) = 🔺Hvap/R (1/T1 - 1/T2)
1 molec. 2 temps
🔺Hvap -> J/mol
R -> 8.314 J/mol•K
T -> K
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22
Q

Warming solid/liquid/gas equation

A

q = mC🔺T

Comes out in J or kJ

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23
Q

Phase change equation

A

Melting solid -> q = n🔺Hfus
Boiling liquid -> q = n🔺Hvap
Comes out in J or kJ

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24
Q

For a phase change, we assume that 🔺T=? 🔺G=?

A

🔺T=0
🔺G=0
Equilibrium

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25
Q

Triple point definition

A

All 3 phases exist at this T & P

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26
Q

Critical point definition

A

The T & P limits for gas/liquid phases

Cannot distinguish gas/liquid above critical

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27
Q

If there is a positive slope, can you melt dry ice by applying a higher pressure? Is the solid or liquid more dense?

A

No

The solid

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28
Q

If there is a negative slope, can you melt ice by applying a higher pressure? Is the solid or liquid more dense?

A

Yes

The liquid

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29
Q

🔺Hsolution equation

A

🔺Hsolution = 🔺HLE + 🔺Hsolvation

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30
Q

Is dissolution for a solid solute endothermic or exothermic? Why?

A 
Endothermic
🔺Hsolution = 🔺HLE + 🔺Hsolvation
Positive = positive + negative
🔺HLE > 🔺Hsolvation
Solute bonds > solvent bonds
Ionic/ ion-ion bonds > H bonds
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31
Q

What is the sign of 🔺Ssolution when we dissolve a solid solute in a liquid solvent?

A

🔺Ssolution = positive

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32
Q

What will happen to a supersaturated aqueous sodium chloride solution when the temperature is increased?
A. No change.
B. The solubility will increase
C. The solubility will decrease

A 
Solid solute
⬆️ T, ⬆️ KE
⬆️ solubility
Breaking the solute-solute bonds in the lattice
Answer: B
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33
Q

Is dissolution for a gaseous solute endothermic or exothermic? Why?

A

Exothermic
🔺Hsolution = 🔺HLE + 🔺Hsolvation
Negative = 0 + negative
No LE for gas solute

34
Q

What is the sign of 🔺Ssolution when we dissolve a gaseous solute in a liquid solvent?

A

🔺Ssolution = negative

35
Q

What will happen to a carbonated soda when the temperature is increased?
A. No change
B. The solubility will increase
C. The solubility will decrease

A 
Gas solute
⬆️ T, ⬆️ KE
⬇️ solubility
Break solute-solvent bonds (IMFs)
Answer: C
36
Q

Henry’s Law equations

A

Cgas = kH * Pgas
kH -> Henry’s constant [M/atm]
Pgas = K * Xgas
Xgas = # mol A / tot mol

37
Q

Strong electrolyte definition

A

100% dissociation
AB -> A + B
Ionic = strong

38
Q

Weak electrolyte definition

A

<100% dissociation

AB -> A + B, AB

39
Q

Nonelectrolyte definition

A

0% dissociation
AB -> AB
Covalent, i = 1

40
Q

How to calculate van’t Hoff factor

A

i = moles of particles in solution / moles of formula units dissolved

41
Q

Molarity equation

A

M = moles solute / L solution

42
Q

What does “concentration of particles” mean?

A

Molarity with the van’t Hoff factor -> iM = i(moles solute) / L solution

43
Q

Molality equation

A

♍️ = moles of solute / kg solvent

44
Q

Molality of the particles of a solution equation

A

♍️ = (i) mol solute / kg solvent

45
Q

What is the effect of ⬆️ mixing?

A

⬆️ mixing, ⬆️ S, ⬇️ G, more stable, ⬇️ VP, ⬆️ BP

46
Q

Gsolvent ? Gsolution

Ssolvent ? Ssolution

A

Gsolvent > Gsolution

Ssolvent < Ssolution

47
Q

Raoult’s Law for VPsolution

A

VPsolution = Xsolvent * VPsolvent
Xsolvent = # moles solvent / tot moles
VPsolvent -> p°

48
Q

Raoult’s Law for 🔺VP

A 
🔺VP = -Xsolute * VPsolvent
Xsolute = mol solute / tot moles
Xsolute -> watch for i!
VPsolvent-> VP°
* VPsolution = VP°solvent + 🔺VP *
49
Q

What is Xsolute for 1 mole of sodium chloride in 55.55 mol H2O?

A

X = mol solute / tot mol = 1 mol Na+ + 1 mol Cl- / (55.55 + 1 + 1) = 0.035

50
Q

Raoult’s Law (for liquids)

A

VPsolution = VPsolvent A + VPsolvent B

51
Q

Dalton’s Law (for gases)

A

Ptotal = PGas A + PGas B

52
Q

Sample A: 250 mL of water
Sample B: 1 mole of sugar in 250 mL of water
Which sample has the highest boiling point? Why?

A

B
IMFs
solute-solvent

53
Q

Boiling Point Elevation equation

A 
🔺Tb = iKb♍️
🔺BP = iKb♍️
🔺BP -> °C
Kb = BP elevation constant [°C/♍️]
♍️ -> molal
Tbp’ = Tbp° + 🔺Tbp
BP’ = BP° + 🔺BP
54
Q

Nonvolatile solute van’t hoff factor

A

1

55
Q

Sample A: 250 mL of water
Sample B: 1 mole of sugar in 250 mL of water
Which sample has the lowest freezing point? Why?

A

B

Solution is more stable over a wider Temp range

56
Q

Freezing Point Depression equation

A 
🔺Tf = -iKf♍️
FP = -iKf♍️
FP -> °C
Kf = FP depression constant [°C/♍️]
FP’ = FP° + 🔺Tf
57
Q

If there are 0.0719 mol NaCl, how many mol solute are there?

A

mol solute = 0.0719 mol Na+ + 0.0719 mol Cl- = 0.1438 mol

58
Q

You find a U tube that has allowed for the solvent to pass through the barrier after a period of time. A is lower and B is higher.

  1. Is A the solvent or the solution?
  2. Is B the solvent or the solution?
  3. Why?
A
  1. Solvent
  2. Solution
  3. Solvent moves to solution to try to establish equilibrium
59
Q

Osmotic Pressure equation

A 
pi = iMRT
pi -> atm
M -> molarity
ionic -> iM
R = 0.08206 L•atm / mol•K
T -> Kelvin
60
Q

Magnitude of Q or K Very Small
Reaction Progression?
Spontaneity?

A

Reactant Favored

nonspon

61
Q

Magnitude of Q or K 1-ish

Reaction Progression?

A

[Products] = [Reactants]

62
Q

Magnitude of Q or K Very Large
Reaction Progression?
Spontaneity?

A

Product Favored

spon

63
Q

KC vs. KP equation

A 
KP = KC(RT)^🔺n
R -> 0.08206 L•atm / mol•K
T -> Kelvin
🔺n = products - reactants
gases only!
64
Q

Product Favored Reaction

A

Product Favored -> Exo

G° products is lower than G° reactants

65
Q

Reactant Favored Reaction

A

Reactant Favored -> Endo

G° reactants is lower than G° products

66
Q

How to find 🔺G° on free energy diagram

A

Right side of curve - left side of curve

Low right side - high left side = negative (spon)

High right side - low left side = positive (nonspon)

67
Q

Which side of the curve is Q < K?

A

Left side is always Q < K

68
Q

🔺G° vs. 🔺G equation

A 
🔺G = 🔺G° + RTlnQ
RTlnQ -> mixing -> S
🔺G = standard + mixing
(real)
expt
69
Q

🔺G° equation at equilibrium

A 
🔺G = 0
Q = K
🔺G° = -RTlnK
R = 8.314 J / mol•K
T = 298 K
70
Q

When K is small, what is the sign of 🔺G°?

A

Positive

71
Q

When K is big, what is the sign of 🔺G°?

A

Negative

72
Q

What happens when I increase the reactants?

A

⬆️ Reactant, ⬇️ Q, shift to make more products
Reactant —> Product
want: Q=K
“Add Away”

73
Q

What happens when I decrease the reactants?

A

⬇️ Reactants, ⬆️ Q
Q > K
React ⬅️⬅️ Prod
“Take Toward”

74
Q

Where does the reaction shift when heat energy is added to an exothermic reaction?

A 
Reactants -> Products + Heat
⬆️ Prod, ⬆️ Q
Q > K
⬅️⬅️
The reaction shifts to “add” some reactants.
75
Q

Where does the reaction shift when heat energy is added to an endothermic reaction?

A 
Reactants + Heat -> Products
⬆️ React, ⬇️ Q
Q < K
➡️➡️
The reaction shifts to “add” some products.
76
Q

van’t Hoff Equation

A 
ln(K2/K1) = (🔺H°/R) * (1/T1 - 1/T2)
K -> eq constants
🔺H° -> J/mol
R -> 8.314 J/mol•K
T -> Kelvin
77
Q

Where does the reaction shift when we decrease the volume of the container of gases?

A

⬇️ V, ⬆️ P, P is too high
The reaction will shift in such a way to decrease the pressure.
It will move towards the side of the reaction with fewer gas molecules. -> wants to remove gas particles in order to ⬇️ P

78
Q

Where does the reaction shift when we increase the volume of the container of gases?

A

⬆️ V, ⬇️ P, P is too low
The reaction will shift in such a way to increase the pressure.
It will move towards the side of the reaction with the greater number of gas molecules.
want more gas particles

79
Q

How does decreasing the temperature of an exothermic reaction affect the value of K?

A

K will increase

80
Q

How does increasing the temperature of an endothermic reaction affect the value of K?

A

K will increase

81
Q

How does increasing the temperature of an exothermic reaction affect the value of K?

A

K will decrease

82
Q

How does decreasing the temperature of an endothermic reaction affect the value of K?

A

K will decrease

CH 302 (5 decks)

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