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CHEM1602 > Section C > Flashcards

Section C Flashcards

1
Q

6 exaples of Energy usage

A

Synthesis of cellular macromolecules

synthesis of membranes, phospholipids and metabolites

cellular movements

transport of molecules against concentration gradient

generation of an electrical potential across membrane

heat

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2
Q

Energy from the sun, photons:

E = ….

A

E = hv

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3
Q

Problem z secton C “manifestations of energy”

A

s

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4
Q

Problem z secton C “manifestations of energy”

A

s

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5
Q

1 cal -

A

energy required to increase temperature of 1g water by 1Celcius

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6
Q

1 cal =

A

4.2 J

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7
Q

How can you measure energy changes?

A

Exploit the equivalence of energy forms and convert energy into a temperature rise or melt a standard quantity of ice

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8
Q

Specific Heat capacity:

A

The energy (enthalpy) change in Joules required to raise the temperature of 1 kg of material by 1 Celcius or 1 Kelvin

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9
Q

“Latent heat” (Enthalpy of fusion/melting):

A

The energy (enthalpy) change in Joules required to convert 1 kg of material from solid to liquid at the same temperature.

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10
Q

The heat capacity is an extremely valuable quantity that depends on ….

A

both inter- and intra- molecular parameters - it is the gradient of a plot of “energy” vs temperature.

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11
Q

Energy changes can be measured using …

A

a calorimeter

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12
Q

calorimeter -

A

an insulated device in which the temperature change associated with a specific chemical or physical change can be measured. The device is normally calibrated electrically.

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13
Q

The universe -

A

this is the big picture, both the system and the surroundings

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14
Q

The system -

A

the chemical reactions or mechanism under consideration i.e. a test tube and its contents.

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15
Q

Systems may be:

A

Open
Closed
Isolated

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16
Q

Open system -

A

the system may exchange energy and matter with the surroundings (e.g. a person)

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17
Q

Closed system -

A

the system may exchange energy (esp “heat”) with the surroundings but not matter (e.g. planet Earth?)

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18
Q

Isolated -

A

no exchange can occur (e.g. the contents of a sealed vacuum flask)

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19
Q

The surroundings -

A

Everything around the system that has physical contact with it and may or may not exchange “heat” and matter with it.

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20
Q

Biological systems are …. systems
1.
2.

A

open

  1. Plants take photons from the sun, minerals, water from roots, and CO2, from the atmosphere
  2. Animals exchange matter by eating, breathing, excreting, pooping. They also exchange energy by the same routes.
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21
Q

Przypomnienie:

A

It can be tricky to define the system and distinguish it from the surroundings.

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22
Q

Activity: In bed awake
Energy conversion rate / W: 90

Activity: Reading
Energy conversion rate / W: 120

Activity: Working at computer
Energy conversion rate / W: 160

Activity: Walking
Energy conversion rate / W: 200

Activity: Having Sex (“energetic”)
Energy conversion rate / W: 350

Activity: Cycling hard uphill
Energy conversion rate / W: 350

Activity: Rowing at max effort
Energy conversion rate / W: 1000

A

k

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23
Q

Kinetic energy:

A
  • Heat or thermal energy (motion of molecules)
  • Radiant energy (photons)
  • Electrical energy (ion flows)
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24
Q

Potential energy:

A
  • Bond energy (chemical species)
  • Chemical energy (concentration differences)
  • Electrical energy (ion gradients)
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25
Q

The Maxwell-Boltzmann Distribution -

A

Thermal (molecular motional) Energy

Distribution is unsymmetrical weighted towards lower speeds

As temperature rises, curbe flattens and moves to the right.

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26
Q

Temperature relates to …….. which is described by…..

A

the distribution of thermal energy

the Bolttzmann distribution function

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27
Q

As temperature increases occupancy of higher energy levels …

A

increases

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28
Q

Problem: Given that a peptide can adobt two conformations separated by 5.9 kJ mol^-1, what will be their relative proportions at a temperature of 37 Celcius?

A

Ans. ~10:1

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29
Q

The First Law -

A

The Internal Energy

30
Q

The internal energy … is the ….

A

U
the sum of all possible energies in the system i.e. thermal (translational, rotational and vibrational) energies, bond energy, intermolecular energies.

31
Q

The absolute value of U …

A

CANNOT BE DETERMINED

32
Q

Extensive property -

A

U is an extensive property- it depends on the amount of material you have (the internal energy of two Mars bars is twice that of one Mars bar)

33
Q

Internal energy can be changed by transferring energy in or out of the system

A

do poprawy

34
Q

State Function -

A

U is a state Function - its values is independent of how you arrive at that particular value - it is path indepentent. You could go from state 1 to state 2 by heating, by doing work, or by combination of the two - the final value of U will not be affected (cf. altitude). State functions are usually represented by capital letters.

35
Q

The Zeroth Law of Thermodynamics

A

Energy flows (i.e. “heat”) between objects such as to equalize their temperatures

36
Q

0th Law of Thermodynamics -> Temperature is therefore the equivalent of ….

A

pressure - it tells us in which direction thermal energy will flow

37
Q

Przypomnienie:

A

Notice that temperature is an intensive property of the system - it is not additive and does not depend on the amount of material (if I have two glasses of water at 5 Celcius, if I mix them together the temperature is unaffected by the amount of water I have).

38
Q

Altitude is

A

another state function. Depends only on where you start and where you finish - not on path.

39
Q

Heat -

A

the transfer of energy due to a difference in temperature between the system and surrounds. It results in a change in the random motion at atomic/molecular level in the system and surroundings.

40
Q

Work -

A

the transfer of energy to or from the system that results in a coherent/coordinated motions of the molecules of a system.

41
Q

Heat or work? Can you tell one is which?

  1. Ringing a bell
  2. Hearing a sound
  3. The Na/J ATPase moving Na+ ions across a membrane
  4. Ions moving a channel in a membrane down a gradient
  5. Warming a cup of tea with an electric blender.
  6. Warming a cup of tea with a candle.
  7. Contracting a muscle fibre
  8. Lifting a weight through a certain distance.
  9. Letting a weight fall on the floor.
  10. Adding an ice cube to a glass of water.
  11. Contracting a rubber band using a candle flame
A 
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
42
Q

Przypomnienie: Heat is NOT ….

A

a form of energy. This is a common mistake- what we think of as heat is actually the transfer of energy from a hotter object to a colder one.

43
Q

Calculate the work done by a cyclist (60 kg) climbing the Alpe d’Huez (vertical climb 1200 m). Is this her total energy expenditure?

A

Ans. ~700 kJ

Assuming the climb took 40 mins, what is the cyclist’s power output? Is this estimate realistic.

44
Q

.Work is maximized if changes are reversible

this only happens if …

A

work is done in infinitesimal steps

45
Q

It is not possible to measure …

A

the absolute enthalpy H (enthalpy) of a substance, only differences

46
Q

Przypomnienie:
H is normally referenced to a particular set of conditions - 1 mole of pure substance at 298.15 K,
1 bar (0.986 932 atm)

A

h

47
Q

Przypomnienie:
Bond enthalpies vary as a function of the other groups in the molecule so the bond C–H bond energy changes from methane, ethane, benzene, glucose etc.

A

h

48
Q

Mean bond enthalpies -

A

allow you to predict formation enthalpies for molecules, or

even enthalpies of reaction.

49
Q

Przypomnienie:
Additional quantity ENTROPY that gives direction of spontaneous change.
Entropy is a STATE FUNCTION.

A

h

50
Q

The Second Law of Thermodynamics:

A

“In any spontaneous process the entropy increases.”
“Over time the entropy of the universe increases.”

ΔSTOTAL = ΔSUNIVERSE > 0

51
Q

The Second Law of Thermodynamics:

A

“In any spontaneous process the entropy increases.”
“Over time the entropy of the universe increases.”

ΔS total = ΔS universe > 0

52
Q

The Third Law of Thermodynamics:

A

For any perfect crystal, at T = 0 K, the entropy is zero.

It is therefore possible to determine the molar entropy of any substance under standard conditions - all we need to do is to measure the molar heat capacity C as a function of temperature

Rules of thumb: Molar entropies: Gas&raquo_space; Liquid > Solid ; Entropy increases with degrees of freedom and
molecular size

53
Q

The Gibbs Energy equation:

co gdy pierwsza value =, > or

A

ΔG = ΔH − TΔS

If ΔG > 0 then the reaction is uphill or
endergonic
If ΔG

54
Q

`What is The Gibbs Energy?

A

The Gibbs energy is the energy from a change in the system that will be available to do useful non-pV work (e.g. moving ions or molecules around, building other molecules, etc)

Gibbs energy requires p and T to be fixed.

55
Q

ΔH > 0
(positive)

ΔS> 0
(positive)

A

ΔG
Reaction will not be spontaneous at low temperature but above a critical temperature will switch over to spontaneous behaviour

CaCO3 ⇔ CaO + CO2

56
Q

ΔH > 0
(positive)

ΔS

A

ΔG
The reverse reaction will be spontaneous at all
temperatures.

6CO2 + 6H2O ⇔C6H12O6 + 6O2

57
Q

ΔH

A

ΔG
The reaction will be spontaneous at low temperatures but above a critical temperature the reverse reaction will be favoured.

NH3 + HCl ⇔ NH4Cl

58
Q

The Gibbs Energy and Self-Assembly

explain why does non polar molecule assemble?

Therefore, Formation of organized structures is
….. effecty.

A

Taking a non-polar molecule and surrounding it by water
requires water to be separated and rearranged to
make a solvent cage.

This is a somewhat exothermic process especially if you
have a polar head group: ΔH

59
Q

The Gibbs Energy and Self-Assembly

explain why does non polar molecule assemble?

Therefore, Formation of organized structures is
….. effecty.

A

Taking a non-polar molecule and surrounding it by water
requires water to be separated and rearranged to
make a solvent cage.

This is a somewhat exothermic process especially if you
have a polar head group: ΔH

60
Q

Rozwiąż poniższe zadania:
1. Calculate the energy transfer required to prepare the water required for a cup of tea. Is this heat or work?
2. Calculate the power output (in Watts) of an adult human. Assume an adult requires 2500 kcal/day.
3. Assuming no losses, how hot would 10 litres of water get using 2500 kcal/day.
4. Could you heat water to this temperature by sitting in the bath (assuming the bathtub were perfectly insulated).
5. How fast are the electrons moving if we apply a potential of 10 kV?
6. Given molecules with two energy levels separated by an energy difference of 5 kJ mol-1 , what percentage of
molecules are in the upper state at –200 °C and + 200 °C?
7. What would you predict to be the temperature difference between the top and the bottom of a waterfall 200 m high?
8. Imagine shaking a thermos flask full of cream full of cream? What happens? Is there a change in internal energy?
What was the mechanism of any change in the internal energy?
9. A piece of sodium is dropped into water. What happens? Can you express this in terms of q, w, U and H? (Don’t worry
about the precise numbers - think signs)
10. What is the enthalpy of formation of methane, CH4?
ΔHcomb
Θ(H2) = –285.6 kJ mol–1;
ΔHcomb
Θ(Graphite) = –393.1 kJ mol–1
ΔHcomb
Θ(Methane) = –889.4 kJ mol–1
11. Estimate the the standard enthalpy change for the reaction H2O2 (l) → 2H2O (l) + O2(g). ΔHvap (H2O2) = 51.6 kJ mol-1;
ΔHvap (H2O) = 44 kJ mol-1.
12. Lysozyme denatures at 75.5 °C and the enthalpy of unfolding ΔHunf = 509 kJ mol-1. What is the entropy change, ΔS of
the transition?
13. What is the maximum efficiency of a power station operating at 200, 400 and 600 °C.
14. Adenosine triphosphate (ATP) can be hydrolysed to release its phosphate group. At the “physiological”, temperature
36 °C (pH7) it has been estimated that ΔH = -20.08 kJmol-1 and ΔS = + 35.21 JK-1mol-1., Estimate ΔG.
15. For the phosphorylation of glucose to glucose-6-phosphate, ΔG° = 14.0 kJ mol-1 at 37 °C. What is the equilibrium
constant for the reaction? In a cell the concentrations are [glucose] = 4.5 x 10-2 M, [HPO4
2-] = 2.7 x 10 –3 M, [G-6-P] =
1.6 x 10 –4 M. Is the reaction at equilibrium? Comment on how it be made to go forward.

A

q

61
Q

Rozwiąż poniższe zadania:
1. Calculate the energy transfer required to prepare the water required for a cup of tea. Is this heat or work?
2. Calculate the power output (in Watts) of an adult human. Assume an adult requires 2500 kcal/day.
3. Assuming no losses, how hot would 10 litres of water get using 2500 kcal/day.
4. Could you heat water to this temperature by sitting in the bath (assuming the bathtub were perfectly insulated).
5. How fast are the electrons moving if we apply a potential of 10 kV?
6. Given molecules with two energy levels separated by an energy difference of 5 kJ mol-1 , what percentage of
molecules are in the upper state at –200 °C and + 200 °C?
7. What would you predict to be the temperature difference between the top and the bottom of a waterfall 200 m high?
8. Imagine shaking a thermos flask full of cream full of cream? What happens? Is there a change in internal energy?
What was the mechanism of any change in the internal energy?
9. A piece of sodium is dropped into water. What happens? Can you express this in terms of q, w, U and H? (Don’t worry
about the precise numbers - think signs)
10. What is the enthalpy of formation of methane, CH4?
ΔHcomb
Θ(H2) = –285.6 kJ mol–1;
ΔHcomb
Θ(Graphite) = –393.1 kJ mol–1
ΔHcomb
Θ(Methane) = –889.4 kJ mol–1
11. Estimate the the standard enthalpy change for the reaction H2O2 (l) → 2H2O (l) + O2(g). ΔHvap (H2O2) = 51.6 kJ mol-1;
ΔHvap (H2O) = 44 kJ mol-1.
12. Lysozyme denatures at 75.5 °C and the enthalpy of unfolding ΔHunf = 509 kJ mol-1. What is the entropy change, ΔS of
the transition?
13. What is the maximum efficiency of a power station operating at 200, 400 and 600 °C.
14. Adenosine triphosphate (ATP) can be hydrolysed to release its phosphate group. At the “physiological”, temperature
36 °C (pH7) it has been estimated that ΔH = -20.08 kJmol-1 and ΔS = + 35.21 JK-1mol-1., Estimate ΔG.
15. For the phosphorylation of glucose to glucose-6-phosphate, ΔG° = 14.0 kJ mol-1 at 37 °C. What is the equilibrium
constant for the reaction? In a cell the concentrations are [glucose] = 4.5 x 10-2 M, [HPO4
2-] = 2.7 x 10 –3 M, [G-6-P] =
1.6 x 10 –4 M. Is the reaction at equilibrium? Comment on how it be made to go forward.

A

q

62
Q

• The system is the immediate area of interest
• The surroundings interact with the system but do not
form a part of it
• The universe is the sum of system and surroundings.
• Systems can be open, closed, isolated or adiabatic.

• Intensive/Extensive properties do not/do depend on
sample size.
• If pressure is kept constant then ΔH = ΔU + pΔV = qp
Enthalpy is a state function (Hess’s Law)

• The Second Law: Entropy increases
• Entropy change is the ratio of heat transferred to
temperature q/T
• Entropy is a measure of how dispersed is the energy - S =
klnW
• Local entropy increases with temperature
• Typically entropy is largest for gases, than for liquids or for
solids. Value depends on degrees of freedom.
• Entropy is a measure of the “quality” of energy.
• Under conditions of constant pressure G = H - TS
G is energy available for useful work
• For spontaneous processes ΔG

A

s

63
Q

Przypomnienie:

A

• The Zeroth Law specifies that energy flows to equalize
differences in temperature
• Temperature is the quantity that determines the
distribution of thermal energy in a system. Higher
temperatures imply faster molecules or more populated
higher energy levels.

64
Q

Przypomnienie:

A

• The First Law states that energy is conserved. Energy is
a zero sum game.
• Internal energy, U, cannot be measured. Only changes
can be measured: ΔU = q + w
• q and w are mechanisms of energy transfer
• Energy changes can be measured by calorimetry i.e. by
conversion into temperature rise or phase change.

65
Q

Przypomnienie:

A

• The system is the immediate area of interest
• The surroundings interact with the system but do not
form a part of it
• The universe is the sum of system and surroundings.
• Systems can be open, closed, isolated or adiabatic.

66
Q

Przypomnienie:

A

• The Maxwell-Boltzmann distribution describes the
speeds of molecules or the occupation of energy levels.
• N2/N1 = exp(–ΔE/RT)

67
Q

Przypomnienie:

A

• Intensive/Extensive properties do not/do depend on
sample size.
• If pressure is kept constant then ΔH = ΔU + pΔV = qp
Enthalpy is a state function (Hess’s Law)

68
Q

Przypomnienie:

A

• The Second Law: Entropy increases
• Entropy change is the ratio of heat transferred to
temperature q/T
• Entropy is a measure of how dispersed is the energy -
S =klnW
• Local entropy increases with temperature
• Typically entropy is largest for gases, than for liquids or for
solids. Value depends on degrees of freedom.
• Entropy is a measure of the “quality” of energy.

69
Q

Przypomnienie:

A

• Under conditions of constant pressure G = H - TS
G is energy available for useful work
• For spontaneous processes ΔG

70
Q

Przypomnienie:

A

• Chemical potential, μ, measures the driving force for a
process.
• Diffusion, osmosis, are driven by chemical potential.
• Mixing and unmixing are entropy-driven processes.
• Protein folding and membrane formation are primarily
driven by entropy – by release of water
• Life is a manifestation of energy flows

CHEM1602 (7 decks)

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