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CHEM1603 CH > Section C > Flashcards

Section C Flashcards

1
Q

Which biological processes are driven by light?

A

Synthesis of cellular macromolecules/membranes/phospholipids/metabolites, cellular movements, active transport, electrical potential generation, heat

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2
Q

Is heat a form of energy?

A

No, it’s fucking not

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3
Q

What is specific heat capacity?

A

Energy required to raise 1g of water by 1 degree

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4
Q

How many Joules is in 1 calorie?

A

4.2J

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5
Q

What is specific latent heat?

A

Energy change in Joules required to convert 1kg of mass from solid to liquid phase

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6
Q

What is a calorimeter?

A

Insulated device to measure temperature change in specific reaction

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7
Q

What is Kleiber’s law?

A

P proportional to M^3/4 (P = metabolic rate, M=mass)

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8
Q

What is the equation for metabolic rate?

A

P=dE/dT (rate of energy conversion)

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9
Q

Define an open system

A

System may exchange energy and matter with surroundings

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10
Q

Define a closed system

A

System may exchange energy with surroundings but not matter

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11
Q

Define an isolated system

A

No exchange can occur in system

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12
Q

Define the surroundings

A

everything around the system that has physical contact with it - may or may not exchange heat or matter

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13
Q

What does a Maxwell-Boltzmann distribution curve show?

A

how energy is distributed, distribution is typically asymmetrical (weighted toward lower speeds)

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14
Q

What happens to Maxwell-Boltzmann curve as temperature increases?

A

Curve flattens and moves to right (more particles at higher speeds)

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15
Q

What is the equation using population states (very important!)?

A

Population state in En/Population state in E0 = e^-[(En-E0)/kT] (k=boltzmann constant)

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16
Q

What is the value and units of Boltzmann constant?

A

1.38 x 10^-23 J/K

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17
Q

What is temperature a measure of?

A

Average energy of a system

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18
Q

What increases with increasing temperature?

A

occupancy of higher energy levels increases with temperature

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19
Q

What increases with decreasing temperature?

A

proportion of lower energy states increases as temperature decreases

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20
Q

What is the Zeroth law of thermodynamics?

A

Energy flows between objects to equalise their temperatures, temperature shows which was energy will flow (like pressure)

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21
Q

What is an intensive property?

A

Intensive property is not additive & does not depend on amount of material, e.g. temperature

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22
Q

What is the first law of thermodynamics?

A

Internal energy U is the sum total of all possible energies in the system

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23
Q

Can the absolute value of U (internal energy) be determined?

A

No it fucking can’t

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24
Q

What is an extensive property?

A

Extensive property is additive - depends on the amount of material present e.g. energy

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25
Q

What is the equation for change in internal energy?

A

Delta U = q + w (q=heat transferred to system, w=work done on system)

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26
Q

What is a state function?

A

value is path independent (how you arrive) e.g. U, altitude

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27
Q

What normally represents a state function?

A

A capital letter

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28
Q

What is another name for ‘path independant’ on state functions?

A

Zero-Sum game

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29
Q

What is the definition of heat?

A

Transfer of energy due to a difference in temperature between system and surroundings -> change in random motion of atoms

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30
Q

What is the definition of work?

A

Transfer of energy to or from the system which results in coordinated/coherent motion of molecules in a system

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31
Q

What is the major difference between heat and work?

A

Heat involves a change in random motion of particles, work results in coordinated motion of particles

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32
Q

Is heat a form of energy?

A

NO it’s fucking not, it’s a transfer of energy

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33
Q

What is the change in any property taken in relation to?

A

the system, change in any property is with respect to the system

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34
Q

Is a reaction endothermic or exothermic if q > 0?

A

Endothermic, energy moving from surrounding to system

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35
Q

Is a reaction endothermic or exothermic if q

A

Exothermic, energy moving from system to surroundings

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36
Q

What is the case if w > 0?

A

Surroundings do work on system -> gains energy

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37
Q

What is the case if w

A

System does work on surroundings -> loses energy

38
Q

What type of function is enthalpy?

A

State

39
Q

What are 3 equations for work done (w)?

A

Work = -Fx = -pAx = -p.delta v

40
Q

What is the equation for pressure?

A

P = F/A (F=force, A=area)

41
Q

What is equal to change in enthalpy provided pressure and volume are kept constant?

A

q (heat transferred to system) = change in enthalpy -> delta H

42
Q

Is a process endothermic/exothermic if delta H > 0?

A

endothermic, positive delta H is an endothermic reaction

43
Q

Is it possible to calculate the absolute enthalpy of a substance?

A

No, only possible to calculate change in enthalpy (H) using thermochemical cycles

44
Q

What conditions is H normally referenced to?

A

1mole (pure), 298.15K, 1bar (0.986932Atm)

45
Q

What is the enthalpy of dissociation for H2?

A

436kJ/mol - endothermic process

46
Q

What is the mean bond enthalpy?

A

average amount of energy needed to break a specific bond, measured over a wide range of molecules

47
Q

What is the symbol for mean bond enthalpy?

A

Delta HB

48
Q

What is Kirchoff’s law?

A

Describes variation of a reaction’s enthalpy with varying temperature (enthalpy increases with temperature)

49
Q

On a plot of H vs T, how would you find heat capacity?

A

Heat capacity is the gradient of this plot, Cp = dH/dT

50
Q

What is assumed about Cp (heat capacity)?

A

It remains constant over small temperature ranges

51
Q

What is the equation using Cp to find enthalpy change?

A

Delta H2 = Delta H1 + Cp(T2-T1) (Delta H2 = enthalpy change at Temp. 2)

52
Q

How do we calculate the enthalpy of protein folding?

A

Use isothermal calorimetry

53
Q

How does isothermal calorimetry work?

A

2 chambers linked by feedback mechanism to keep temperature identical, acid/salt injected to unfold protein/ligand added to bind protein, measure temperature change/energy = enthalpy

54
Q

What can the first law of thermodynamics not predict?

A

Direction of enthalpy change, only shows that work can be converted directly into heat

55
Q

What function can show direction of enthalpy change?

A

Entropy

56
Q

What is the equation for connecting entropy, heat and temperature?

A

Change in entropy = q/T (q=work, t=temp)

57
Q

What type of reaction minimise entropy change?

A

Reversible reactions

58
Q

What does adiabatic mean?

A

Completely isolated from world, ‘Isolated System’

59
Q

What does this equation show? Delta S total = Delta S universe > 0

A

Equation shows that the entropy of the universe will always increase, if entropy change is positive then entropy increases = more random

60
Q

How do we prove the equation showing entropy always increases?

A

Entropy change is always negative for hotter substances, whereas it is positive for colder substances, so entropy change hot

61
Q

What is the second law of thermodynamics?

A

In any spontaneous process entropy increases, entropy of universe is increasing,

62
Q

How do we work out efficiency from entropy?

A

using the fact that entropy change of hot + cold = 0, can then convert to q/T -> waste q/cold temp - transferred q/hot temp -> rearrange to get max power = transferred q x (1-(hot temp/cold temp))

63
Q

What is the equation to work out max work (find efficiency)?

A

W max = transferred q x (1 - (hot temp/cold temp))

64
Q

What is the equation for entropy of a phase change at constant T?

A

Change in entropy = change in enthalpy/temperature

65
Q

What is the third law of thermodynamics?

A

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

66
Q

Which has the highest molar entropy: gas, liquid or solid?

A

Gas, greatest degrees of freedom

67
Q

What does entropy measure?

A

The quality of energy -> how narrowly it is distributed

68
Q

What is the equation for configurational entropy?

A

S proportional to lnW

69
Q

What are the two most important equations for boltzmann/entropy?

A

S = k.lnW and S >/= q/T

70
Q

What is the mole fraction and what is it’s symbol?

A

xA = moles of A / moles of everything in sample (no units) -> e.g. nA/(nA + nB)

71
Q

What is molaLity?

A

Moles of solute / Mass of solvent -> moles/kg

72
Q

Mole fraction is proportional to molality

A

HELL YEH FUCKIN RIGHT

73
Q

What is the equation for entropy of mixing/expansion?

A

Delta S = n.R.ln(V2/V1) if V2 = volume of area which gas has expanded into

74
Q

Is the change in enthalpy of mixing always positive or negative?

A

Always positive, so mixing is a spontaneous process

75
Q

What does isothermal mean?

A

constant temperature

76
Q

Why are biological systems isothermal?

A

They do not rely on temperature difference to do work, typically cell transfers energy out into surroundings but this means pV work cannot be done (pressure, volume)

77
Q

What is the equation for Gibbs free energy?

A

Delta G = Delta H - T.Delta S

78
Q

What is the definition of gibbs free energy?

A

Energy gathered from a change in the system which is available to do non-pV work

79
Q

What type of reaction is occurring if Delta G is greater than 0?

A

Endergonic reaction

80
Q

What biological reaction is spontaneous at all temperatures?

A

Conversion of glucose and oxygen into CO2 and H2O, forward reaction has a negative enthalpy change and positive entropy change (and ATP-> ADP + Pi)

81
Q

What does the symbol mu stand for?

A

Chemical potential

82
Q

What is chemical potential?

A

A measure of how Gibbs free energy changes per molecule of substance, how seep gradient is

83
Q

What form of substance is mu at its highest?

A

Highest mu in a pure liquid

84
Q

What is the equation for chemical potential (mu) of a gas?

A

mu = mu0 + RT.lnP (P=pressure)

85
Q

What changes in the equation for chemical potential in solids and liquids?

A

lnP changes to lnX, where X is the number of moles

86
Q

What is the equation for standard gibbs free energy?

A

Delta G0 = -RT.lnKeq (K=equilibrium constant)

87
Q

Which direction would diffusion occur if chemical potential was higher in A than B?

A

particles would diffuse from A into B

88
Q

What is the equation for osmotic pressure (pi)?

A

pi = cRT (c=solute concentration)

89
Q

What is a very important example of an entropic effect?

A

Formation of lipid bilayers, clustering of non-polar molecules to form membranes

90
Q

If a non-polar molecule is surrounded by water, is it an endothermic or exothermic process?

A

Endothermic process, due to polar head group, so enthalpy change is positive, formation of bilayers is favourable due to an overall positive entropy change due to the release of a lot of organised solvent

CHEM1603 CH (6 decks)

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