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BIOL1021 > Thermodynamics > Flashcards

Thermodynamics Flashcards

1
Q

What are the forms of energy?

A
  1. Kinetic energy
  2. Potential energy
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2
Q

What is kinetic energy?

A

The energy that an object or a system possesses due to its motion

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3
Q

Whats kinetic energy and its formula?

What is it related to?

A

For a particle with mass, m, and a velocity, v, we can evaluate the kinetic energy as:

Ekin= 1/2 MV2

Kinetic energy is related to temperature

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4
Q

Whats potential energy?

A

The stored energy in an object or system due to its position or configuration

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5
Q

Whats chemical bond energy?

A

Chemical bond energy is the energy stored in chemical bonds

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6
Q

Tell me if the following release or require energy?

  • bond formation
  • bond cleavage
A

Bond formation releases energy

Bond cleavage requires energy

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7
Q

What are the 3 forms of system?

A
  1. open system
  2. closed system
  3. isolated system
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8
Q

Whats an open system?

A

Both matter and energy can be transferred between the system and the surroundings

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9
Q

Whats a closed system ?

A

Only energy can be transferred between the system and the surroundings

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10
Q

Whats an isolated system ?

A

Neither matter nor energy can be transferred between the system and the surroundings

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11
Q

Whats the simplest system?

A

Isolated system is the simplest system

Energy and contents in isolated system is constant

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12
Q

Whats the 1st law of thermodynamics?

A

The sum of energies of a system and its surroundings remain constant

  • energy cannot be created or destroyed
  • energy can only be transferred between different forms
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13
Q

Give a real world example of the 1st law of thermodynamics?

A

Real world example of this:

  • Dam (or waterfall). Raises the water level of the river to create falling water. The reservoir that is formed is, in effect, stored energy.
  • Turbine. The force of falling water pushing against the turbine’s blades causes the turbine to spin. The turbine converts the kinetic energy of falling water into mechanical energy.
  • Generator. Connected to the turbine by shafts. When the turbine spins the generator will also spin, converting the mechanical energy from the turbine into electrical energy

stored (potential) energy → kinetic energy → mechanical energy → electrical energy

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14
Q

The energy derived from pressure and volume change is given by what?

A

E= pV (a type of work)

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15
Q

Define enthalpy, H?

A

H= U + pV

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16
Q

Whats the formula for the change of enthalpy of a system?

A

∆H= ∆U + ∆(pV)

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17
Q

since in biology most measurements are made at constant pressure, p=pconst we can assume there is no change in p. Therefore…?

A

∆ (pV) = p∆V (for constant p)

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18
Q

Whats the formula for internal energy?

How can work be described? With this define ∆H?

A

∆U = w + q

w= -∆(pV)

w= p∆V

therefore;

∆H= w + q + p∆V

∆H= -p∆V + q + p∆V

∆H= q

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19
Q

Whats an endothermic reaction?

A
  • Heat flowing into a system from its surroundings is defined as positive, (+q)
  • A process that absorbs heat from the surroundings is called endothermic.
  • So, the system gains heat, the surroundings cool down.
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20
Q

Whats an exothermic reaction?

A
  • When the heat flows out of the system into the surroundings, the heat flow is given a negative value (-q)
  • A process that gives heat to the surroundings is called an exothermic process.
  • The system loses heat, whereas the surroundings heat up.
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21
Q

Give an example of a real world example of an endothermic and exothermic reaction?

A

Ice melting= endothermic process

Explosion= exothermic process

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22
Q

Whats the 2nd law of thermodynamics?

A

In an isolated system the entropy can only ever increase.

If i have a closed system, I need to evaluate the entropy of the system and the surroundings

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23
Q

What are the quantities describing a system and examples?

A

Macrostates: Temperature, Pressure, Volume

Microstates: Kinetic energy, Force, Velocity

e.g. assign mass, velocity, position for any particle in a system at any time

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24
Q

What can macrostates be described as?

A

A collection of microstates

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25
Q

Whats the definition of equilibrium?

A

Macrostates do no change over time (necessary condition for macrostate to be well-defined)

In contrast microstates can be specified at any time

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26
Q

Whats entropy, S?

A

It is defined by the number of microstates, Ω, of a system

27
Q

Whats the number of microstates at a given total energy described as?

28
Q

The Boltzmann constant is: kB = 1.38064852 × 10-23 m2 kg s-2 K-1

Whats the formula relating entropy and the boltzmann constant?

A

S= KB ln(Ω)

29
Q

What does the microscopic state refer to?

A

The exact states of all the molecules making up the system

30
Q

Whats the formula for Clausius inequality?

A

∆S ≥ ∆q/T

∆q= heat exchange

T= temperature of the heat exchange

31
Q

Describe ∆q in either reversible or irreversible processes?

A

∆q in reversible process: ∆S= ∆q/ T (this is the definition of entropy)

∆q is irreversible process: ∆S > ∆q/T

32
Q

Whats the formula for gibbs free energy?

A

∆G= ∆H - T∆S

33
Q

For a reaction to be spontaneous, what must ∆G be?

34
Q

Whats the formula for the relation between ∆G and the equilibrium constant, Kc?

35
Q

Example reactions

36
Q

Whats the Chemical potential,µ, of the system?

A

The free energy per mole of that compound under a given set of conditions

37
Q

What is µ also referred to as?

A

The partial molar Gibbs free energy

38
Q

Chemical potential is an intensive state function that is independent of the system size.

What is meant by a state function?

A

a quantity in thermodynamics, such as entropy or enthalpy, that has a unique value for each given state of a system

39
Q

The useful measure of the average energy of a molcule depends only on what?

A

environment, not system size

40
Q

Whats the chemical potetial definition for a one component system?

A

µ= G/n

OR

G= µn

(n is the number of moles)

41
Q

Whats the chemical potetial definition for a multicomponent system?

A

G= ∑xµxnx

It is the sum of the chemical potentials of all the species present

42
Q

The change in free energy for removal of reactants is described as what?

A

Here ∆n is negative (nunber of moles of reactant is decreasing)

43
Q

The change in free energy for addition of products is described as what?

A

Here ∆n is positive (number of moles of product is increasing)

44
Q

Whats the equation for the sum of two expressions to get the overall change in free energy?

45
Q

Complete this calculation…

Given the chemical potentials of ATP, AMP, Pi and H2O, what is the free energy change for the hydrolysis of one mole of ATP to AMP?

46
Q

Here is a simple reaction; A⇔B

Use this equation to write the free energy equation?

How will the reaction be spontaneous?

A

A⇔B

This can be written as; ∆G = µBn - µAn

If µB is less than µA, then ∆G will be negative and the reaction will be spontaneous: as the µB and µA are positive

Here the criterion for spontaneous change is lowering of the chemical potential.

Equilibrium occurs when the chemical potentials are equal (µB=µA​)

47
Q

For this complex reaction; aA + bB ⇔ cC + dD

Whats the equation for the free energy?

What are the conditions for a spontaneous change?

A

Free change energy is given by: ∆G= µx∆nx= cµc + dµD - aµA - bµB

For a spontaneous change cμc + dμD must be less than aμA + bμB

48
Q

What is a spontaneous change?

A

The weighted sum of the chemical potentials can be lowered

49
Q

Whats an equilibrium?

A

The weighted sums of chemical potentials for reactants and products are equal

50
Q

Whats the equation that relates free energy of an ideal gas to its pressure?

A

G=G° + nRTlog(P/P°)

51
Q

Whats the equation for a pure compound that relates the free energy of an ideal gas to its pressure?

A

Recall that μ for a pure compound is equal to G/n

μ =μ°+ RTlog(P/P°) ⇒ divided the above equation by n to get this

52
Q

The equation for µ can be extended to one component of a mixture of ideal gases, what is this equation?

A

μ =μx°+ RTlog(Px/P°x)

Here Px is the partial pressure of x (the pressure exerted by x). The total pressure would be the sum of the partial pressures of all different gases in the mixture

53
Q

is free energy dependent on concentration?

54
Q

Consider the multi-component reaction; aA + bB ⇔ cC + dD

Whats the equation that describes the relationship between the free energy and the change in concentration of the components?

55
Q

For convenience, the term [Product]/[reactants] is often referred to as the mass action ratio. What symbol is this given ?

A

it is given the symbol, Γ

56
Q

Whats the equation for free energy, involving the mass action ratio, when the reaction is not in equilibrium?

A

ΔG=ΔG° + RTlogeΓ

57
Q

At equilibrium, ∆G=0, the mass action ratio at equilibrium is called the equilibrium constant, K. Whats the equation for free energy now?

A

ΔG°= -RTlogeK

58
Q

What are the units for K and Γ?

A

They don’t have units

59
Q

Are Loge and ln equal?

60
Q

Recall that the equilibrium constant of a reaction also varies with temperature (the position of the equilibrium is affected by temperature).

We have also seen the following equations, combine then to work out LogeK?

61
Q

Draw the graphs for the exo- and endothermic reactions with LogeK on the y-axis and 1/T (1/K) on the x-axis.

Whats the gradient?

Whats the intercept?

A
  • Should produce a straight line
  • Negative slope for -∆H˚/R, then it is an endothermic reaction
  • Positive slope for -∆H˚/R, then it is an exothermic reaction
  • Never really hit zero and otherwise it’s a very high temperature being used
  • Intercept corresponds to infinite temperature
62
Q

Whats the Van’t Hoff isochore?

63
Q

How can the total free energy, ∆G, of a system be obtained?

A

By adding together the chemical potentials multiplied by the amount of all the components of the system

64
Q

The variation of ∆G with concentration for a reaction is related to what?

A

The mass action ratio

BIOL1021 (12 decks)

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