Physical Flashcards

1
Q

What is the zeroth law of thermodynamics?

A

If system A is in thermal equilibrium with B, and B is in thermal equilibrium with C, then C is also in equilibrium with A

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2
Q

What is the first law of thermodynamics?

A

Energy cannot be created or destroyed but it can be converted into another form

ΔU = q + w

ΔU = internal energy
q = heat
w = work
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3
Q

When work is done on a system, is w positive or negative?

A

Positive

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4
Q

When heat is gained by a system, is q positive or negative?

A

Positive

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5
Q

What are adiabatic systems?

A

Thermally insulated, isolated systems

Heat is not involved

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6
Q

What is an isothermal system?

A

Closed, not thermally isolated systems

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7
Q

What is an isovolumetric process?

A

Volume is constant, pressure and temperature can change

Heat is allowed to enter

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8
Q

What is an isobaric process?

A

Pressure is constant, volume and temperature can change

Heat is allowed to escape

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9
Q

What is an isothermal process?

A

Temperature is constant, pressure and volume can change

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10
Q

Adiabatic process

A

Pressure, volume and temperature can all change

Heat isn’t allowed to escape

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11
Q

What is the second law of thermodynamics?

A

ΔS univ > 0

Heat cannot spontaneously flow from a colder location to a hotter location

The total entropy of the universe always increases

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12
Q

What is the third law of thermodynamics?

A

S T=0 >= 0

As a system approaches absolute zero all thermal processes cease and entropy approaches a minimum

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13
Q

What is a perfect crystal?

A
  • when entropy = 0

- atoms or ions are arranged in a regular, uniform way

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14
Q

What is enthalpy and how can it be calculated from internal energy?

A

A measure of the total energy of a thermodynamic system

H = U + PV

U= internal energy

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15
Q

What are the two types of calorimeter?

A
  • constant volume

- constant pressure

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16
Q

Define specific heat capacity

A

The energy required to raise the temperature of 1g of substance by 1°C

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17
Q

State Hess’s Law

A

The enthalpy change for a reaction is independent of the route taken

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18
Q

Define electron affinity

A

The energy released when an electron is added to a gaseous atom

X(g) + e- -> X^- (g)

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19
Q

Define energy of atomisation

A

The energy needed to transform an element in its standard state into 1 mole of gaseous atoms

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20
Q

How does heat differ from temperature?

A

Heat is a measure of thermal energy flow

Temperature is the average thermal energy per atom

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21
Q

What is thermal energy?

A

The kinetic and potential energy associated with the movement of individual molecules and atoms

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22
Q

What is bond dissociation enthalpy and how does it differ from bind energy?

A

Bind dissociation enthalpy is the energy required to break 1 mole of specific binds at RTP

BDE is specific for a particular bind in a particular molecule

Bond energy is the average value to break a bond across various molecules

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23
Q

What is a spontaneous reaction?

A

A reaction that does occur under specific conditions

24
Q

What is a non-spontaneous reaction?

A

A reaction that does not occur under specific conditions

25
Q

Define standard entropy of reaction

A

The entropy change for a reaction carried out at 1 atm and 298K

Units of J K-1 mol-1

26
Q

Define Gibbs free energy

A

The energy available to do work at constant pressure

27
Q

Which gas law relates pressure and volume?

Give the equation for it

A

Boyle’s law

P1 V1 = P2 V2

28
Q

What does Gay-Lussac’s law involve? Give the equation

A

Temperature and pressure

P1 / T1 = P2 / T2

29
Q

What does Charles’s law relate? Give the equation

A

Temperature and volume

V1 / T1 = V2 / T2

30
Q

What relates volume and amount in gases? Give the equation

A

Avogadro’s law

V1 / n1 = V2 / n2

31
Q

Explain why the behaviour of a real gas might be different to predictions made using the ideal gas law

A

In an ideal gas, molecules do not attract or repeal one another

The volume is negligible compared with the volume of the container

Real gases act like ideal gases at 0°C and 100 kPa

32
Q

How would you calculate the density of a gas?

A

d = Mr P / RT

33
Q

What is the equation for calculating concentrations of gases?

A

C = P /RT

34
Q

What is Dalton’s law of partial pressures?

A

The total pressure of a mixture of gases is just the sum of the pressures that each gas would exert if it were present alone

35
Q

What does Boyle’s law state?

A

For a fixed mass of gas at constant temperature, the volume is inversely proportional to the pressure

36
Q

What does Charles’s law state?

A

For a fixed mass of gas at constant pressure, the volume is directly proportional to the temperature

37
Q

What does Gay-Lussac’s law state?

A

The pressure of a fixed amount of gas at a constant volume is proportional to temperature

38
Q

What does Avogadro’s law state?

A

The volume of a gas maintained at a constant pressure and temperature is proportional to the amount of gas

39
Q

What is the equation for calculating the partial pressure of a gas?

A

P = mole fraction x total pressure

40
Q

What is the equation for calculating mole fraction of a gas?

A

X = no. of moles of gas A / total number of moles of gas

41
Q

What is Le Cháteliers principal?

A

A system at equilibrium will oppose any change made to the system

42
Q

Equation that links equilibrium constant with Gibbs free energy

A

ΔG° = -RT ln(k)

43
Q

What is a bronsted acid?

A

Proton donor

44
Q

What is a bronsted base?

A

A proton acceptor

45
Q

What is the Henderson-Hasselbalch equation?

A

pH = pKa + log10([A-] / [HA])

46
Q

Explain what is meant by rate law and reaction order

A

Rate law expresses the relationship of the rate of a reaction to the rate constant and the concentrations of the reactants raised to some power

Reaction order is the sum of the individual orders in a reaction (the overall order)

47
Q

What is the intergrated rate equation for a zeroth order reaction?

A

[A] = [A]0 - nkt

48
Q

What is the equation for calculating the half-life of a zeroth order reaction?

A

t 1/2 = [A]0 / 2nk

49
Q

What is the integrated rate equation for a first order reaction?

A

[A] = [A]0 e^(-nkt)

50
Q

What is the equation for calculating the half-life of a first order reaction?

A

t 1/2 = ln(2) / nk

51
Q

What is the integrated rate equation for a second order reaction?

A

1/[A] = 1/[A]0 + nkt

52
Q

What is the equation for calculating the half-life of a second order reaction?

A

t 1/2 = 1/ nk [A]0

53
Q

What is half-life?

A

The time taken for the concentration of a reactant to drop to half of its initial value

54
Q

What is the equation relating Kp to Kc?

A

Kp = Kc (RT)^Δn

55
Q

What is the equation relating Kp to Kc?

A

Kp = Kc (RT)^Δn