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CHEM1020 - Fundamental Chemistry Theory and Practical > Physical Chemistry: Reactivity > Flashcards

Physical Chemistry: Reactivity Flashcards

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1
Q

What is thermodynamics?

A

The study of the way different types of energy interconvert.

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2
Q

What is the system?

A

The part of the world being studied.

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3
Q

What are the surroundings?

A

The rest of the world outside of the system.

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4
Q

What can be measured about a system?

A

The energy change of a system.

The energy of a system cannot be measured.

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5
Q

What is an open system?

A

A system where both matter and energy can be exchanged with the surroundings.

For example, a reaction taking place in a beaker.

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6
Q

What is a closed system?

A

A system that contains a fixed amount of matter but energy can be exchanged.

For example, a sealed reaction vessel.

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7
Q

What is an isolated system?

A

A system where there can be no exchange of energy or matter with the surroundings.

For example, a sealed, insulated vacuum flask.

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8
Q

What is energy?

A

The capacity to do work.

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9
Q

How is work done?

A

When moving against a force.

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10
Q

What is the equation for work done?

A

w = Fs

w = Work Done (J)
F = Force (N)
s = Distance (m)

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11
Q

What is the internal energy?

A

The total capacity for a system to do work.

It is denoted by the symbol, U.

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12
Q

What is the intermolecular potential energy in an ideal gas?

A

Zero.

This is because there are no forces between the molecules.

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13
Q

What does the internal energy of an ideal gas depend on?

A

Temperature, as the internal energy is purely kinetic.

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14
Q

What is the internal energy of an ideal gas independent of?

A

The volume.

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15
Q

What is the first law of thermodynamics?

A

Energy can neither be created nor destroyed, it can only be transformed from one form into another.

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16
Q

If work is done by a system, what happens to its internal energy?

A

It decreases.

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17
Q

If work is done on a system, what happens to its internal energy?

A

It increases.

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18
Q

What is heat?

A

Energy that flows from high-temperature objects to low-temperature objects.

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19
Q

What is thermal equilibrium?

A

Where there is no heat flow between two objects as they are the same temperature.

This is sometimes called the 0th law of thermodynamics.

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20
Q

What is the molar heat capacity equation?

A

q = nCΔT

q = amount of heat supplied (J)
n = amount of substance (mol)
C = molar heat capacity (J mol⁻¹ K⁻¹)
ΔT = change in temperature (K)

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21
Q

How can the molar heat capacity be measured in gases?

A

It can be measured in two ways: at a constant pressure (Cₚ) or constant volume (Cᵥ).

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22
Q

What is the heat capacity of a substance related to?

A

The number of degrees of freedom possessed by its molecules.

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23
Q

What are the two types of work?

A

Expansion work.

Non expansion work.

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24
Q

What is expansion work?

A

Involves a change in the volume of the system.

For example, the work done by a reaction with gaseous products.

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25
Q

What is non-expansion work?

A

Does not involve a change in volume of the system.

For example, the electrical work done by a battery.

26
Q

What is the irreversible constant pressure expansion equation?

A

W = pₑₓΔV

W = work done (J)
pₑₓ = external pressure
ΔV = change in volume

27
Q

What corresponds to the area under a Boyle’s Law curve?

A

The work done for an ideal gas expanding reversibly at a constant temperature.

28
Q

What is a statement of the second law of thermodynamics?

A

A process must occur reversibly to do the maximum possible work.

29
Q

What is the equation of internal energy when work and heat are taken into account?

A

ΔU = q + w

ΔU = change in internal energy
q = heat (it is positive if heat is supplied to the system and negative if heat is released by the system)
w = work (positive if work is done on the system, negative if work is done by the system).

30
Q

In an ideal gas, if the temperature is kept constant, what happens the internal energy.

A

It remains constant too.

31
Q

What are the consequences of the first law of thermodynamics?

A

Energy is conserved - heat and work are equivalent forms of energy.

For a system at constant volume, there is no expansion work.

Internal energy is a state function.

32
Q

What are state functions?

A

Quantities such as pressure, volume, temperature which depend only on the state of the system.

If the system is changed from one state to another, the change in a state function is independent of how the change was brought about.

33
Q

What are path functions?

A

Quantities like work and heat which depend on the path between the states.

Path functions depend on how the change was brought about.

34
Q

What is an intensive property?

A

A property that does not depend on the quantity of the substance present.

35
Q

What is an extensive property?

A

A property that depends on the quantity of the substance present.

36
Q

What is enthalpy?

A

The heat change at a constant pressure.

37
Q

What is enthalpy defined as?

A

H = U + pV

38
Q

What is the change in enthalpy equal to?

A

ΔH = ΔU + pΔV
= q + w + pΔV
= q - pΔV + pΔV
= qₚ

39
Q

What is the heat transferred at a constant pressure (qₚ) equal to?

A

qₚ = nCₚΔT

40
Q

What is an exothermic process?

A

ΔH < 0, so heat is released from the system at constant pressure.

41
Q

What is an endothermic process?

A

ΔH > 0, so that heat is absorbed by the system at constant pressure.

42
Q

What is the standard molar enthalpy of melting?

A

The enthalpy change which occurs when 1 mol of a pure solid melts to form a liquid at its melting point and 1 bar pressure.

43
Q

What is the standard molar enthalpy of vapourisation?

A

The enthalpy change which occurs when 1 mol of a pure liquid boils to form a gas at its boiling point and 1 bar pressure.

44
Q

What is Hess’s Law?

A

The overall reaction enthalpy is the sum of the reaction enthalpies of the steps into which the reaction can be divided.

45
Q

What type of function is enthalpy?

A

A state function.

This allows Hess’s law to be true, as its value is independent of the path chosen.

46
Q

What is the standard enthalpy of formation?

A

The standard reaction enthalpy for the formation of a compound in its standard state from elements in their standard state.

47
Q

What is the standard enthalpy of for an element in its standard state?

A

Zero.

48
Q

How is the enthalpy change for a reaction calculated?

A

The sum of the enthalpy of the products - the sum of the enthalpy of the reactants.

49
Q

What is electrochemistry?

A

The study of chemical reactions that take place at the surface of an electrode.

50
Q

What is an electrode?

A

An electronic conductor which is immersed in an electrolyte.

51
Q

What is an electrolyte?

A

An ionic conductor that is usually an ionic solution.

52
Q

What reactions occur at electrodes?

A

Redox reactions.

53
Q

What is an electrochemical cell?

A

Two electrodes in contact with an electrolyte.

54
Q

What is a galvanic cell?

A

A cell that produces electricity when a spontaneous reaction takes place within the cell.

55
Q

What reaction occurs at the anode?

A

Oxidation.

56
Q

What reaction occurs at the cathode?

A

Reduction.

57
Q

What is an electrolytic cell?

A

A cell where a non-spontaneous reaction is driven by an external current.

58
Q

What is a salt bridge?

A

A tube which contains a concentrated salt solution. It allows ions to flow between the electrolytes.

59
Q

How many degrees of freedom does a molecule have?

A

3 times the number of atoms.

60
Q

How many vibrational modes does a linear molecule have?

A

3N - 5.

(Where N is the number of atoms)

61
Q

How many vibrational modes does a non-linear molecule have?

A

3N - 6.

(Where N is the number of atoms)

CHEM1020 - Fundamental Chemistry Theory and Practical (7 decks)

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