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A-Level Chemistry > Topic 13 Energetics 2 > Flashcards

Topic 13 Energetics 2 Flashcards

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1
Q

What is a lattice?

A

A regular three-dimensional arrangement of atoms or ions in a crystal.

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2
Q

What is ionic bonding?

A

The strong electrostatic forces between oppositely charged ions in a lattice.

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3
Q

What is the standard enthalpy change of formation?

A

The enthalpy change when ONE MOLE of a SUBSTANCE is formed form its constituent ELEMENTS under STANDARD CONDITIONS.

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4
Q

What is the standard enthalpy change of combustion?

A

The enthalpy change when ONE MOLE of a SUBSTANCE undergoes COMPLETE COMBUSTION in OXYGEN under STANDARD CONDITIONS.

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5
Q

What is the standard enthalpy change of neutralisation?

A

Enthalpy change when ONE MOLE of WATER is formed in a reaction between an ACID and ALKALI under STANDARD CONDITIONS.

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6
Q

What is ionisation enthalpy?

A

First Ionisation Enthalpy:
The enthalpy when each atom in ONE MOLE of GASEOUS atoms lose ONE ELECTRON to form ONE MOLE of GASEOUS 1+ IONS.

Second Ionisation Enthalpy:
The enthalpy when each ion in ONE MOLE of GASEOUS 1+ IONS lose ONE ELECTRON to form ONE MOLE of GASEOUS 2+ IONS.

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7
Q

What is electron affinity?

A

First Electron Affinity:
The enthalpy when each atom in ONE MOLE of GASEOUS atoms gain ONE ELECTRON to form ONE MOLE of GASEOUS 1- IONS.

Second Electron Affinity:
The enthalpy when each ion in ONE MOLE of GASEOUS 1- IONS gain ONE ELECTRON to form ONE MOLE of GASEOUS 2- IONS.

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8
Q

What is the standard enthalpy change of atomisation?

A

The enthalpy change when ONE MOLE of GASEOUS ATOMS is produced from an element in its STANDARD STATE.

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9
Q

What is hydration enthalpy?

A

The enthalpy change when ONE MOLE of GASEOUS IONS become hydrated (dissolved in water).

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10
Q

What is the standard enthalpy change of solution?

A

The enthalpy change when ONE MOLE of an IONIC SOLID dissolves in water (volume of water must be large enough to ensure ions are well separated and therefore do not interact with each other).

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11
Q

What is bond dissociation enthalpy?

A

The enthalpy change when ONE MOLE of COVALENT BONDS are broken in the GASEOUS STATE.

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12
Q

What is the standard lattice enthalpy change of formation?

A

The enthalpy change when ONE MOLE of a SOLID IONIC COMPOUND is formed from its constituent ions in the GAS PHASE.

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13
Q

What is the standard lattice enthalpy change of dissociation?

A

The enthalpy change when ONE MOLE of an SOLID IONIC COMPOUND is broken up into its constituent ions in the GAS PHASE.

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14
Q

What is the standard enthalpy change of vapourisation?

A

The enthalpy change when ONE MOLE of a LIQUID is turned into a GAS.

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15
Q

What is the standard enthalpy change of fusion?

A

The enthalpy change when ONE MOLE of a SOLID is turned into a LIQUID.

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16
Q

What is the song to remember Born-Haber cycles?

A

Atomisation of the metal, Atomisation of the non-metal, Ionisation of the metal, Electron affinity, Lattice Enthalpy. (Generally used to find the standard enthalpy change of formation).

17
Q

What is polarisation?

A

The distortion of the energy cloud in a molecule or ion by a nearby positive charge.

18
Q

What is polarising power?

A

The ability of a positive ion (cation) to distort the electron cloud of a neighbouring negative ion (anion).

19
Q

What is polarisability?

A

An indication of the extent to which the electron cloud in a molecule or an ion can be distorted by a nearby electric charge.

20
Q

What factors affect lattice enthalpy?

A

Ionic Radius - Larger ions result in a weaker lattice and therefore a weaker lattice enthalpy.

Ionic Charge - Higher ion charge results in a strong attraction between ions and therefore a stronger lattice enthalpy.

21
Q

What are the entropy equations?

A

ΔS (system) = Products - Reactants

ΔS (surroundings) = - ΔH / T

ΔS (total) = ΔS (systems) + ΔS (surroundings)
or
ΔS = R ln K

ΔG = ΔH - TΔS(system)
or
ΔG = -RT ln K

22
Q

What does the term feasible mean?

A

This describes if a reaction can naturally occur (ignoring the activation energy that may be required).

23
Q

How do you know if a reaction is feasible?

A

If the ΔS (total) is positive the reaction is feasible.

If the ΔG is negative the reaction is feasible.

24
Q

What is the standard molar entropy?

A

The entropy per mole for a substance under standard conditions. (S)

25
Q

When is the only time that the entropy is 0 JK⁻¹mol⁻¹ ?

A

The entropy is 0 JK⁻¹mol⁻¹ in a perfectly ordered crystal at 0K.

26
Q

What predictions for ΔS (system) can be made by looking at the reaction equation?

A
  • If a gas is formed from non-gaseous reactants, entropy will increase.
  • If a gas reacts and a gas is not produced, entropy will decrease.
27
Q

What predictions for ΔS (surroundings) can be made by looking at the reaction equation?

A
  • For exothermic reactions, entropy always increases.
  • For endothermic reactions, entropy always decreases.
  • The magnitude of the entropy depends on the temperature of the surroundings and enthalpy change.
28
Q

How can the temperature that a feasible reaction can occur at be calculated?

A

Rearranging the ΔG equation (when ΔG = 0 ) gives:
T = ΔH / ΔS (system)
Then simply insert the values to work out the temperature.

29
Q

What is free energy change?

A

The thermochemical quantity used by chemists to decide whether a reaction tends to occur and how far it will go. ΔG is the test for the feasibility of a reaction.

30
Q

What does thermodynamically stable mean?

A

A chemical or mixture of chemicals is thermodynamically stable if there is no tendency for the reaction. Therefore, there will be a positive ΔG indicating that it doesn’t occur.

31
Q

What does kinetically inert mean?

A

A chemical or mixture of chemicals is kinetically inert when a reaction does not occur even though it is feasible.

A-Level Chemistry (20 decks)

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