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AQA A Level Chemistry > Physical Chapter 6: Thermodynamics > Flashcards

Physical Chapter 6: Thermodynamics Flashcards

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1
Q

What is the symbol for enthalpy change?

A

ΔH

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2
Q

What is enthalpy change defined as?

A

The heat energy transferred in a reaction at a constant pressure

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3
Q

What is enthalpy change of formation?

A

The enthalpy change when 1 mole of a compound is formed from its elements in their standard states under standard conditions

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4
Q

What is enthalpy change of atomisation?

A

The enthalpy change when 1 mole of an element or compound in standard state is converted to gaseous atoms.

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5
Q

What is lattice dissociation enthalpy?

A

The enthalpy change when all the bonds of the same type in 1 mole of gaseous molecules are broken

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6
Q

What is first ionisation energy?

A

The enthalpy change when 1 mole of gaseous 1+ ions is formed from 1 mole of gaseous atoms

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7
Q

What is second ionisation energy?

A

The enthalpy change when 1 mole of gaseous 2+ ions is formed from 1 mole of gaseous 1+ ions.

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8
Q

What is first electron affinity?

A

The enthalpy change when 1 mole of gaseous 1- ions is formed from 1 mole of gaseous atoms

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9
Q

What is second electron affinity?

A

The enthalpy change when 1 mole of gaseous 2- ions is formed from 1 mole of gaseous 1- ions.

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10
Q

What is enthalpy change of hydration?

A

The enthalpy change when 1 mole of aqueous ions is formed from 1 mole of gaseous ions

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11
Q

What is enthalpy change of solution?

A

Enthalpy change when 1 mole of solute is dissolved in enough solvent that no further enthalpy change occurs on further dilution.

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12
Q

What is lattice enthalpy a measure of?

A

Bond Strength

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13
Q

How do we calculate lattice enthalpies?

A

Born-Haber Cycles

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14
Q

What do you have to do to values for enthalpy if you are forming 2 moles in a born-haber cycle?

A

Double the value

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15
Q

Why are theoretical lattice enthalpies often different from experimental values?

A

They asume a purely ionic model, where all ions are spherical. This doesn’t account for covalent character, where ions aren’t all spherical.

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16
Q

What happens when you dissolve a substance in water?

A

The bonds between the ions break - endothermic
Bonds between ions and water are made - exothermic
Enthalpy of solution is the overall effect of these 2 changes

17
Q

What enthalpies do you use to calculate enthalpy of solution?

A

Lattice dissociation and enthalpy of hydration

18
Q

What is Entropy?

A

A measure of how disordered something is.
More directly, a measure of how many possible ways the particles can be arranged.

19
Q

Which state has highest entropy?

A

Gas

20
Q

What is the effect of an increased number of particles on entropy?

A

Entropy increases

21
Q

What is the effect of higher entropy in stability?

A

More stable

22
Q

How do you calculate entropy change for a reaction?

A

Entropy of products - entropy of reactants

23
Q

How do you measure the feasability of a reaction?

A

Gibbs Free Energy must be negative or 0.

24
Q

What is Gibbs Free energy?

A

ΔG = ΔH -TΔS
(temperature in kelvin)

25
Q

How do you find the temperature when a reaction is just feasible?

A

T = ΔH/ΔS
(rearrangement of ΔG formula)

AQA A Level Chemistry (25 decks)

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