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A Level Chemistry - physical chemistry > Therodynamics > Flashcards

Therodynamics Flashcards

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1
Q

What is atomisation enthaply and what type of reaction is it

A

The energy needed to produce one mole of free gaseous atoms of that atom in standard conditions and in its standard states and it’s endothermic

1/2Cl2(g)->Cl(g)

Na(s)->Na(g)

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2
Q

What is first ionisation energy and what type of reaction is it

A

The amount of energy needed to remove one electron from each mole of free gaseous atoms of that element to form positive ions it’s exothermic

Na(g)->NA+(g)+e-

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3
Q

What is first electron affinity and what type of reaction is it

A

The energy change when one electron is added to each of a mole of free gaseous atoms of that element for negative ions it’s exothermic

Cl(g)+e->Cl-(g)

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4
Q

What is second ionisation energy of an element

A

The energy needed to remove one electron from each mole of free positive ions of that element

Mg+(g)->Mg2+(g)e-

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5
Q

What is second electron affinity of an atom and what type of reaction is it

A

Its the energy change when one mole of electrons are added to a mole of gaseous atoms each with a single negative charge to form ions each with 2nd negative charges

It’s exothermic

O-(g)+e->O2-(g)

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6
Q

What is lattice enthalpy of formation

A

It’s a standard enthalpy change when one mole of solid ionic compound is formed from its gaseous ions

Na+(g)+Cl-(g)->Nacl(s)

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7
Q

What is enthaply of lattice dissociation and state the type of reaction it is

A

Is standard enthalpy change when one mole of solid ionic compound is dissociated into its gaseous ions

It’s endothermic (+)

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8
Q

What is enthaply of hydration

A

Its the standard enthalpy change when water molecules surround one mole of gaseous ions and become aqa ions

Na+(g) +aq->Na+(aq)

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9
Q

What is enthaply of solution

A

Standard enthalpy change when one mol of an ionic compound dissolves completely in water to form a solution in which don’t interact with one another

NACL-NACl(aq)

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10
Q

What reaction does this represent

Mg (s)->Mg (g)

A

Standard enthalpy of atomisation

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11
Q

What reaction does this represent

Mg(g)->Mg+ (g)+e-

A

First ionisation energy

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12
Q

What is mean bond enthaply

A

Energy change when I mole of gaseous molecules each break a covalent bond which is averaged over a range of compounds

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13
Q

Why are atomisation enthalpies endothermic

A

As bonds in the element need to be broken

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14
Q

Why are second ionisation energies more endothermic than first ionisation energies

A

As there is less repulsion between the remaining electrons in the ion so more energy is needed to remove the electrons

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15
Q

Why are second electron affinities endothermic

A

As the incoming electron is repelled by the negative charge on the ion so the value is positive

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16
Q

Why are lattice enthalpies of formation negative and why are lattice enthalpies of dissociation positive

A

Ionic bonds are being formed so it’s exothermic

Ionic bonds are being broken so it’s endothermic

17
Q

State the two ways to work amount enthaply change of solution

A

Hydration - lattice of formation

Hydration +lattice of dissociation

18
Q

What is entropy and how do you work it out

A

It’s the degree of disorder of a system higher degree the more stable it is

Products - reactant

19
Q

State what will become of the reaction when entropy is positive or negative

A

If entropy is positive the reaction is more likely

If it’s negative it’s less likely to occur

20
Q

State the free energy equation and what each symbol stands for

A

G=H-TS

G is change in free energy
H is change in enthaply
A change in entropy

21
Q

If G is positive what will happen

A

The reaction will not proceed

22
Q

If G is negative what will happen

A

The reaction will occur

23
Q

What will happen to the reaction of enthaply is negative and entropy is positive

A

The reaction is spontaneous at all temperature because theirs more disorder due to increasing entropy

24
Q

If enthaply is positive and entropy is negative what will happpen

A

The reaction won’t be spontaneous at any temperature

25
Q

What does it mean for the reaction if both entropy and enthalpy are positive

A

It means the reaction will be spontaneous above a certain temperature

26
Q

What does it mean if both enthaply and entropy are both negative

A

The reaction will only be spontaneous below a certain temperature

27
Q

How would you work out temperature in Gibbs free energy

A

T=H/S

28
Q

Which types of lattices have the higher lattice enthalpies

A

Smaller lattices this is because the cations and anions are closer together so they attract together more closely

29
Q

How is entropy worked out

A

Products - reactants

30
Q

In Gibbs free energy how is entropy worked out

A

Enthaply/Temperature

31
Q

What is the perfect ionic model

A

It’s spherical shaped with only electrostatic forces of attractions with ionic bonds

32
Q

What causes differences with the theoretical and experimental lattice enthalpies and what is the cause of this

A

When a compound shows covalent character which is caused by polarisation

33
Q

State the type of reaction hydration enthalpies are and what factor cause some elements to have higher hydration enthalpies than others and why

A

They are exothermic reactions

They higher the charge density the greater the hydration enthalpy this id because ions attract water molecules more strongly

34
Q

What causes polarisation

A

The negative ion because distorted and more covalent because of that metal cation causes polarisation

35
Q

What tendencies cause covalent character

A

Small positive ion-because

Positive ion having multiple charges

Negative ion being large meaning outer shell electrons to be less attracted

Negative ions has multiple negative charges

36
Q

State why when a solid dissolves it will be more spontaneous

A

As entropy increases because theirs more disorder

Increases entropy means more particles

This makes G more negative

37
Q

What does this represent

CL2->2Cl

A

Bond disassociation so we divide by 2

38
Q

Why is enthaply hydration exothermic

A

As bonds are made between ions and water which releases energy

39
Q

When will substances have zero entropy

A

When temperature is absolute 0

A Level Chemistry - physical chemistry (8 decks)

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