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A level Chemistry OCR A > 22.3 Factors affecting Lattice Enthalpy + Hydration > Flashcards

22.3 Factors affecting Lattice Enthalpy + Hydration Flashcards

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1
Q

What factors affect lattice enthalpy?

A

IONIC RADIUS

IONIC CHARGE

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2
Q

How does ionic radius affect lattice enthalpy?

A

￪ ionic radius

￬ ELECTROSTATIC ATTRACTION between oppositely charged ions in ionic lattice

WEAKER ionic bonds

less ENERGY RELEASED during formation of these bonds

LESS EXOTHERMIC lattice enthalpy

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3
Q

What overall determines lattice enthalpy?

A

IONIC BOND STRENGTH

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4
Q

How does ionic charge affect lattice enthalpy?

A

￪ ionic charge

￪ ELECTROSTATIC ATTRACTION between oppositely charged ions in ionic lattice

STRONGER ionic bonds

more ENERGY RELEASED during formation of these bonds

MORE EXOTHERMIC lattice enthalpy

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5
Q

What factors affect hydration enthalpy?

A

IONIC RADIUS

IONIC CHARGE

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6
Q

What overall determines hydration enthalpy?

A

INTERMOLECULAR BOND STRENGTH

between IONS + H2O

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7
Q

How does ionic radius affect hydration enthalpy?

A

￪ ionic radius

WEAKER PERMANENT DIPOLE between IONS + H2O

less ENERGY RELEASED during formation of these forces

LESS EXOTHERMIC hydration enthalpy

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8
Q

How does ionic charge affect hydration enthalpy?

A

￪ ionic charge

STRONGER PERMANENT DIPOLE between IONS + H2O

more ENERGY RELEASED during formation of these forces

MORE EXOTHERMIC hydration enthalpy

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9
Q

How can lattice enthalpy be an indicator of the melting point of an ionic compound?

A

lattice enthalpy = measure of bond strength

MORE EXOTHERMIC LE

= STRONGER ionic bonds, which require MORE ENERGY to break

= HIGHER m.p

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10
Q

During changes of state of simple covalent molecules, intermolecular forces are overcome.

However, giant ionic lattices have no intermolecular forces, ∴ become molten by…

A

breaking ionic bonds between oppositely charged ions

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11
Q

How can hydration enthalpy be a measure of intermolecular force (permanent dipoles) strength?

A

MORE EXOTHERMIC hyd

= more ENERGY RELEASED during formation of permanent dipoles

= stronger permanent dipoles

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12
Q

What type of intermolecular force is formed between dissociated gaseous ions of the ionic lattice + H2O molecules during hydration enthalpy?

A

permanent dipole

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13
Q

What is lattice enthalpy a measure of?

A

ionic bond strength

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14
Q

What is hydration enthalpy a measure of?

A

intermolecular force strength

between dissociated ions + H2O molecules.

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15
Q

If lattice enthalpy is more exothermic, ionic bonds are ____.

A

stronger.

∵ more energy released during formation, so require more energy to break.

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16
Q

If lattice enthalpy is less exothermic, ionic bonds are ____.

A

weaker.

∵ less energy released during formation, so require less energy to break.

17
Q

Which factors give a more exothermic lattice enthalpy?

A

(factors increasing electrostatic attraction between oppositely charged ions)

smaller ionic radius + greater ionic charge

18
Q

Which factors give a less exothermic lattice enthalpy?

A

(factors decreasing electrostatic attatraction between oppositely charged ions)

larger ionic radius + lower ionic charge

19
Q

Which factors give a more exothermic hydration enthalpy?

A

(factors increasing permanent dipole strength between ions + H2O)

smaller ionic radius + greater ionic charge

20
Q

Which factors give a less exothermic hydration enthalpy?

A

(factors decreasing dipole strength between ions + H2O)

larger ionic radius + lower ionic charge

21
Q

What should the enthalpy of solution be if a substance is soluble in water?

A

exothermic

LE < Δhyd for both ions

22
Q

what should the enthalpy of solution be if a substance is insoluble in water?

A

endothermic

LE > Δhyd for both ions

23
Q

What are ionic liquids?

A

ionic compounds which are liquid below 100°C

24
Q

What are the properties of ionic liquids?

A

Conduct electricity

Do not vaporise easily

Dissolve wide range of substances

A level Chemistry OCR A (44 decks)

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