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Chemistry > Enthalpy And Entropy > Flashcards

Enthalpy And Entropy Flashcards

1
Q

Define lattice enthalpy

A

Enthalpy change when 1 mol of an ionic compound is formed from its gaseous ions under standard conditions

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2
Q

What is lattice enthalpy

A

The energy needed to form ionic bonds

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3
Q

Is lattice enthalpy endothermic or exothermic

A

Exothermic because bonds are formed

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4
Q

Define the standard enthalpy change of formation

A

Enthalpy change when 1 mol of a compound is formed from its constituent elements under standard conditions

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5
Q

Define standard enthalpy change of atomisation

A

Enthalpy change when 1 mol of gaseous atoms form from its constituent elements under standard conditions

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6
Q

Is the enthalpy change of atomisation endothermic or exothermic

A

Endothermic because bonds are broken

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7
Q

Define first ionisation energy

A

Enthalpy change when 1 electron is removed form each atom in one mol of gaseous atoms to form 1 mol of gaseous 1+ ions

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8
Q

Are first ionisation energies exothermic or endothermic

A

Endo because energy needed to overcome attraction of electron to nucleus

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9
Q

Define standard electron affinity

A

Enthalpy change when an electron is added to each atom in 1 mol of gaseous atoms to form 1 mol of gaseous 1- ions

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10
Q

Are standard electron affinities endothermic or exothermic

A

Exothermic

Energy released when electron is attracted to the nucleus

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11
Q

Are successive electron affinities endothermic or exothermic

A

Always endothermic

Energy needed to overcome repulsive force os negetive ion

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12
Q

How do you indirectly fing the lattice enthalpy

A

Using born haber cycles

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13
Q

Define the enthalpy change of solution

A

Enthalpy change when 1 mol of solute dissolves in solvent

Water overcomes ionic bonds

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14
Q

Define the enthalpy change of hydration

A

Enthalpy change when 1 mol of gaseous atoms are dissolved to form 1 mol of aqueous ions

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15
Q

What stages does dissolving involve

A

Breaking of ionic bonds to form gaseous ions

Dissolving of gaseous ions to produce aqueous ions

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16
Q

What does the negetive of the lattice enthalpy mean

A

The energy needed to break the ionic lattice

17
Q

What factors affect lattice enthalpy

A

Ionic radius and charge

18
Q

How does ionic radius affect lattice enthalpy

A

Smaller radius = stronger attraction between ions = more negetive enthalpy

Larger charge density

19
Q

How does ionic charge affect lattice enthalpy

A

Larger charge = stronger attraction between ions = more negetive enthalpy

Larger charge density

20
Q

Why can lattice enthalpy be used to predict melting point

A

More negetive lattice enthalpy stronger bonds= higher melting point

21
Q

Factors affecting enthalpy of hydration

A

Ionic radius and charge

22
Q

How does ionic radius affect enthalpy of hydration

A

Large radius= less attraction between ions and water

Hydration enthalpy is less negetive

23
Q

How does the ionic charge affect enthalpy of hydration

A

Larger charge = Larger attraction between ions and water

More negetive enthalpy

24
Q

How can you predict solubility

A

More negetive enthalpy of solution = more likely to Dissolve

25
Q

Define Entropy

A

Increase in disorder

26
Q

Order the states form least to most Entropy

A

Solid liquid gas

27
Q

What is the value for Entropy at oK

A

O

28
Q

What does negetive and positive Entropy change mean

A

Negetive = more ordered

Positive = less ordered more random

29
Q

What is the sign for the Entropy change from solid to liquid

A

Positive

30
Q

Define Entropy change

A

Entropy one one mole of a substance under standard conditions

31
Q

How is Entropy change calculated

A

Entropy of products - Entropy of reactants

32
Q

What must the value of Entropy change be for a reaction to be feasible

A

> 0

33
Q

Define feasibility

A

Whether a reaction is energetically possible/ spontaneous

34
Q

What is the value for gibbs free energy for a reaction to be feasible and just feasible

A

<0

=0

35
Q

Why might G<0 but not spontaneous

A

Large Ea so slow rate of reaction

Chemistry (28 decks)

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