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chemistry > Thermodynamics > Flashcards

Thermodynamics Flashcards

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1
Q

Define enthalpy of formation
Endo or exo

A

Enthalpy change when one mol of a substance is formed from its elements with all substances in their standard states and under standard conditions

Exothermic

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2
Q

Define enthalpy of atomisatuon
Endo or exo

A

Enthalpy chnage when one mol of gaseous atoms are formed from the elements in its standard states under standard conditions

Endothermic

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3
Q

Define bond dissociation enthalpy
Endo or exo

A

Enthalpy chnage to break one mole of a specific bond in the gas phase
Endo

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4
Q

What is the relationship between bde and atomisation for diatomic molecules

A

The bde is half the atomisation
Bde = 2x atomisation

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5
Q

Define enthalpy of first ionisation energy
Endo or exo

A

Enthalpy change when u mole of electrons is removed from I mole of gaseous atoms to form one mole of gaseous ions with +1 charge

Exithermic

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6
Q

Define enthalpy do second ionisation
Endo or exi

A

The enthalpy change when I mole of electrons is removed from one mole of gaseous ions with +1 charge to form one mole gaseous 2+ ions

Endothermic

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7
Q

Define enthalpy of first electron affinity

Endo or exo

A

Enthalpy change when I mole of electrons added to one mole gaseous atoms to form on mole gaseous ions with -1 charge

Exothermic

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8
Q

Define enthalpy of second electron affinity
Exo or Endo

A

Enthalpy change when I mole of electrons is added to one mole of gaseous ions with a -1 charge to form 1 mole of gaseous ions it’s a 2- charge

Endo

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9
Q

Define enthalpy of lattice formation
Endo or exo

A

Enthalpy change when I mole of a solid ionic compound is formed from its gaseous ions

Exo

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10
Q

Define enthalpy of lattice dissociation
Endo or exo

A

Enthalpy when 1 mole of a solid ionic compound is broken down into its gaseous ions

Endo

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11
Q

What is the relationship between enthalpy of lattice formation and enthalpy of lattice dissociation

A

They are the same magnitude just different signs

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12
Q

What 2 factors influence the magnitude of lattice enthalpy

A

Charge of the ion

Size of ion

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13
Q

How does charge of ion affect magnitude of lattice enthalpy

A

Bigger charge means stronger attraction

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14
Q

How does size of ion affect magnitude of lattice enthalpy

A

Bigger ion is weaker attraction

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15
Q

What are 2 assumptions of the perfect ionic model

A

In jons are perfectly spherical
Charge is evenly distributed

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16
Q

What 2 factors increase covalent character in an ionic substance

A

Positive ions - bigger charge density is more covalent character

Negative ions - bigger negative ion more likely to have higher covalent character

17
Q

How does the covalent character in bonds affect the strength

A

More is stronger bonds

18
Q

Define standard enthalpy of solution

A

Enthalpy change when 1 mole of solid ionic compound is dissolve into water to produce aqueous ions

19
Q

Define standard enthalpy hydration

A

Enthalpy change when I mole of gaseous ions is converted to one mole aqueous ions

20
Q

What forces from between negative and positive ions and water when they are hydrated

A

Ion dipole forces

21
Q

What process is enthalpy of hydration and why

A

Exo
Form attraction between ions and water

22
Q

What 2 factors affect magnitude of enthalpy of hydration

A

Charge of ion - bigger is stronger

Size of ion - maker is stronger

23
Q

Hess cycle for enthalpy of solution and hydration

A

Photos

24
Q

What is entropy
Units
Symbol

A

A measure of disorder
S
J/k

25
Q

Standard conditions for measuring entropy

A

100kpa
298k

26
Q

How do you calculate entropy change

A

Sum fo entropy products - sum of entire reactants

27
Q

What is a feasible reaction

A

A spontaneous recation occurring

28
Q

Gibbs free energy equation

A

Delta g = delta H - t x delta s

29
Q

Units for Gibbs freee

A

Kj / mol

30
Q

How to convert from j/k to kj/k

A

Divide by 1000

Convert before doing equation

31
Q

Negative enthalpy
Positive entropy
Name effect on g
What is graph like

A

Feasible at all temperatures

Photo

32
Q

Positive enthalpy
Negative entropy
Effect on Gibbs
Graph

A

Reaction never feasible at any temperature

33
Q

Positive entropy
Positive enthalpy
Effect on Gibbs
Graph

A

Reaching feasible at high temperatures

34
Q

Negative enthalpy
Negative entropy
Effect on g
Graph

A

Reaction feasible at low temperatures

35
Q

Gibbs free energy equation as equation of straight line

A

Delta g is why

T is x

-delta s is gradient

Delta h is y intercept

36
Q

What does the value it crosses x axis mean

A

temperature reaction ether starts or stops being feasible

chemistry (23 decks)

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