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Physical Chemistry Year 2 > thermodynamics > Flashcards

thermodynamics Flashcards

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1
Q

What does Hess’ law state

A

the enthalpy change of a reaction is independent of the route taken

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2
Q

define standard enthalpy of formation

A

the enthalpy change when one mole of a compound is formed from its constituent elements in standard conditions, with all products and reactants in their standard states

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3
Q

what is the standard enthalpy of an element

A

0

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4
Q

define standard enthalpy of combustion

A

the enthalpy change when one mole of a substance is completely burnt in excess oxygen

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5
Q

define standard enthalpy of atomisation

A

enthalpy change when one mole of gaseous atoms is formed from a compound in its standard state in standard conditions

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6
Q

define first ionisation energy

A

enthalpy change when one mole of electrons is removed from one mole of gaseous atoms to form one mole of gaseous 1+ ions

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7
Q

define second ionisation energy

A

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

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8
Q

define first electron affinity

A

enthalpy change when one mole of gaseous atoms gain one mole of electrons to form one mole of gaseous 1- ions

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9
Q

define second electron affinity

A

enthalpy change when one mole of gaseous 1- ions gains one mole of electrons to form one mole of gaseous 2- ions.

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10
Q

define lattice enthalpy of formation

A

enthalpy change when one mole of solid ionic lattice is formed from its constituent gaseous ions.

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11
Q

define lattice enthalpy of dissociation

A

enthalpy change when one mole of solid ionic lattice is dissociated into its gaseous ions

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12
Q

define enthalpy of hydration

A

enthalpy change when one mole of gaseous ions become hydrated/dissolved in water to infinite dilution

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13
Q

define enthalpy of solution

A

enthalpy change when one mole of solute dissolves completely in a solvent to infinite dilution.

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14
Q

define mean bond dissociation enthalpy

A

enthalpy change when one mole of covalent bonds is broken, with all species in the gaseous state

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15
Q

what is a born haber cycle

A

thermochemical cycle showing all the enthalpy changes involved in the formation of an ionic compound. start with elements in their standard state.

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16
Q

what factors affect the lattice enthalpy of an ionic compound

A

size of the ion

charge of the ion

17
Q

how can you increase the lattice enthalpy

A

smaller ion

charge centres will be closer together increasing the charge. increased electrostatic forces of attraction.

18
Q

how can born haber cycles be used to see if compounds could theoretically exists

A

use known data to predict certain values and then see if these compounds would be thermodynamically stable.

19
Q

what happens when a solid is dissolved in terms of interactions of the ions with water

A

break lattice
gaseous ion, dissolve
surrounded by water

20
Q

what is the perfect ionic model

A

perfectly spherical
even charge distribution
no covalent character

21
Q

what kind of bonds will be the most ionic

A

between large positive ions and small negative ions

22
Q

define spontaneous and feasible

A

it will take place of its own accord

23
Q

is a reaction with a positive or negative enthalpy change more likely to be spontaneous

A

negative

24
Q

define entropy

A

randomness of a system

25
Q

units of entropy

A

JK-1mol-1

26
Q

what is the second law of thermodynamics

A

entropy always increases, as it is overwhelmingly more likely for molecules to be disordered than ordered

27
Q

is a reaction with positive or negative entropy change more likely to be spontaneous

A

positive

28
Q

compare the general entropy for solids, liquids and gases

A

solids < liquids < gases

29
Q

how do you calculate the entropy change for a reaction

A

sum of products entropy - sum of reactants entropy

30
Q

gibbs free energy

A

delta G = delta H - Tdelta S

31
Q

what does gibbs free energy show

A

if delta G < / = 0 then the reaction is feasible

32
Q

why is entropy 0 at 0K

A

no disorder

Physical Chemistry Year 2 (5 decks)

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