energetics 2 - lattice energy Flashcards

1
Q

Enthalpy change of formation

A

The standard enthalpy change of formation of a compound is the energy transferred when 1 mole of the compound is formed from its elements under standard conditions (298K and 100kpa), with all reactants and products being in their standard states

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2
Q

Enthalpy of atomisation

A

The enthalpy of atomisation of an element is the enthalpy change when 1 mole of gaseous atoms is formed from the element in its standard state

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3
Q

First lonisation enthalpy

A

The first ionisation enthalpy is the enthalpy change required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous ions with a +1 charge

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4
Q

Second lonisation enthalpy

A

The second ionisation enthalpy is the enthalpy change to remove 1 mole of electrons from one mole of gaseous 1+ ions to produces one mole of gaseous 2+ ions.

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5
Q

First Electron Affinity

A

The first electron affinity is the enthalpy change that occurs when 1 mole of gaseous atoms gain 1 mole of electrons to form 1 mole of gaseous ions with a -1 charge

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6
Q

is the first electron affinity endothermic or exothermic?

A

The first electron affinity is exothermic for atoms that normally form negative ions because the ion is more stable than the atom and there is an attraction between the nucleus and the electron

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7
Q

Second Electron Affinity

A

The second electron affinity is the enthalpy change when one mole of gaseous 1- ions gains one electron per ion to produce gaseous 2- ions

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8
Q

is the second electron affinity exothermic or endothermic?

A

The second electron affinity for oxygen is endothermic because it take energy to overcome the repulsive force between the negative ion and the electron

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9
Q

do first Electron affinity values will become more or less exothermic as you go down Group 7 from chlorine to iodine ?
why?

A

First Electron affinity values will become less exothermic as you go down Group 7 from chlorine to iodine because the atoms get bigger and have more shielding so it becomes less easy to attract electrons to the atom to form the negative ion

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10
Q

Enthalpy of lattice formation

A

The Enthalpy of lattice formation is the standard enthalpy change when 1 mole of an ionic crystal lattice is formed from its constituent ions in gaseous form

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11
Q

The strength of an enthalpy of lattice formation depends on… (2)

A
  1. The sizes of the ions
  2. The charges on the ion
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12
Q

how does the size of the ions affect the strength of a enthalpy of lattice formation?

A

The larger the ions, the less negative the enthalpies of lattice formation (i.e. a weaker lattice). As the ions are larger the charges become further apart and so have a weaker attractive force between them.

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13
Q

how do the charges of the ions affect the strength of a enthalpy of lattice formation?

A

The bigger the charge of the ion, the greater the attraction between the ions so the stronger the lattice enthalpy (more negative values).

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14
Q

lattice enthalpies down a group

A

The lattice enthalpies become less negative down any group. e.g. LiCi, NaCI, KCI, RbCl

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15
Q

Theoretical lattice enthalpies assumes a…

A

perfect ionic model where the ions are 100% ionic and spherical and the attractions are purely electrostatic

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16
Q

When the negative ion becomes distorted and more covalent we say it becomes…The metal cation that causes the… is called… if it… the negative ion.

A
  • polarised
  • polarisation
  • more polarising
  • polarises
17
Q

When 100 % ionic the ions are spherical.
The theoretical and the born Haber lattice enthalpies will be….

A

the same

18
Q

lonic with covalent character, The charge cloud is … The theoretical and the experimental Born Haber lattice enthalpies will…

A
  • distorted
  • differ
19
Q

The polarising power of cation increases when…

A
  • the posive ion has a high charge
  • the positive ion is small
20
Q

The polarisability of an anion depends on… The bigger the ion the more easily it is…

A
  • its size
  • distorted
21
Q

When a compound has some covalent character- it tends towards giant covalent so the lattice is… than if it was 100% ionic. Therefore the born haber value would be… than the theoretical value.

A
  • stronger
  • larger
22
Q

Enthalpy of Hydration

A

Enthalpy change when one mole of gaseous ions become hydrated such that further dilution causes no further heat change

23
Q

Enthalpy of solution

A

The enthalpy of solution is the standard enthalpy change when one mole of an ionic solid dissolves in a large enough amount of water to ensure that the dissolved ions are well separated and do not interact with one another

24
Q

The strength of a enthalpy of lattice formation depends on the following factors…

A
  1. The sizes of the ions
  2. The charges on the ion
25
Q

how does the size of an ion affect the strength of a enthalpy of lattice formation?

A

The larger the ions, the less negative the enthalpies of lattice formation (i.e. a weaker lattice). As the ions are larger the charges become further apart and so have a weaker attractive force between them.

26
Q

how does the charges on an ion affect the strength of a enthalpy of lattice formation?

A

The bigger the charge of the ion, the greater the attraction between the ions so the stronger the lattice enthalpy (more negative values).

27
Q

When an ionic lattice dissolves in water, what happens?

A

When an ionic lattice dissolves in water it involves breaking up the bonds in the lattice and forming new bonds between the metal ions and water molecules.

28
Q

are hydration enthalpies endothermic or exothermic and why?

A

Hydration enthalpies are exothermic as energy is given out as water molecules bond to the metal ions.

29
Q

how does charge density affect the hydration enthalpy?

A

The higher the charge density the greater the hydration enthalpy (e.g. smaller ions or ions with larger charges) as the ions attract the water molecules more strongly.

30
Q

When a solid dissolves into ions does the entropy increase or decrease?

A

When a solid dissolves into ions the entropy increases as there is more disorder as solid changes to solution and number of particles increases

31
Q

For salts where AH solution is exothermic the salt will always dissolve at what temperatures?

A

all temperatures