Lattice Enthalpy and Born Haber Cycles Flashcards Preview

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Flashcards in Lattice Enthalpy and Born Haber Cycles Deck (18)
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1
Q

Define standard lattice enthalpy.

A

The enthalpy change when 1 mole of a solid ionic compound is formed from its gaseous ions under standard conditions.
It’s a measure of ionic bond strength.

2
Q

How does ionic charge affect lattice enthalpy?

A

The higher the charge on the ions, the more energy is released when an ionic lattice forms.
More energy released means that the lattice enthalpy will be more negative.

3
Q

How does size affect lattice enthalpy?

A

The smaller the ionic radii of the ions involved, the more exothermic (more negative) the lattice enthalpy. Smaller ions attract more strongly because their charge density is higher.

4
Q

What does Hess’s law state?

A

The total enthalpy change of a reaction is always the same, no matter which route is taken.

5
Q

Enthalpy change of formation ΔHfΘ

A

The enthalpy change when one mole of a compound is formed from its constituent elements in their standard states under standard conditions
Na(s) + ½ Cl2 (g) -> NaCl(s)

6
Q

Standard enthalpy of atomization ΔatHΘ

A

The enthalpy change when 1 mole of gaseous atoms is formed from an element in its standard state.
½ Cl2 (g) → Cl (g)

7
Q

First ionisation energy definition.

A

The energy required to remove the outermost electron from one mole of gaseous atoms to produce 1 mole of gaseous ions each with a charge of 1+.

8
Q

Second ionisation energy

A

The energy required to remove one electron from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions.

9
Q

First electron affinity

A

The enthalpy change accompanying the addition of one electron to each atom in one mole of gaseous atoms to in one mole of gaseous 1- ions
Cl (g) + e- → Cl- (g)

10
Q

Second electron affinity

A

The enthalpy change accompanying the addition of one electron to each ion in one mole of gaseous 1- ions to form one mole of gaseous 2- ions

11
Q

What is lattice enthalpy?

A

Lattice enthalpy is a measure of the strength of the forces between the ions in an ionic solid.

12
Q

Suggest why the second electron affinity of oxygen is positive.

A

“oxide” ion and electron are both negative hence energy is required to overcome repulsion

13
Q

Enthalpy change of solution

A

The enthalpy change when 1 mole of solute is dissolved in sufficient solvent than no further enthalpy change occurs on further dilution.

14
Q

What two things happen when a solid ionic lattice dissolves in water.

A

1) The bonds between the ions break- this is endothermic. The enthalpy change is the opposite of the lattice enthalpy.
2) Bonds between the ions and water are made- this is exothermic. The enthalpy change here is called the enthalpy of hydration.

15
Q

How does ionic charge affect enthalpy of hydration?

A

Ions with a higher charge are better at attracting water molecules than those with lower charges.
More energy is released when the bonds are made giving them a more exothermic enthalpy of hydration.

16
Q

How does the size of ions affect enthalpy of hydration?

A

Smaller ions have a higher charge density than bigger ions.

They attract the water molecules better and have a more exothermic enthalpy of hydration.

17
Q

Enthalpy change of hydration

A

The enthalpy change when 1 mole of aqueous ions is formed from gaseous ions.

18
Q

Equation for percentage yield

A

Actual/ theoretical x 100%