4.1 Energetics Solids And Solutions

Question 1

Lattice Enthalpy

Answer 1

The Enthalpy of one mole of a solid ionic compound is converted to gas phase of its ions

Question 2

Lattice Enthalpy equations

Answer 2

Na2O (s) => 2Na+ (g) + O2- (g)

MgF2(s) => Mg2+(g) + 2F-(g)

Question 3

Group I and Group II Lattice Enthalpies as you move down the group

Answer 3

Lattice enthalpies decrease as the metal ions get bigger and the distance between neighbouring ions increases down the group.

Question 4

Group I and Group II differences

Answer 4

Group II have a significantly higher lattice enthalpy as the ions charge increases resulting is higher attractions between neighbouring ions

Question 5

Standard enthalpy of formation

Answer 5

the enthalpy change when one mole of the compound is formed from its elements under standard condition

Question 6

Formation equations

Answer 6

Mg(s)+ Cl2(g) => MgCl2

Question 7

Formation Equations applying Hess’s law

Answer 7

ΔfHΘ = Δatoms + Δions - ΔlattH

Question 8

ΔlattH has to be endothermic ?

Answer 8

To overcome the attractive forces between oppositely charged ions in the lattice

Question 9

ΔatomH has to endothermic ?

Answer 9

Energy required to break bonds between the atoms

Question 10

ΔionsH has to endothermic ?

Answer 10

Energy needed to ionise the metal atoms is greater than the energy released on adding electrons to the non-metal atoms

Question 11

ΔfH has to move exothermic ?

Answer 11

As energy is released when ions bond to form the lattice is greater than the energy needed to break the bond within the element

Question 12

Enthalpy of atomisation

Answer 12

The enthalpy change when one mole of gas phase atoms are formed from the element in its standard state

Question 13

First electron affinity

Answer 13

The enthalpy change when one mole of electrons is added to one mole of gas phase ions with a charge 1-