lattice enthalpy

Question 1

define lattice enthalpy

Answer 1

It is the formation of 1 mole of a solid ionic lattice from its constituent gaseous ions under standard conditions

Question 2

what does a more exothermic lattice enthalpy mean?

Answer 2

more exothermic = stronger ionic bonds

Question 3

why is it not possible to measure lattice enthalpy directly?

Answer 3

it is not possible to form 1 mole of ionic solid from its gaseous ions

Question 4

define enthalpy change of solution

Answer 4

enthalpy change that takes place when 1 mole of a solute is completely dissolved in water under standard conditions

Question 5

define enthalpy change of hydration

Answer 5

the enthalpy change that takes place when dissolving one mole of gaseous ions in water

Question 6

what are the factors that impact the size of lattice enthalpy

Answer 6

• the size of ions involved
• charges on the ions
• ionic bond strength

Question 7

explain which ions have more negative lattice enthalpy values: smaller or larger ions?

Answer 7

• smaller ions
• they have a stronger nuclear attraction
• they have a greater charge density

Question 8

describe hydration

Answer 8

• ionic lattice is broken and the ions become part of the solution
• positive ions get attracted towards slightly negative oxygen and negative ions get attracted towards slightly positive hydrogen

Question 9

what are the factors that impact the magnitude of the enthalpy of hydration

Answer 9

• the size of the ion
• charge of the ions

Question 10

explain why the second ionisation energy of an element may be more exothermic than its first ionisation energy

Answer 10

• the ion is smaller than the atom
• the electrons are closer to the nucleus and feel a bigger nuclear attraction

Question 11

suggest why the second electron affinity of an element may be positive

Answer 11

• both the ion and the electron are negative
• energy is required to overcome the repulsion

Question 12

what type of process is lattice association (formation)

Answer 12

exothermic

Question 13

what type of process is lattice dissociation

Answer 13

endothermic

Question 14

what is the ΔH of formation

Answer 14

the enthalpy change where 1 mole of a compound is formed from its constituent elements

Question 15

what is the ΔH of formation?

Answer 15

the enthalpy change where 1 mole of a compound is formed from its constituent elements

Question 16

what is the enthalpy change of ionisation

Answer 16

the energy change where 1 mole of electrons are removed from 1 mole of gaseous atoms/ions

Question 17

what is the ΔH of atomisation

Answer 17

the enthalpy change where 1 mole of an element in its standard state is atomised to 1 mole of gaseous atoms

Question 18

what is the bond enthalpy

Answer 18

the energy change where 1 mole of a bond type in the gaseous state is broken to give separate atoms

Question 19

what is the ΔH of electron affinity

Answer 19

the energy change where an electron is added to an atom in the gaseous state

Question 20

what is the equation for calculating the enthalpy change of the solution?

Answer 20

ΔH solution = ΔH lattice dissociation + ΔH hydration

Question 21

what does it mean if the ΔH of the solution is positive?

Answer 21

• less likely to be more soluble

Question 22

what does it mean if the ΔH of the solution is negative

Answer 22

• more likely to be more soluble