Enthalpy changes

Question 1

What are the units for enthalpy changes?

Answer 1

kJ mol -1

Question 2

What are standard conditions?

Answer 2

100 kPa

Stated temp, usually 298K

Question 3

Do exothermic reactions have a positive or negative enthalpy change?

Answer 3

Negative enthalpy change

Question 4

Do endothermic reactions have a positive or negative enthalpy change?

Answer 4

Positive enthalpy change

Question 5

How can lattice enthalpy be defined?

Answer 5

Lattice formation enthalpy

Lattice dissociation enthalpy

Question 6

What is lattice formation enthalpy?

Answer 6

The enthalpy change when 1 mole of a solid ionic compound is formed from it’s gaseous ions

Question 7

What is lattice dissociation enthalpy?

Answer 7

The enthalpy change when 1 mole of a solid ionic compound is completely dissociated into its gaseous ions

Question 8

Is lattice formation negative or positive enthalpy change?

Answer 8

Negative

Question 9

Is lattice dissociation negative or positive enthalpy change?

Answer 9

Positive

Question 10

Define enthalpy change of formation.

Answer 10

The enthalpy change when 1 mole of a compound is formed from its elements in their standard states

Question 11

Define the bond dissociation enthalpy.

Answer 11

The enthalpy change when all of the bonds of the same type in 1 mole of gaseous molecules are broken

Question 12

Define enthalpy change of atomisation of an element.

Answer 12

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

Question 13

Define enthalpy change of atomisation of a compound

Answer 13

The enthalpy change when 1 mole of a compound in its standard state is converted to gaseous atoms

Question 14

Define the first ionisation energy.

Answer 14

The enthalpy change when 1 mole of gaseous +1 ions is formed from 1 mole of gaseous atoms

Question 15

Define the second ionisation energy

Answer 15

The enthalpy change when 1 mole of gaseous 2+ ions is formed from 1 mole of gaseous 1+ ions

Question 16

Define first electron affinity

Answer 16

The enthalpy change when 1 mole of gaseous 1- ions is made from 1 mole of gaseous atoms

Question 17

Define second electron affinity

Answer 17

The enthalpy change when 1 mole of gaseous 2- ions is made from 1 mole of gaseous 1- ions

Question 18

Define enthalpy change of hydration

Answer 18

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

Question 19

Define enthalpy change of solution

Answer 19

The enthalpy change when 1 mole of an ionic substance dissolves in enough solvent to form an infinitely dilute solution

Question 20

What is Cl2(g) -> 2Cl(g) an example of?

Answer 20

Bond dissociation enthalpy

Question 21

What is 1/2 Cl2(g) -> Cl(g) an example of?

Answer 21

Enthalpy change of atomisation of an element

Question 22

What is NaCl(s) -> Na(g) + Cl(g) an example of?

Answer 22

Enthalpy change of atomisation of a compound

Question 23

What is Mg(g) -> Mg+1 (g) + e- an example of?

Answer 23

First ionisation energy

Question 24

What is Mg+1 -> Mg+2 (g) + e- an example of?

Answer 24

Second ionisation energy

Question 25

What is O(g) + e- -> O-(g) an example of?

Answer 25

First electron affinity

Question 26

What is O-(g) +e- -> O2-(g) an example of?

Answer 26

Second electron affinity

Question 27

What is Na (g) -> Na (aq) an example of?

Answer 27

Enthalpy change of hydration

Question 28

What is Ca(s) + Cl2 (g) -> CaCl2(s) an example of?

Answer 28

Enthalpy change of formation