Enthalpy Change Definitions

Question 1

Enthalpy change of formation

Answer 1

1 mole of a compound is formed from its elements

Question 2

Enthalpy change of atomisation

Answer 2

ONE mole of GASEOUS atoms is formed from the element

s -> g

Question 3

First ionisation energy

Answer 3

Enthalpy change required to remove ONE electron from EACH atom in ONE mole of gaseous atoms to form ONE mole of gaseous 1+ ions

Question 4

Electron affinity

Answer 4

Enthalpy change that takes place when ONE electron is added to EACH atom in ONE mole of gaseous atoms to form ONE mole of gaseous 1- ions

(Opposite of First ionisation energy)

Question 5

Lattice enthalpy

Answer 5

ONE mole of a SOLID ionic compound is formed from its GASEOUS ions

Question 6

Standard enthalpy change of reaction

Answer 6

Yes

Question 7

Standard enthalpy change of combustion

Answer 7

ONE mole of a compound completely reacts with oxygen

Question 8

Standard enthalpy change of neutralisation

Answer 8

An acid and base react to form ONE mole of water

Question 9

Standard enthalpy change of solution

Answer 9

ONE mole of a solute DISSOLVES in a solvent, hence solution

s + aq -> +aq + -aq

Question 10

Enthalpy change of hydration

Answer 10

Dissolving of GASEOUS ions to form ONE mole of AQUEOUS ions

g + aq -> aq

Question 11

What is entropy?

Answer 11

The dispersal of energy within the chemicals making up the chemical system.

Question 12

What is standard entropy?

Answer 12

The entropy of one mole of a substance under standard conditions.

JK-1mol-1

Always POSITIVE

Question 13

What is the Gibbs equation?

Answer 13

G = #H - T#S

#G = Free energy change
“Overall change in energy during a chemical reaction.”

= the triangle

Question 14

What is feasibility?

Answer 14

Whether a reaction is able to happen and is energetically feasible.