5 ENTHALPY CHANGE

Question 1

Standard enthalpy change of reaction

Answer 1

The enthalpy change when molar quantities of reactants as specified by the chemical equation react to form products at 1 bar and 298 K

Question 2

Standard enthalpy change of formation

Answer 2

The enthalpy change when 1 mole of a substance is formed from its constituent elements in their standard states at 298 K and 1 bar.

Question 3

Standard enthalpy change of combustion

Answer 3

energy released when 1 mole of a substance is completely burnt in excess oxygen at 298 K and 1 bar.

Question 4

Standard enthalpy change of neutralisation

Answer 4

energy released when 1 mole of water is formed in the neutralisation reaction between an acid and a base, at 298 K and 1 bar.

Question 5

Standard enthalpy change of atomisation (for elements)

Answer 5

energy required to form 1 mole of gaseous atoms from the element at 298 K and 1 bar.

Question 6

Standard enthalpy change of atomisation

for compounds

Answer 6

energy required to form gaseous atoms from 1 mole of the compound at 298 K and 1 bar.

Question 7

Bond Energy B.E.

Answer 7

The average energy required to break 1 mole of a covalent bond in the gaseous state

Question 8

1st Ionisation Energy

Answer 8

energy required to remove 1 mole of e from 1 mole of gaseous atoms to form 1 mole of singly charged gaseous cations

Question 9

1st Electron Affinity

Answer 9

enthalpy change when 1 mole of e is added to 1 mole of gaseous atoms to form 1 mole of singly charged gaseous anions.

Question 10

Lattice Energy

Answer 10

energy released when 1 mole of solid ionic compound is formed from constituent gaseous ions

Question 11

Standard enthalpy change of hydration

Answer 11

energy released when 1 mole of gaseous ions is dissolved in an infinite volume of water at 298 K and 1 bar.

Question 12

Standard enthalpy change of solution

Answer 12

enthalpy change when 1 mole of solute is completely dissolved in an infinite volume of solvent at 298 K and 1 bar.