Energetics

Question 1

Enthalpy change of reaction

Answer 1

Heat change when molar quantities of reactants as stated in the chemical equation react together

Question 2

Standard enthalpy change of combustion

Answer 2

Energy released when one mole of a substance is completely burnt in oxygen under standard conditions of 298K & 1 bar

Question 3

Standard enthalpy change of Neutralisation

Answer 3

Enthalpy change when one mole of water is formed in the Neutralisation between an acid & an alkali, the reaction being carried out in aqueous solution under standard conditions of 298K & 1 bar

Question 4

Bond energy (of dissociation)

Answer 4

Energy required to break one mole of a covalent bond between two atoms in the gaseous state

Question 5

Standard enthalpy change of for,action

Answer 5

Enthalpy change when one mole of the substance formed from its elements under standard conditions of 298K & 1 bar (elements must be in most stable physical form)

Question 6

Hess’ law

Answer 6

Enthalpy change of a chemical reaction depends only on the final & initial states of the system, & is independent of the reaction pathway taken

Question 7

Standard enthalpy change of hydration… of an ion

Answer 7

Enthalpy change when one mole of the gaseous ions is dissolved in such a large amount of water that addition of more water products produces no further heat change under standard conditions of 298k and 1 bar

Question 8

Standard enthalpy change of solution

Answer 8

Enthalpy change when one mole of a substance is dissolved in such a large volume of solvent that addition of more solvent produces no further heat change under standard conditions of 298k & 1 bar

Question 9

Standard enthalpy change of atomisation

Answer 9

Enthalpy change when one mole of separate gaseous atoms is formed from its element under standard conditions of 298 K and 1 bar

Question 10

Ionisation Energy

Answer 10

energy required to remove one mole of electrons from one
mole of gaseous atoms (or ions) to produce one mole of gaseous cations.

Question 11

Entropy

Answer 11

measure of the disorder of the system. It gives a measure of the extent to which particles and energy are distributed within the system

Question 12

Factors affecting entropy of a system

Answer 12

Temperature, phase, number of particles (especially for gaseous), & mixing of particles