Thermochemistry Definitions

Question 1

Standard enthalpy change of reaction? ΔH

Answer 1

Standard enthalpy change of reaction is the amount of energy absorbed or released in a chemical reaction when the molar quantities stated in the chemical equation react under standard conditions

Question 2

Standard enthalpy change of combustion? ΔHc

Answer 2

Standard enthalpy change of combustion is the energy released when 1 mole of compound is completely burnt in oxygen under standard conditions

Question 3

Standard enthalpy change of neutralisation?

Answer 3

Standard enthalpy change of neutralisation is the energy released when an acid and base react to form 1 mole of water under standard conditions

Question 4

Standard enthalpy change of formation?

Answer 4

Standard enthalpy of formation of the energy change when 1 mole of substance is formed from its elements under standard conditions.

Question 5

Standard enthalpy change of atomisation?

Answer 5

Standard enthalpy change atomisation is the energy absorbed when 1 mole of gaseous atom is formed from the element in its standard state under standard condtions.

Question 6

Standard enthalpy change of atomisation? (Compounds)

Answer 6

Standard enthalpy change of atomisation of a compound is the energy absorbed when 1 mole of compound in a given state is being broken down into its constituent gaseous atoms under standard conditions
SiH4 -> Si(g) + 4H(g)

Question 7

Bond energy?

Answer 7

Bond energy of a covalent bond is the average energy absorbed to break 1 mole of the covalent bond in the gas phase into its constituent gaseous atoms under standard conditions
1 Cl-Cl -> 2Cl

Question 8

Lattice energy?

Answer 8

Lattice energy of an ionic compound is the energy released when 1 mole of the ionic compound is formed from its constituent gaseous ions under standard conditions
Na+ (g) + Cl-(g) -> NaCl (s)