Energetics: definitions

Question 1

define: standard state

Answer 1

the pure substance is at 100kPa and a specified temp(assume 298K), used to refer to the state that the substance exits under standard conditions

Question 2

define: average bond enthalpy

Answer 2

the average amount of energy required to break one mole of covalent bonds, in a gaseous molecule under standard conditions . bond enthalpy is different in different molecules so the average refers to a range of molecules

Question 3

define: standard enthalpy change of combustion ∆HcӨ

Answer 3

the enthalpy change when one mole of a substance is completely burnt in oxygen under standard conditions

Question 4

define: standard enthalpy change of neutralisation ∆HnӨ

Answer 4

the enthalpy change when one mole of H2O molecules are formed when an acid (H+) reacts with an alkali (OhH-) under standard conditions

Question 5

define: standard enthalpy change of formation ∆Hf Ө

Answer 5

the enthalpy change when one mole of the substance is formed from its elements in their standard states under standard conditions, for any element the standard state is 0

Question 6

define: standard enthalpy change of reaction ∆HrӨ

Answer 6

the enthalpy change when molar amounts of reactants as shown in the stoichiometric equation react together under standard conditons give porducts

Question 7

define: first ionisation energy

Answer 7

the miniumum mount of energy required to remove an electron from each atom in one mole of gaseous atoms under standard conditions

Question 8

define: first electron affinity

Answer 8

the enthalpy change when one electron is added to each atom in one mole of gasous atoms under standard conditions

Question 9

define: standard enthalpy change of vaporisation ∆HvapӨ

Answer 9

the energy needed to convert one mole of a liquid to vapour under standard conditions

Question 10

define:standard ethalpy chane of atomisation ∆HatӨ

Answer 10

this is the enthalpy change when one mole of gasous atoms is formed from an element under standard conditions

Question 11

define: standard enthalpy change of hydration ∆HhydӨ

Answer 11

the enthalpy change when one mole of gaseous ions are surrounded by water molecules to form an infinitely dilute solution under standard condtions

Question 12

define: standard enthalpy change of solution ∆HsolӨ

Answer 12

the enthalpy change when one mole of solute dissolved in excess solvent to form a solution of infinite dilution under standard conditions

Question 13

define: standard lattice enthalpy ∆HlattӨ

Answer 13

the enthalpy change when one mole of ionic compound is broken apart into its constituent gaseous ions under standard conditions