20 enthalpy A2

enthalpy change of solution (ΔsolH)

is the enthalpy change that takes place when one mole of a solute dissolves in a solvent.

Na+Cl- (s) + aq → Na+ (aq) + Cl- (aq) endo

enthalpy change of hydration (ΔhydH)

enthalpy change that accompanies the dissolving of gaseous ions in water to form one mole of aqueous ions

Na+ (g) + aq → Na+ (aq)

lattice enthalpy (ΔleH)

formation of 1 mol of ionic lattice from gaseous ions

K+ (g) + Cl- (g) → KCl (s) exo

enthalpy change of atomisation ΔatH

enthalpy change takes place for the formation of one mole of gaseous atoms from the element in its standard state and conditions

Na(s) → Na(g)

½ Cl2 (g) → Cl (g)

endo

electron affinity ΔefH

enthalpy change when one electron is added to each atom in one mole of gaseous atoms to form one mole of gaseous 1- ions

Cl (g) + e- → Cl- (g) endo

enthalpy change of formation ΔfH

enthalpy change when one mol of a compound is formed from its elements (in standard states under standard conditions)

Na (s) + ½ Cl2 (g) → NaCl (s) endo

why can enthalpy of solution be endo and exo?

1. your breaking ionic bonds of the solute

2. then making bonds with aqueous ions and water, with IMFs (can be stronger than ionic)