Enthalpy 2 and Lattice Enthalpy

lattice enthalpy (of formation)

the enthalpy change that occurs when one mole of a compound is formed from its gaseous ions under standard conditions of 298K and 1 atm

first electron affinity

the enthalpy change that occurs when one mole of gaseous atoms gain one mole of electrons to form uninegative ions

first ionisation energy

the enthalpy change when one mole of electrons is removed from one mole of gaseous atoms to form unipositive ions

enthalpy of atomisation

the enthalpy change when one mole of gaseous covalent bonds is broken to form gaseous atoms (endothermic)

bond enthalpy

the enthalpy change when one mole of gaseous atoms is formed from from its elements in its standard state

standard enthalpy of formation

the enthalpy change that takes place when one mole of a compound is formed from its elements under standard conditions, with all reactants and products in their standard states

1st I.E. - endo or exo?

endothermic because energy is required to overcome the attraction between a negative electron and the positive nucleus

1st E.A - endo or exo?

exothermic because the electrons being added are attracted towards the nucleus

2nd E.A - endo or exo?

endothermic, because a second electron is being gained by a negative ion, which repels it, so energy must be put in to force the negative electron onto the negative ion

equation example for lattice enthalpy for formation of KCl (s)

K⁺(g) + Cl⁻(g) → KCl (s)

Lattice enthalpy - endo or exo?

exothermic

equation example for enthalpy of formation with NaCl

Na (g) + ½Cl (g) → NaCl (s)

example equation for enthalpy of atomisation for Cl

½Cl (g) → Cl (g)

example equation for enthalpy of atomisation for Na

Na (s) → Na (g)

example equation for first ionisation energy of Na

Na (g) → Na⁺ + e⁻

example equation for first electron affinity for chlorine

Cl (g) + e⁻ → Cl⁻

standard enthalpy change of solution

the enthalpy change that occurs when one mole of a solute dissolves in a solvent

example equation for enthalpy change of solution for NaCl

Na⁺Cl⁻ (s) + aq → Na⁺(aq) + Cl⁻(aq)

standard enthalpy of hydration

the enthalpy change that occurs when one gaseous ions dissolve in water to form one mole of aqueous ions

example equation for enthalpy of hydration of Na⁺

Na⁺(g) + aq → Na⁺(aq)

effect of ionic radius on lattice enthalpy

as ionic radius increases, lattice enthalpy becomes less negative because attraction between ions decreases

effect of ionic charge on lattice enthalpy

as ionic charge increases, lattice enthalpy becomes more negative because attraction between ions increases

effect of ionic radius on hydration

as ionic radius increases, attraction between water molecules and ions decreases and hydration enthalpy becomes less negative

effect of ionic charge on hydration enthalpy

as ionic charge increases, attraction with water molecules increases and hydration enthalpy becomes more negative