3.6 Enthalpy Changes 2

Question 1

enthaply of atomisation?

Answer 1

the enthalpy change when 1 mole of gaseous atoms is formed from a compound in its standard state under sc

Question 2

lattice enthalpy of formation??

Answer 2

the enthalpy change when 1 mole of solid ionic compound is formed frm its gaseous constituent ions under sc

Question 3

lattice breaking enthalpy??

Answer 3

the energy req to break apart an ionic lattice into its gaseous constituent ions under sc

Question 4

enthalpy of solution??

Answer 4

the enthalpy change when one mole of an ionic solid is dissolved in a solvent to infinite dilution so ions no longer interact under sc

Question 5

enthalpy of hydration??

Answer 5

the enthalpy change when one mole of aq ions is formed from one mole of gaseous ions

Question 6

what affects the solubility of ionic compounds in water??

Answer 6

the solubility of ionic compounds depends on the balance bet the hydration enthalpy of ions in the compound and the lattice breaking enthalpy of the compound

Question 7

what factors affect enthalpy of hydration??

Answer 7

hydration enthalpy of an ion depends on the amnt of attraction bet ions and water molecules, the bigger the charge and the smaller the ion, the larger the enthalpy of hydration

Question 8

Hess’s law??

Answer 8

the enthalpy change of a rctn is independent of the route taken

Question 9

how can enthalpy change of a soln be calc using an energy cycle??

Answer 9

lattice breaking enthalpy & enthalpy change of hydration used in energy cycle to calc enthalpy change of soln using Hess’s kaw

Question 10

Born-Haber cycle??

Answer 10

lattice enthalpy cant be calc directly so born-haber cycle used to calc lattice enthalpy by applying Hess’s law, by comparing enthaply of formation of the ionic compound to the enthalpy req to make gaseous ions from the elemnt

Question 11

standard enthalpy of formation?

Answer 11

the enthalpy change when 1 mol of a compound is formed from its elements in their standard states in scs

Question 12

1st IE??

Answer 12

the enthalpy change when 1 mole of gaseous atoms forms one mole of gaseous 1+ ions

Question 13

1st EA??

Answer 13

the enthalpy change when 1 mole of gaseous atoms forms one moole of 1- ions

Question 14

what is the perfect ionic model?

Answer 14

the perfect ionic model assumes that all ions are perfectly spherical and that the bonds have no covalent character

Question 15

why are theoretical lattice enthalpies often diff from experimental ones??

Answer 15

theoretical lattice enthalpies use calculations based on a perfect ionic model of lattice, experimental values differ as most ionic compounds have some covalent character, the more polarisation in ionic bond, the more covalent character of compound

Question 16

how does exothermicity/ endothermicity of deltafH act as a qualitative indicator of a compound’s stability?

Answer 16

for an exothermic rctn the prod are more stable than rctnts
for an endothermic rctn the rctns more stable than the prod