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what is lattice enthalpy?
the enthalpy change when 1 mole of solid is formed by the coming together of separate ions
what is the main enthalpy change that prevents a substance dissolving?
lattice enthalpy
what is the enthallpy change to split up an ionic compound into its ions?
negative lattice enthalpy
is the enthalpy chnage to split up an ionic compound exo or endo thermic?
endothermic, it is positive, requires energy
is lattice enthalpy exo or endothermic? and why?
exothermic as it makes ionic bonds
what is the enthaply change of hydration?
the enthalpy change for the formation of 1 mole of aqueous ions from 1 mole of gaseous ions
what bonds form between ions and molecules of water for it ti dissolve?
ion-diople interactions
is ethalpy change of hydration positive or negative? and why?
negative as hydration is exothermic due to ion-dipole bonds made
what effect does charge density have on the hydration enthalpy?
as charge density increases, there is greater attraction of water molecules so hydration enthalpy becomes more exothermic
what effect does charge density have on lattice enthalpy?
as charge density increases, there is greaer electrostatic attraction between ions so lattice enthalpy becomes more negative
what is a hydrated ion?
an ion with water molecules bound to them
what is the other version of enthalpy of hydration when the solvent isnt water?
enthalpy of solvation
what is the enthalpy change of solution?
the enthalpy change when one mole of an ionic solid becomes aqeous ionswhy
what is the equation for enthalpy chnage of solution?
sum of enthalpy change of hydration - lattice enthalpy
can a negative enthalpy change of solution dissolve?
yes
why can a slightly positiive enthalpy change of solution still dissolve?
due to entropy
what kind of enthalpy change of solution would occur if you dissolved an ionic compound in a non polar solvent?
very large positive
what is entropy?
a measure of the number of ways that molecules and their associated energy (electrons) can be arranged
what are the units of entropy?
JK-1mol-1
what are 2 factors that increase the entropy of a collection of molecules?
the molecules spread out more the energy is shared among more molecules
place solid, liquid and gas in order of increasing enrpoy
soli liquid gas
what would make entropy change of system positive?
if there are more molecules of products than reactants, if more molecules of products are gaseous than the reactants
what is the equation for the total entropy change for a process?
total entropy change = system entropy - surrounding entropy
what is the equation for the entropy change of a system?
entropy of products - entropy of reactants