O - Lattices and Solutions Flashcards
what is a lattice structure?
giant structure
consists of cations and anions
held together by strong electrostatic forces
ionic formula = ratio of cation to anion (determined by charge on ions)
solutions
what must be done for a lattice to disolve in a soluton?
strong electrostatic forces of attraction must be overcome
soltions
what are the electrostatic forces called?
the latice enthalpy
solutions
define ‘lattice enthalpy’:
the energy when one mole of solid is formed from the joining of separate ions
exothermic = bond made
-∆Hle is used when dissoliving ionic solids as bonds are being broken
hydration
what happens to ions once lattice is broken?
left with ions in their gaseous state
they must next be dissolved in solvent
hydration
how do you draw a hydrated chlorine ion?
as cl is a - ion the H+ will point towards the Cl-
hyfration
how do you draw a hydrated Na+ ion?
as Na is a + ion the O- will point towards the cation (Na+)
hydration
what is the process of hydrating ions?
it is the enthalpy of hydration
hydration
define ‘enthalpy of hydration’:
the energy change for the formation of a solution of ions from one mole of gaseous ions
∆Hhyd
REMEMBER BOTH ANION AND CATION ARE HYDRATED SEPARATLY - HAVE THEIR OWN VALUE
solution
how do you calculate the enthalpy of solution?
∆Hhyd(cation) + ∆Hhyd(anion) - ∆Hle
soltions
how do you plot the entalpy change of solution on a graph?
gaseous ion and solvent
solute + solvent
solution
draw out with arrows
solutions
how can you tell if a reaction is feasable or not?
feasable = negative enthalpy of solution
not feasable = positve enthalpy of solution
negative the solution CAN form
positive the solution SHOULDN’T form
