O - Lattices and Solutions

Question 1

what is a lattice structure?

Answer 1

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)

Question 2

solutions

what must be done for a lattice to disolve in a soluton?

Answer 2

strong electrostatic forces of attraction must be overcome

Question 3

soltions

what are the electrostatic forces called?

Answer 3

the latice enthalpy

Question 4

solutions

define ‘lattice enthalpy’:

Answer 4

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

Question 5

hydration

what happens to ions once lattice is broken?

Answer 5

left with ions in their gaseous state
they must next be dissolved in solvent

Question 6

hydration

how do you draw a hydrated chlorine ion?

Answer 6

as cl is a - ion the H+ will point towards the Cl-

Question 7

hyfration

how do you draw a hydrated Na+ ion?

Answer 7

as Na is a + ion the O- will point towards the cation (Na+)

Question 8

hydration

what is the process of hydrating ions?

Answer 8

it is the enthalpy of hydration

Question 9

hydration

define ‘enthalpy of hydration’:

Answer 9

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

Question 10

solution

how do you calculate the enthalpy of solution?

Answer 10

∆Hhyd(cation) + ∆Hhyd(anion) - ∆Hle

Question 11

soltions

how do you plot the entalpy change of solution on a graph?

Answer 11

gaseous ion and solvent

solute + solvent

solution

draw out with arrows

Question 12

solutions

how can you tell if a reaction is feasable or not?

Answer 12

feasable = negative enthalpy of solution
not feasable = positve enthalpy of solution

negative the solution CAN form
positive the solution SHOULDN’T form