High Entropy: Can be rearranged in many ways and leave the same structure. Very chaotic/disordered.
Low Entropy: Can be rearranged in very few ways and leave the same structure. Very ordered/regular.
HIGH Gas --> Liquid --> Solid LOW
Entropy change of reaction =
total entropy of products - total entropy of reactants.
Positive and Neagtive Entropy changes
If a change makes a system more random, DeltaS is positive.
If a change makes a system more ordered, DeltaS is negative.
H2 (g) + 1/2O2 (g) --> H2O (l) Sign: -ve
The reactants have gaseous molecules and the product is a liquid. Gas has a higher entropy than liquid, so the product side is more ordered, therefore Delta S is negative.
2C (s) + O2 (g) --> CO2 (g) Sign: +ve
The reactants have more moles of solid than gas. Because the product is a gas, it has less order than the reactants, therefore Delta S is positive.
Enthalpy Change of Solution/Hydration
Enthalpy Change of Solution: The enthalpy change that takes place when one mole of a compound is completely dissolved in water under standard conditions.
Can be an endothermic or an exothermic process (Delta H is positive or negative).
Enthalpy Change of Hydration: The enthalpy change that takes place when one mole of isolated gaseous ions is dissolved in water, forming one mole of aqueous ions under standard conditions.
Hydration is an exothermic process (Delta H is negative).
Addition of NaOH (OH-) to complex Ions.
Cu2+ (aq) + 2OH- (aq) --> Cu(OH)2 (s)
Blue solution --> Blue/Green precipitate
Co2+ (aq) + 2OH- (aq) --> Co(OH)2 (s)
Dark red/pink solution --> Dark blue precipitate (Beige in presence of air)
Fe2+ (aq) + 2OH- (aq) --> Fe(OH)2 (s)
Pale Green solution --> Dark green precipitate
Fe3+(aq) + 3OH- (aq) --> Fe(OH)3 (s)
Dark Orange solution --> Rusty Brown precipitate
Ligand Substitution colour changes.
Copper (II) Sulphate + Ammonia:
Blue solution--> Light Blue Precipitate --> Dark Blue Solution
Copper (II) Sulphate + HCL:
Blue solution --> Yellow Solution
Cobalt (II) Chloride + HCL:
Dark red/pink solution --> Dark Blue/ Purple solution