Chem Unit 4

First Law of Thermodynamics

• Energy cannot be created nor destroyed

Second Law of Thermodynamics

• Entropy always increases in the transformation of energy

Third Law of Thermodynamics 

• Entropy for pure crystals at absolute zero is zero.

Spontaneous reaction 

• One that will occur on its own without any external intervention in the direction stated 

 Entropy 

• A measure of the amount of randomness or disorder in a system 

Increases when - temperature increases -molecular complexity increases

S(total) = S(system) + S(surrounding)

S(system) = nProducts - mReactants  (n and m are number of moles)

S(surrounding) = - H/T

Hsolution = Hhyd - Hlatt

Enthalpy of SOLUTION

• Enthalpy change when 1 mole of the compund dissolves in a stated amount of water under standard conditions ( Solid --> aqeous ions)

Lattice Energy

• Enthalpy change when 1 mole of an ionic solid is formed from its gaseous ions under standard conditions (gaseous ions ---> solid)

Enthalpy of Hydration

• Energy realeased when 1 mole of gaseous ions dissolve in water under standard conditions to produce a solution of conc 1 mol dm-3 ( gaseous ---> solution)