CHM2CH19

• Measure of heat gained or lost.
• H=E+PV

• change in H = positive = endothermic
• change in H = negative = exothermic

change in H = H products - H reactants

• measure of the randomness or disorder of a system
• S = Sum n S products - Sum m S reactants

change in S = S final - S initial

• - increase in temperature
• - increase in volume
• - increase in # of molecules or gas moles
• - gases formed from liquids or solids
• - liquids or solutions formed from solids
• - solid disolved in solid

change G = change H - T (change S)

change G = Sum n G products - Sum m G reactants

• change G = negative = spontaneous
• change G = positve = non spontaneuos
• change G = zero = equilibrium

• H = neg S = pos G = neg
• spontaneous at any temp

• H = pos S = neg G= pos
• non-spontaneous at any temp

• H = neg S= neg : depends on TEMP
• Temp is high: G = pos
• Temp is low: G = neg

G = -RT ln K

G = G standard + RT ln Q

• Energy cannot be created or destroyed.
• The total energy of the universe is constant.

The entropy of the universe increases for spontaneous processes and the entropy of the universe does not change for reversible processes.

The entropy of a pure crystalline substance at absolute zero is zero.