Thermodynamics

what is thermodynamics?

the branch of chemistry and physics that studies the transfer of energy accompanying physical and chemical processes

what are the 3 laws of thermodynamics?

1. law of conservation of energy

2. the universe tends to move towards a state of greater entropy (disorder) in spontaneous processes

3. the entropy of a hypothetical pure, perfect crystalline substance at absolute zero has been assigned a value of zero

what is a spontaneous process and what are the two parts of spontaneity?

a change for which the collection of products is thermodynamically more stable than the collection of reactants, under given conditions. the two parts are ∆H and ∆S

what is enthalpy and what is the symbol for standard enthalpy change of reaction?

the heat content of a specific amount of a substance; ∆H

what is entropy and what is the symbol for a standard entropy change of reaction?

a measure of the degree of disorder or randomness of a system; ∆S

what is the difference between the standard molar heat of formation and standard molar heat of reaction?

∆Hf: formation for 1 mole of substance

∆Hrxn: used for balanced equations

what is Hess’s Law?

the enthalpy change for a reaction is the same whether it occurs in one step or series of steps

what is ∆G at equilibrium, spontaneous, and nonspontaneous?

0, negative, positive

-∆H and -∆S

spontaneous below a definite temperature

-∆H and +∆S

spontaneous at all conditions of temperature and pressure

+∆H and -∆S

nonspontaneous at all temperatures

+∆H and +∆S

spontaneous above a definite temperature