Unit 10D - Entropy - AP Chemistry

enthalpy

heat energy

ΔH = q/mol = kJ/mol

enthalpic energy can be used to…

break/form chemical bonds and intermolecular forces

entropy

the catch-all term for the rest of the system’s energy, usually referred to as the energy of order

ΔS = J/mol°C = q/T

S values for elements and compounds are always…

positive

S values for aqueous ions are…

either positive or negative

order is reflected by a

-S value

disorder is reflected by. a

+S value

dissolution/dissolving is

entropically favorable

order of entropic favorability of phases

solids < liquids < gases

if a chemical reaction changes the overall amount of “order” in the system when comparing the reactant and product sides of the reaction

there was a change in entropy

increasing the number of moles of a gas on the product side =

less order = entropically favorable

synthesis reactions typically result in..

more order = not entropically favorable

decomposition reactions typically result in..

less order = entropically favorable

spontaneous

-G

non-spontaneous

+G

exothermic

-H

endothermic

+H