Entropy Flashcards
(24 cards)
what is entropy?
ΔS; a measure of the dispersal of energy as a function of temperature in a system
microstates
arrangements of molecules within an observed system
macrostate
the system in which we examine microstates
the more microstates a system has, the ________ the entropy of the system
greater
number of microstates in a given system
n^x
what is meant by “higher entropy”
increased probability of an outcome occurring
2nd law of thermodynamics
the total entropy of a spontaneous system will increase
why is ΔS of the universe ≥ 0?
even if a local system’s entropy decreases, entropy of the universe will stay the same or increase
when liquid freezes, does ΔS increase or decrease?
decreases: less energy in the system means less particle movement and therefore lower ΔS
when NaCl dissolves in H2O, does enthalpy increase or decrease?
ΔS increases
how does temperature affect ΔS?
increasing temperature increases molecular vibrations + rotations, causing more movement; more movement causes an increase in microstates, so an increase in temp means an increase in ΔS
which phase changes increase ΔS?
solid to liquid, liquid to gas, solid to gas
which phase changes decrease ΔS?
gas to liquid, liquid to solid, gas to solid
how does molecular complexity affect ΔS?
more complex molecules vibrate in different ways, thus having more entropy
mixtures usually have _____ entropy than pure substances
higher
net entropy of a solution
ΔS of solution = ΔS of solute + ΔS of solvent
solvent _______ in entropy, solute ________ in entropy, but the net ΔS is an ________
solvent decreases in entropy, solute increases in entropy, but the net ΔS is an increase
an increase in the number of moles in a chemical reaction generally leads to an increase or decrease in entropy?
an increase because of more microstates and molecular arrangements possible
if entropy and volume are directly related…
when volume increases, entropy increases; when volume decreases, entropy decreases (less room for microstates)
if entropy and pressure are indirectly related…
when pressure increases, entropy decreases; when pressure decreases, entropy increases (more room for molecular movement)
how to calculate change in entropy for a system
ΔS = ΣS(products) - ΣS(reactants)
if entropy increases, ΔS of reaction ________
is positive
if entropy decreases, ΔS of reaction ________
is negative
standard molar entropy
in J/mol (K); more complex molecules have more standard entropy
