Entropy Flashcards
Entropy is to do with the?
arrangement and movement of particles
Enthalpy?
the energy involved in chemical bonds
Entropy is made of?
• made up of vibrational, rotational and translational energies (to do w movement)
Entropy is measured as?
• measured as the amount of extra energy of motion (in Joules) that is added per mole of a substance for each degree K the temp rises
Entropy symbol?
• S, standard entropy = S^theta
units for entropy?
JK-1mol-1/ JoulesK-1mol-1
why do metals have a higher entropy than ionic lattice?
metal = delocalised e-s able to move which creates disorder
solids have ? entropy
low - only vibrational energy
gases have ? entropy
high, disordered particles free to move around
why does H2O have a more regular structure?
H bonds
What are the 2 factors that can cause an increase in entropy?
changing state and increasing the number of moles
Why does salt dissolve in water?
• solid is more ordered = low entropy, entropy increases as solid turns into liquid
entropy is all about
disorder
change in entropy=
total of entropy of products - total entropy of reactants
negative entropy means?
amount of disorder has decreased, entropy has decreased
increasing no. of moles =
increased disorder
in entropy calc take into account
no. of moles
entropy & energy?
Less KE = lower entropy
what would happen to entropy at OK?
- Movement of particles stops
* could still be disorder due to arrangement so entropy would be around 0
Change in entropy symbol?
ΔS
What kind of entropy change is favourable?
POSITIVE - more likely to occur
⭐ Entropy definition
The energy of a substance, contained as a result of the movement of particles and arrangement.
⭐ Enthalpy definiton?
the energy of a substance, contained within bonds/ forces
Which reaction is favourable in terms of H?
- exo
- products have lower enthalpy level and, exo reactions have a smaller Ea
- so products = less reactive, more stable than products of endo
What does free energy change do?
- ΔG
- determines whether or not a reacion is feasible by considering ΔS and ΔH
- feasible reaction = one that is likely to take place
- but no indication of how fast a reaction will occur
ΔGθ =
ΔHθ - TΔSθ
ΔGθ & ΔHθ, ΔS units units in the equation?
kJmol-1
Divide ΔS value by 1000 to get kJk-1mol-1
T units?
K - degrees + 273
θ means T =
298K
if ΔG = -
the reaction is feasible
if ΔG = +,
reaction is not feasible
if ΔG = 0
we can rearrange to find the T at which the reaction becomes feasible
T =
ΔH/ ΔS
For ΔH?
Draw Hess’ cycle
in order to get a minus delta G value?
TΔS > ΔH
