Entropy Flashcards
What is entropy
Measure of dispersal in a system
Eg. No of ways particles can be arranged
Eg. No of ways energy is shared between the particles
What does high disorder mean in terms of entropy
Higher entropy
So a large positive value
What state has the lowest entropy
Solids
Why do different states have different entropy
Solids = vibrate about a fixed position = Low disorder = low entropy Gas = vibrate and move around the volume. In random arrangements ans random movements = high disorder = high entropy
How does the number of particles affect entropy
The more particles there are
The more ways they can be arranged
The more ways energy can be arranged
Increases entropy
What happens to entropy in this reaction:
N2O4 -> 2No2
The number of moles increases on the products
So disorder increases
Increases entropy
Why do substances try to increase their entropy
More disorder leads to them being more energetically stable
Why are some reactions feesible
The product of the reaction has a higher entropy
The increase in entropy increases the change in enthalpy
What happens when a substance reaches its maximum entropy state
It’s thermodynamically stable
Won’t react any further without some energy input
What is the equation for entropy change of a reaction
🔺s = s(p) - s(r)
What values of entropy are mor likely to be feasible
Large positive 🔺s
What are the 3 factors that a reaction depends on to happen
🔺s (entropy)
🔺H (enthalpy)
T (temp)
What is the symbole for free energy
🔺G
What is the equation for free energy
🔺G = 🔺H - (Tx🔺S)
What are the units for 🔺H
Jmol-1
What is the units for🔺s
kJmol-1
If 🔺G is +ve what does that mean in terms of feasibility
It’s not feasible
What does it mean in terms of feasibility if 🔺G = 0
The reaction is on,y just feasible
What is the equation for the temperature when the reaction is ONLY JUST feasible (🔺G = 0)
T = 🔺H/🔺S
Using the equation when is the reaction feasible
🔺H = -ve 🔺S = +ve 🔺G = -ve
Using the equation when is the reaction not feasible
🔺H = +ve 🔺s = -ve 🔺G = +ve
Why, even if the 🔺G is -ve, might the reaction not happen
Might have a really high activation energy
Have a really slow rate = looks like nothing is happening
