22.4 Entropy Flashcards
Hat is entropy definition
The dispersal of energy within chemicals in a chemical system
In general entripy described the disorder of energy , a measure of it
Units of entropy
J per kelvin per mole
Higher entripy= means more energy dispersed
How are 2 ways to think about what will have more entripy for different states and moles
- how does entripy increase with states/ moles
In general, entripy is like a measure of chaos. Energy has a natural tendency to be more disordered and not conctrated. Thus gases will have a higher entripy value than a solid
- however if there are now more moles of something in products for a reaction, then the way you can order the things are GREATER TOO. As a result it can become more DISORDERED, than ordination before, so entropy also INCREASES
How to show entropy changes and predict if positive or negative
If entripy decreases entripy change is negative and fixed Verca —> delta s
Like we said before, if gas produced more entripy = positive
If more / less moles produced then becomes less random = less entripy = so change is negative
Everything has a standard entripy value, what is standard entripy
The entripy of one mole of the substance under standard conditions
HOW TO WORK PUT ENTROPY CHANGE
Entripy of products x moles - entropy if reactants!
What term is used ti describe if a reaction can actually happen or not
Feasibility = used to describe whether a reaction is able to happen energetically
How can a reaction happen what condition needs to be met
Overall, the products need to have a lower energy then the reactants , otherwise it can’t
This must take into account of both entropy, TEMPERTAURE and enthalpy, both energies
Thus the free energy change equation is used
What is free energy change?
Is the OVERALL energy change in a reaction taking into account the entropy at a TEMPERTAURE and the enthlapy change
What is the GIBBS equation and what must we do to it to use it
Change of free energy (delta G) = change in enthakpy - temp in kelvin x entropy in KJ per kelvin
1) make sure temp is in kelvin
2) make sure entropy is in KLOJOULES PER KELVIN OR IT WINT MATCH UP
How to find change in enthakpy using standard formation energies again
Products - INITAL
What value of change of free energy must it be then for the reaction to be FEASIBLE
Delta G MUST BE LESS THAN 0 or ITS NOT FEASIBLE
Thus how can we work out the minimum temp at which reaction feasible at
Set change in free energy to 0, work out temp, anything higher than that will allow reaction to happen
So thus how can a reaction with enthalpy of soltuon (which is hydration - ionic enthalpy lattice) positive still be able to dissolve at room temrlature?
Because taking into account temp and entropy, the change in free energy is NEGATIVE !
WHAT IS LIMITAION OF FREE ENERGY TO DESCRIBE FESSIBIKITY
Why does it appear some reactions with negative change don’t spontaneously take place
DOESNT TAKE INTO SCCOUNT KINETICS LIKE ACTIVATION ENERGY and RATE OF REAVTION
It might have negative change, but because activation energy so high, only a few particles will undergo based on Boltzmann. Or rate if rscrion so slow
