R1.4 Entropy & Spontaneaity Flashcards
(20 cards)
2nd Law of thermodynamics
The total entropy of the universe tends to increase
ΔS(total) = ΔS(system)+ΔS(surroundings) ≥ 0
=> S HAS to increase to be spontaneous based on this
What is the definition of entropy (S) in a system?
The number of possible arrangements of the particles and their energy in a given system
Entropy measures the disorder or chaos within a system.
What happens to entropy when a system becomes more disordered?
Entropy increases
A higher entropy indicates greater disorder and energetic stability.
examples of a process that increases entropy?
- any heat thats added to a system
(thermal decomp, sublimation, melting, boiling)
The formation of CO2 gas increases disorder compared to solid CaCO3.
What is the relationship between entropy and the stability of a system?
An increase in entropy means that the system becomes energetically more stable
Systems favor higher entropy states due to spread out energy.
What determines the feasibility of a reaction?
Enthalpy change and entropy change
These factors are combined in the Gibbs free energy concept.
What is the Gibbs free energy equation?
ΔGꝋ = ΔHreactionꝋ – TΔSsystemꝋ
ΔGꝋ indicates the spontaneity of a reaction.
What are the units of ΔGꝋ?
kJ mol–1
Units for ΔHreactionꝋ are also in kJ mol–1.
WHat do values of G tell us
What do values of G tell us?
When ΔGꝋ is negative (ΔGꝋ ≤ 0) => Spontaneous
When ΔGꝋ is positive => NOT spontaneous
A negative value indicates the reaction is feasible.
What happens to Gibbs free energy as products increase in non-reversible reactions?
- entropy increases so:
=>Gibbs free energy decreases
The reaction moves towards completion.
What is the behavior of Gibbs free energy in reversible reactions as products increase?
Gibbs free energy decreases until equilibrium is reached
At equilibrium, Gibbs free energy is at its lowest.
What does the equilibrium constant (K) indicate?
Whether the products or reactants are favored at equilibrium
It reflects the position of equilibrium for a reaction.
What is the quantitative relationship between standard Gibbs free energy change and the equilibrium constant?
∆Gθ = -RT ln K
This equation helps calculate the equilibrium constant.
How is the reaction quotient (Q) related to Gibbs free energy?
ΔG = ΔGθ + RT ln Q
Q indicates how far a reaction is from equilibrium.
What happens when a reaction reaches equilibrium?
Q = K and ΔG = 0
At this point, there is no net change in the concentration of reactants and products.
Gibbs Free energy
The energy associated with a chemical reaction that can be used to do useful work
Principle of gibbs equation
ΔGꝋ = ΔH(reaction)ꝋ – TΔS(system)ꝋ
* if -G = spontaneous
that means that either
* enthalpy (H) has to be LOW
* entropy (S) has to be HIGH
How to determine if a reaction is spontaneous/will happen?
- rfeer to Gibbs equation
- look at conditions of S(entropy) and H(enthalpy)
- if conditions arent met, look at how T has to be to make -G
when is exothermic spontaneous
at low temp only (since entropy will be negative/decreasing when energy is released)
when is endothermic spontaneous
at high temp (since entropy is positive/increasing when energy is taken in)
