Entropy is an important concept in chemistry because it is the basis for predicting the natural ______ of a reaction. Keep in mind, both the entropy of _______ & _______ change as heat produced enters or leaves them.
system and surroundings
If reaction is ________, heat is released into the surrounding and their entropy increases (ΔSsurr > 0). If the reaction is _______, heat leaves the surroundings, so their entropy decreases (ΔSsurr < 0).
To calculate the change in entropy that accompanies a reaction, we need to know the _____ entropies of all the substances taking part; then we calculate the difference between the entropies of the _____ and those of the ______. What is this called?
standard reaction entropy (ΔS°)
Standard reaction entropy is the difference between the stand molar entropies of the ______ and those of the _______ while taking into account the ________ _______. State the formula
ΔS°=ΣnSm°(products) - ΣnSm°(reactants)
Explain ΣnSm°(products), also state expected units
It is a sum of standard molar entropies of products multiplied (respectively) by their stoichiometric coefficients
A process is spontaneous only if the TOTAL change in _____, the sum of the changes in the _____ and _______ is positive. So, we must 1st calculate change in entropy of _______ and then add that change to the change of the ______. This goes in accordance with the second law when we realize it refers to ______ systems
system & surrounding
Equation for calculating total entropy change with regards to spontaneity
ΔStot= ΔS + ΔSsurr meaning, entropy change of system plus entropy change of surrounding
It is critical to understand that a process in which ΔS decreases may be spontaneous, provided that the entropy of the surroundings _______ so much that the ΔStot increases. State an example
freezing of water
In reactions where ΔS decreases but ΔSsurr makes ΔStot positive, like in water, when we try to calculate entropy change of surroundings, we must recognize which 4 steps and state the final equation: *also what is T in?
Surroundings are taken to be large,so their temp remains constant, no matter how much energy is transferred (ΔSsurr=qsurr,rev/T)
The heat that leaves the system enters the surroundings, qsurr=-q
For a system maintained at constant pressure the heat that leaves the system can be equated to the change in enthalpy of the system and we can write q = ΔH & ∴ qsurr=-ΔH
Due large surroundings, any transfer of heat into them will, from their perspective, be so small that it can be regarded as occuring reversibly and hence qsurr,rev=-ΔH
equation: ΔSsurr=-(ΔH/T) or (qsurr,rev/T), T is in Kelvin
The equation ΔSsurr=-(ΔH/T) can be derived when any change takes place in a system maintained at ______ pressure and ______ temperature
ΔHfus=ΔHfreeze True or False
If ΔStot is positive (an increase), the process is ______. If ΔStot is negative (a decrease), the reverse process is ________. If ΔStot = 0, the process has no tendency to proceed in ______ direction
A process produces maximum work if it takes place _______. So wrev is more negative than wirrev, meaning, more energy leaves the system as ______ in wrev. As a result, we can state that qrev should also be _____ than qirrev.
The clausius inequality exists because if you replace qrev with qirrev, ΔS >qirrev. State the Clausius inequality and explain the equality.
ΔS ≥ q/T
The equality would only be valid for reversible processes.
For fully isolated systems, q =__ for any process taking place inside the system. Therefore, ΔS ≥ ___ for any process inside an isolated system. Entropy cannot ______ in isolated systems which is a direct result of the _____ law of thermodynamics. So the entropy of the universe must be steadily ______
Reversible and irreversible paths between two given states of the system leave the surroundings in _____ states. This is because entropy is a state function, the value of ΔS, is ______ for both paths but ΔStot is _______ in both paths because entropy of surroundings is _____ for both paths
Memorize the table
Equation for qsurr under reversible isothermal conditions
How much work is done in free expansion?
ΔS is the same in both ______ & ______ pathways
reversible and irreversible
Does a system at equilibrium go in the reverse or forward direction?
Outside of summing up entropy of the system and of the surrounding, name another concept that can help determine spontaneity of a reaction
Gibbs free energy
Gibbs free energy is defined solely in terms of ______ _______, and so G is a _____ ______. State the formula for both Gibbs free energy and change in Gibbs free energy and also state their given scenarios
G = H - TS (constant temp and constant pressure)
ΔG = ΔH - TΔS (constant temp)
Formula for Gibbs free energy at constant temperature AND pressure. The minus sign in this equation means that as long as temp and press. are constant, a(n) ______ in total entropy corresponds to a(n )______ in Gibbs free energy. As a result, under these conditions, the direction of spontaneous change is the direction of ______ Gibbs free energy.
ΔG = -TΔStotincreasedecreasedecreasing
Use the following table to predict spontaneity and value of Gibbs free energy
At constant temperature and pressure, we know that if ΔG = 0, the system is in _______
State 1 (expected) example of atoms, 3 examples of linear molecules and 3 examples of nonlinear molecules
atoms: argon or other ideal gases (monatomic)
linear molecules: any diatomic molecules, carbon dioxide, ethyne or acetylene
nonlinear molecules: water, methane or benzene
List the Cv,ms and Cp,ms for atoms, linear molecules and non-linear molecules
What is the Cvm of O2 under ideal conditions vs not under ideal conditions?
Under ideal conditions, it behaves naturally like a linear molecule at 5/2R
Under non-ideal conditions it behaves like an atom at 3/2R