Flashcards in Thermodynamics Deck (26):

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## Spontaneous reaction

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Reaction that occurs without outside intervention

No heating, no current, no catalyst

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## Reaction speed

### How fast the reaction occurs

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## Entropy

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A thermodynamic function that increases with the number of energetically equivalent ways to arrange the components of a system to achieve a particular state

S=k*ln(W)

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## The second law of thermodynamics

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Given work in a closed system, the final state will always have less potential energy than the initial state

Everything tends to a point of lowest stored energy

Which means, for any spontaneous process, the entropy of the universe increases

Also that thermal energy cannot travel from a cold area to a warm area

And finally, in any closed system, the entropy of the system will either remain constant or increase, but never decreases

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## State function

### The value depends on the state of the system

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## Entropy (S) by state

### Gas> liquid> solid

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## Entropy of the universe

### ΔHuniv=ΔHsys+ΔHsurr

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## Gibbs free energy

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The amount of work that can be done from the available energy in a system

ΔG= ΔH -T(ΔS)

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## Zeroth law of thermodynamics

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If two systems are each in thermal equilibrium with a third, they are also in thermal equilibrium with each other.

If A=B, and B=C, then A=C

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## First law of thermodynamics

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The increase in internal energy of a closed system is equal to the difference of the heat supplied to the system and the work done by it: ΔU = Q - W

Which means that all energy is conserved, it cannot be created or destroyed, only transfered from one state to another

And by adding heat to the system, you either increase internal energy or you cause work to be done within the system

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## Gibbs free energy from equilibrium constant

### ΔG=-R*T*ln(K)

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## Gibbs free energy from standard cell potential

### ΔG=-n*F*E.cell

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## Enthalpy

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Sum of the internal energy to its pressure and volume

H=E+PV

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## Boltzman equation

### S=k*ln(W)

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## Work from entropy

### Ln(W)=S/k

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## Entropy of a gas

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S=kh*P

Kh- henrys constant

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## Total Gibbs free energy in non-standard conditions

### ΔG=ΔG°+RTln(Q)

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## Surroundings Entropy

### ΔSsurr=-(ΔHsys)/T

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## Heat of reaction (ΔH)

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ΔH=Σ(n)ΔHf{of products}-Σ(n)ΔHf{of reactants}

Otherwise

ΔH=ΔE-w

Or

ΔH=ΔG+T(ΔS)

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## Observing a change in entropy (S)

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See which state has a greater number of possible arrangements

Greater number of reactants/products or a decrease in temperature yields a greater entropy

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## ΔS of Surroundings

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Because the reaction occured, the number of possible arrangements for molecules outside the given system changes

ΔSsurr=-ΔHsys/T

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## Relationships between ΔSsurr and ΔSsys

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One is positive while the other is negative

Differ by the ΔG

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## ΔS of the universe

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ΔSuni=ΔSsurr+ΔSsys

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Thermodynamic properties of spontaneous reactions

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Whenever ΔSuniv (so ΔSsys+ΔSsurr) is positive,

The reaction is spontaneous

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## Third law of thermo dynamics

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As a system approaches absolute zero the entropy of the system approaches a minimum value and it is therefore impossible to reduce any system to absolute zero in a finite series of operations.

The entropy of a perfect crystal of an element in its most stable form tends to zero as the temperature approaches absolute zero.

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