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Flashcards in Thermodynamics Deck (26):
0

Spontaneous reaction

Reaction that occurs without outside intervention
No heating, no current, no catalyst

1

Reaction speed

How fast the reaction occurs

2

Entropy

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)

3

The second law of thermodynamics

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

4

State function

The value depends on the state of the system

5

Entropy (S) by state

Gas> liquid> solid

6

Entropy of the universe

ΔHuniv=ΔHsys+ΔHsurr

7

Gibbs free energy

The amount of work that can be done from the available energy in a system
ΔG= ΔH -T(ΔS)

8

Zeroth law of thermodynamics

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

9

First law of thermodynamics

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

10

Gibbs free energy from equilibrium constant

ΔG=-R*T*ln(K)

11

Gibbs free energy from standard cell potential

ΔG=-n*F*E.cell

12

Enthalpy

Sum of the internal energy to its pressure and volume
H=E+PV

13

Boltzman equation

S=k*ln(W)

14

Work from entropy

Ln(W)=S/k

15

Entropy of a gas

S=kh*P

Kh- henrys constant

16

Total Gibbs free energy in non-standard conditions

ΔG=ΔG°+RTln(Q)

17

Surroundings Entropy

ΔSsurr=-(ΔHsys)/T

18

Heat of reaction (ΔH)

ΔH=Σ(n)ΔHf{of products}-Σ(n)ΔHf{of reactants}
Otherwise
ΔH=ΔE-w
Or
ΔH=ΔG+T(ΔS)

19

Observing a change in entropy (S)

See which state has a greater number of possible arrangements
Greater number of reactants/products or a decrease in temperature yields a greater entropy

20

ΔS of Surroundings

Because the reaction occured, the number of possible arrangements for molecules outside the given system changes
ΔSsurr=-ΔHsys/T

21

Relationships between ΔSsurr and ΔSsys

One is positive while the other is negative
Differ by the ΔG

22

ΔS of the universe

ΔSuni=ΔSsurr+ΔSsys

23

Thermodynamic properties of spontaneous reactions

Whenever ΔSuniv (so ΔSsys+ΔSsurr) is positive,
The reaction is spontaneous

24

Third law of thermo dynamics

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.

25

Work

The use of energy to create a force
Given in NewtonMeters, the product of force and displacement or the integral of Force as a function of displacement when graphed against eachother
W=F*Δs=∫F(Δs)