1. 1 The basic concepts of thermodynamics
Theoretic bases of bioenergetics. Chemical kinetics and biological processes. Electrochemistry.
Plan
1 The basic concepts of thermodynamics
2. First law of thermodynamics. Heat (Q) and Work ( W)
3. Heat capacity
ass. prof. Dmukhalska Ye. B. prepared

2. The branch of science which deals with energy changes in physical and chemical processes is called thermodynamics
Some common terms which are frequently used in the discussion of thermodynamics are:

3. common terms of thermodynamics
System
characterized
Parameter
Condition (state)
characterizes
Process

4. Classification of the thermodynamics systems according to a structure
homogeneous
heterogeneous
KNO3
KNO3
PbI2↓

5. System is a specified part of the universe which is under observation
The remaining portion of the universe which is not a part of the system is called the surroundings
The system is separated by real or imaginary boundaries.

6. Types of Systems ISOLATED Open Close
(a system which can not exchange mass and energy with the surroundings )
Open
Close
CLOSE
A system which can exchange energy but no mass with its surroundings

7. (p, T, C, viscosity, surface tension, vapour pressure)
Parameters
Extensive
(m, V, U, H, G, S, c)
The properties of the system whose value depends upon the amount of substance present in the system
Intensive
(p, T, C, viscosity, surface tension, vapour pressure)
The properties of the system whose value does not depend upon the amount of substance present in the system

8. Process is the change of all or individual parameters of the system during the length of time (the period of time)
Classification
of a process according to the constant parameter of a system are:
Isothermic process – temperature is constant, T=const
Isochoric process – volume is constant V = const.
Isobaric process – pressure of the system is constant, p = const
Adiabatic process – the system is completely isolated from the surroundings. For an adiabatic (Q=0) system of constant mass, ▲U=W

9. Classification of a process according to the releasing energy
Exothermic process is a process that releases energy as heat into its surroundings. We say that in an exothermic process energy is transferred ‘as heat’ to the surroundings. For example: a reaction of neutralization (acid + basic).
Endothermic process is a process in which energy is acquired from its surroundings as heat. Energy is transferred ‘as heat’ from the surroundings into the system. For example: the vaporization of water

10. Classification of a process according to the direction of reaction
Reversible process is a process in which the direction may be reversed at any stage by merely a small change in a variable like temperature, pressure, etc.
Irreversible process is a process which is not reversible. All natural process are irreversible

11. State function (thermodynamic function)
State of a system means the condition of the system , which is described in terms of certain observable (measurable) properties such as temperature (T), pressure (p), volume (V)
State function (thermodynamic function)
Internal energy U [J/mol]
Enthalpy H [kJ/mol] or [kJ]
Entropy S [J/mol K] or [J/K]
Gibbs energy G [J/mol] or [J]
ΔU = Uproducts - Ureactants

12. State function depends only upon the initial and final state of the system and not on the path by which the change from initial to final state is brought about.

13. Internal energy U
It is the sum of different types of energies associated with atoms and molecules such as electronic energy, nuclear energy, chemical bond energy and all type of the internal energy except potential and kinetic energies.

14. Heat (Q) is a form of energy which the system can exchange with the surroundings. If they are at different temperatures, the heat flows from higher temperature to lower temperature. Heat is expressed as Q.

15. Work (W) is said to be performed if the point of application of force is displaced in the direction of the force. It is equal to the distance through which the force acts. There are two main types of work electrical and mechanical. Electrical work is important in systems where reaction takes place between ions. Mechanical work is important specially in systems that contains gases. This is also known as pressure-volume work.

16. The work of the expanded ideal gass
WORK = Force and Distance h F s

17. If the volume of the system changes by a finite quantity from volume V1 to V2, then total work done can be obtained by integrating:
If the gas expands, V2 › V1 and work is done by the system and W is negative (we will use sign positive)
V2‹ V1 and the work is done on the system and W is positive
Note. It may be noted that many books use the opposite sign convention for work!!! (according to the IUPAC recommendation)

18. Enthalpy H Chemical reactions are generally carried out at constant pressure. ΔU gives the change in internal energy at constant volume. To express the energy changes at constant pressure, a new term called enthalpy was used. Enthalpy cannot be directly measured, but changes in it can be.

19. Enthalpy H
A thermodynamic function of a system, equivalent to the sum of the internal energy of the system plus the product of its volume multiplied by the pressure exerted on it by its surroundings.
▲H = ▲U + p▲V

20. The meaning of ▲H and ▲U 1) ▲H = ▲U in solid or liquid systems 2) ▲H >>▲U in gas system

21. The meaning of the state functions in the thermodynamic processes
Heat absorbed by the system = H positive (Q negative
Heat evolved by the system = H negative (Q positive)
The signs of W or Q are related to the internal energy change.
The meaning of the state functions in the thermodynamic processes
Exothermic process
Qv > 0, ▲U < 0
Qp > 0, ▲H < 0
2) Endothermic process
Qv < 0, ▲U > 0
Qp < 0, ▲H > 0

22. The first law of thermodynamics
Energy can neither be created nor destroyed although it may be converted from one form to another.
The given heat for the system spents on the change of the internal energy and producing the work:
Q = ▲U + W
The internal energy of the system can be changed In two ways:
By allowing heat to flow into the system or out of the system
By work done on the system or work done by the system.

23. Determination according to the process:
1) Isochoric process, V-constant
W= p▲V (▲V = V2- V1) = 0
Qv = ▲U;
2) Isobaric process, p-constant
Qp = ▲U + W , Qp = ▲U + p▲V , W=nRT (according Mendeleyev Klapeyron equation V=nRT/P)
Qp = ▲ H
3) Isothermic process, T – constant
▲U = n Cv ▲T = 0
QT = W =nRT lnV2/V1 = nRT lnP1/P2

24. Bomb calorimeter for the determination of change in internal energy
The process is carried out at constant volume, i.e., ΔV=0, then the product PΔV is also zero.
Thus, ΔU=Qv
The subscript v in Qv denotes that volume is kept constant.
Thus, the change in internal energy is equal to heat absorbed or evolved at constant temperature and constant volume

25. Thermochemistry ▲H = ▲U + p▲V ▲H = ▲U + ▲nRT
The study of the energy transferred as heat during the course of chemical reactions.
Thermochemical reactions:
H2(g) + Cl2(g) = 2HCl; ▲ H = -184,6 kJ
1/2 H2(g) + 1/2 Cl2(g) = HCl; ▲ H = -92,3 kJ/mol
▲ H is calculated for 1 mole of product
▲H = ▲U + p▲V
▲H = ▲U + ▲nRT
Energy change at constant P = Energy change at constant V + Change in the number of geseous moles * RT

26. Correlation U і Н:
If υ0, то НU: СаО + СО2 → СаСО3 If υ0, то НU: Na + H2O → NaOH + H2 If υ=0, то Н=U: H2 + Cl2 → 2HCl

27. Calculation of standard enthalpies of reactions
▲ H = ( Sum of the standard enthalpies of formation of products including their stoichiometric coefficients ) – ( Sum of the standard enthalpies of formation of reactants including their stoichiometric coefficients )
For elementary substances Н0298 = 0

29. The Hess’s law Н1 = Н2 + Н3 + Н4
The products
of reaction
Initial reactans
Н2
Н4
Н3
Н1 = Н2 + Н3 + Н4
If the volume or pressure are constant the total amount of evolved or absorbed heat depends only on the nature of the initial reactants and the final products and doesn’t depend on the passing way of reaction.

30. Conclusions from the Hess law
Нc298(the standard enthalpy of combustion) =-Нf298(the standard enthalpy of formation)
2. Н = ΣnНf298(prod.) - ΣnНf298(reactants)
3. Н = ΣnНс298(reactants) - ΣnНс298(prod.)
4.Н3=Н1-Н2
5.Н1=Н3-Н2 1 1 2 3 2 3

31. The standard enthalpy of formation ▲ H2980
is defined as the enthalpy change that takes place when one mole of the product is formed under standart condition.
C + O2 = CO2 ▲ Hf1 - ?
C + ½ O2 = CO ▲ Hf2
CO + ½ O2 = CO2 ▲ Hf3
▲ Hf1 = ▲ Hf2 + ▲ Hf3

32. 1) Heat cannot be transferred from one body to a second body at a higher temperature without producing some other effect.
2) The entropy of a closed system increases with time
3) The entropy of the universe always increases in the course of every spontaneous (natural) change
The second law of thermodynamics introduces the concept of entropy and its relation with spontaneous processes
In an isolated system such as mixing of gases, there is no exchange of energy or matter between the system
And the surroundings. But due to increase in randomness, there is increase entropy ΔS›0

33. Free energy and free energy change
The maximum amount of energy available to a system during a process that can be converted into useful work
It’s denoted by symbol G and is given by
▲G = ▲H - T ▲S
where ▲G is the change of Gibbs energy (free energy)
This equation is called Gibbs equation and is very useful in predicting the spontaneity of a process.
N.B. Gibbs equation exists at constant temperature and pressure

34. Effect of Temperature on Feasibility of a Process
Exothermic reactions
For exothermic reactions ΔH is always negative, and therefore, it is favourable.
b) Endothermic reactions
For exothermic reactions ΔH is positive and always opposes the process.

35. 1) Spontaneous (irreversible) process :
▲ G < 0, ▲S > 0, ▲H < 0
2) Unspontaneous (reversible) process :
▲ G > 0, ▲S < 0, ▲H > 0
3) Equilibrium state
▲ G = 0

36. Ludwig Boltzmann’ equation:
THIRD LAW OF THERMODYNAMICS: the entropy of a perfectly pure crystal at absolute zero T=273 K is zero.
Ludwig Boltzmann’ equation:
S = klnW,
where k is Boltzmann’s constant k= R/Na
k=1.38 *10-23 J/K.
At Т→0: W = 1; S = 0.

37. Thanks for attention