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- 1. Thermodynamics
- 2. Important terms to remember• System• Surrounding• Work done• Heat• Spontaneous process• Non-spontaneous process
- 3. System and SurroundingA system is defined as the part of universe which isunder study and the rest of the universe is know as thesurroundings. System is separated from surroundingsthrough boundaries.
- 4. Heat
- 5. Sign convention for HEAT• Heat is denoted as “q”.• Heat absorbed by the system is “+ve”• Heat transferred from the system is “-ve”.
- 6. Work Pressure= force applied/total area
- 7. Sign convention for work done• Work done is denoted as w• When work is done on the system it is “+ve”.• When work done by the system it is “-ve”.
- 8. First Law of thermodynamics• Energy can neither be created nor destroyed.
- 9. Internal energyThe total amount of energy associated with a fixed amount of a substance under a given set of conditions is referred to as the internal energy of that substance.
- 10. Internal energy changeΔE = E final state – E initial state
- 11. Mathematical expression• Initial internal energy = E1• Heat involved = q• Work done = wNowE2 = E1 + q + wE2 – E1 = q + w ΔE = q + w Q = ΔE +w Q =ΔE + PΔV
- 12. Enthalpy• The sum of internal energy and pressure volume energy of a system, under a particular set of conditions, is referred to as ENTHALPY.• It is denoted as H.• H = E + PV• ΔH = ΔE + PΔV
- 13. Spontaneous / non-spontaneous processSpontaneous processes Non-spontaneous processes
- 14. Spontaneity and Randomness Diffusion of gases Melting of iceThe degree of randomness is known as ENTROPYSpreading of ink in water Evaporation of water
- 15. Second Law of ThermodynamicsIt is impossible to construct a device which operating in a cycle, has thesole effect of extracting heat from a reservoir and performing anequivalent amount of work.It is impossible for a self acting machine, working in a cyclic process andunaided by any external agency to transfer heat from a body at lowertemperature to a body at higher temperature.
- 16. Second Law of ThermodynamicsWhenever a spontaneous process takes place, it isaccompanied by an increase in the total entropy of theuniverse( system and surrounding) Diffusion of gases
- 17. Entropy and spontaneity• Entropy is positive : the process if spontaneous• Entropy change is zero: Equilibrium• Entropy change is negative: non-spontaneous.
- 18. Entropy in various types of systems• Isolated system: ΔS is positive• Open or closed system: ΔS = ΔS system + ΔS surrounding
- 19. Adiabatic change and entropy• For irreversible change: ΔS > q irrev/ T• For reversible change: q= 0 ΔS = 0• During an adiabatic change the entropy of a system increases if the change is irreversible while it remains constant if the change is reversible.
- 20. Entropy change of the universe in a isothermal reversible process• ΔS system= q/T• ΔS surrounding= -q/T• Total change is entropy = 0• This means that in a reversible isothermal process there is no change in the entropy and the entropy of the universe remains constant.
- 21. Entropy change of the universe in an irreversible process• Entropy of universe increases in an irreversible process.
- 22. Thermal death
- 23. Helmholtz free energy• Or work function is represented by A and is defined as: A = E-TS Where E is internal energy T is temperature S is entropy• Change is Helmholtz free energy ΔA = ΔE – T ΔS
- 24. Gibb’s free energy• The maximum amount of energy available to a system during a process for doing useful work under constant temperature and pressure conditions is called Gibb’s free energy. G = H – TS• Change in Gibb’s free energy: ΔG = ΔH – T ΔS
- 25. Relationship between Gibb’s freeenergy and Helmholtz free energy ΔG = ΔA + P ΔV
- 26. Gibb’s free energy and work done Decrease in free energy may be regarded as• ΔA = -w a measure of the net work done by a system• of constantPtemperature and pressure. ΔG = -w + ΔV• - ΔG = w – P ΔV
- 27. Gibb’s free energy and spontaneity• When ΔG is negative : spontaneous• When ΔG is zero: equilibrium• When ΔG is positive: non-spontaneous
- 28. Standard free energy change and equilibrium constant• The standard free energy change is defined as the free energy change for a process for a specified temperature in which the reactants in their standard state are converted to products in their standard state. ΔG 0 = Σ Δ f G 0 products – ΣΔ f G 0 reactants• In terms of equilibrium constant ΔG 0 = - RT log e K
- 29. Home work• For a reaction K = 1.8 x 10-7 at 300 K. What of the value of ΔG 0 at this temperature? R = 8314 J K-1 mol -1• Define the term entropy. How does T delta S determine the spontaneity of a reaction?

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