1. Physical Chemistry I (TKK-2246) 13/14 Semester 2 Instructor: Rama Oktavian Email: rama.oktavian86@gmail.com Office Hr.: M.13-15, Tu. 13-15, W. 13-15, Th. 13-15, F. 09-11

2. Outlines 1. Application of thermodynamics 2. Thermochemistry 3. Standard enthalpy change 4. Hess’ Law

3. Review process calculation for ideal gas change of state

4. Review Adiabatic change process for ideal gas calculation

5. Application of thermodynamics Application of First law thermodynamic In chemical reaction, temperature of system will change Exothermic : heat must flow to the surroundings to restore the system to the initial temperature Endothermic: heat must flow from the surroundings to restore the system to the initial temperature heat of a reaction is the heat withdrawn from the surroundings in the transformation of reactants at T and p to products at the same T and p

6. Application of thermodynamics  Exothermicity – “out of” a system q < 0  Endothermicity – “into” a system q > 0 Energy System Surroundings Energy System Surroundings Copyright © Houghton Mifflin Company.All rights reserved.

7. Application of thermodynamics Example of chemical reaction Consider reaction occurs in constant pressure and there are two steps of change state

8. Application of thermodynamics Example of chemical reaction Step 1 - In the first step, reactants at T and p are transformed adiabatically to products at T' and p The temperature is change and pressure is constant. According to the first law of thermodynamics Since the process is adiabatic,

9. Application of thermodynamics Example of chemical reaction Step 2 - the system is placed in a heat reservoir at the initial tempera­ture T The temperature is change and pressure is constant. According to the first law of thermodynamics

10. Application of thermodynamics Example of chemical reaction Heat of reaction can be calculated as

11. Thermochemistry Thermodynamics – Study of energy movement, relationship between heat, work, and other energy forms Thermochemistry – Study of heat absorbed or removed during chemical reaction occurs Heat of Reaction – The value of heat that is absorbed of removed during reaction process at given temperature A thermochemical equation is the chemical equation for a reaction (including phase labels).

12. Thermochemistry Calculating heat of reaction in different way For any reaction

13. Thermochemistry Calculating heat of reaction in different way For any reaction

14. Thermochemistry Heat of formation Example

15. Thermochemistry Heat of formation Example

16. Thermochemistry Molar enthalpy of compound

17. Thermochemistry Heat of formation

18. Thermochemistry Heat of reaction Heat of reaction calculation based on heat of formation

19. Standard enthalpy changes Standard enthalpy change, ∆H 0, the change in enthalpy for a process in which the initial and final substances are in their standard states: The standard state of a substance at a specified temperature is its pure form at 1 bar the standard state of liquid ethanol at 298 K is pure liquid ethanol at 298 K and 1 bar

20. Standard enthalpy changes Example of standard enthalpy changes the standard enthalpy of vaporization

21. Standard enthalpy changes Example of standard enthalpy changes

22. Standard enthalpy changes Exercise Problem 7.35 (a-i)

23. Hess’ law “The standard enthalpy of an overall reaction is the sum of the standard enthalpies of the individual reactions into which a reaction may be divided” path-independence of the value of ∆ r H 0

24. Hess’ law Example

25. Temperature dependence of reaction enthalpies Calculating heat of reaction at any reaction temperature Differentiating with respect to temperature, we obtain By definition

26. Temperature dependence of reaction enthalpies Calculating heat of reaction at any reaction temperature Integrating, Rearranging

27. Temperature dependence of reaction enthalpies Example Re-Do example 7.6 from Castellan