11 Entropy and Free Energy How to predict if a reaction can occur, given enough time? THERMODYNAMICS How to predict if a reaction can occur at a reasonable.

Slides:



Advertisements
Similar presentations
Jeffrey Mack California State University, Sacramento Chapter 19 Principles of Chemical Reactivity: Entropy and Free Energy.
Advertisements

Chapter 19 Chemical Thermodynamics. Introduction 1 st Law of Thermodynamics: Energy can be neither created nor destroyed. Energy of the Universe is constant.
CHAPTERCHAPTERCHAPTERCHAPTER 19. Under standard conditions — ∆G o sys = ∆H o sys - T∆S o sys free energy = total energy change for system - energy change.
3 Nov 97Entropy & Free Energy (Ch 20)1 CHEMICAL EQUILIBRIUM Chapter 16 equilibrium vs. completed reactions equilibrium constant expressions Reaction quotient.
Thermochemistry “The Quick and Dirty”.  Energy changes accompany every chemical and physical change.  In chemistry heat energy is the form of energy.
A spontaneous reaction (or favourable change) is a change that has a natural tendency to happen under certain conditions. Eg. The oxidation of iron (rust)
Entropy and Free Energy How to predict if a reaction can occur, given enough time? THERMODYNAMICS How to predict if a reaction can occur at a reasonable.
Chapter 19. Overview Spontaneous Processes Entropy Second Law of Thermo. Standard Molar Entropy Gibbs Free Energy Free Energy & Temp. & Equil. Const.
Control of Chemical Reactions. Thermodynamic Control of Reactions Enthalpy Bond Energies – Forming stronger bonds favors reactions. – Molecules with strong.
Second law of Thermodyna mics - 2. If an irreversible process occurs in a closed system, the entropy S of the system always increase; it never decreases.
Entropy and the 2nd Law of Thermodynamics
Chapter 8 Thermochemistry: Chemical Energy
Chemical Thermodynamics Chapter 19 (except 19.7!).
Energy The Nature of Energy Energy: the ability to do work or produce heat Potential energy (store energy): energy due to position or composition.
Energy and Chemical Change
CHM 112 Summer 2007 M. Prushan Chapter 17 Thermodynamics: Entropy, Free Energy, and Equilibrium.
Spontaneity, Entropy, & Free Energy Chapter 16. 1st Law of Thermodynamics The first law of thermodynamics is a statement of the law of conservation of.
1 PRINCIPLES OF REACTIVITY: ENTROPY AND FREE ENERGY.
Chemical Thermodynamics
Chapter 20 Thermodynamics and Equilibrium. Overview First Law of Thermodynamics First Law of Thermodynamics Spontaneous Processes and Entropy Spontaneous.
Ch. 20: Entropy and Free Energy
Chapter 19 – Principles of Reactivity: Entropy and Free Energy Objectives: 1)Describe terms: entropy and spontaneity. 2)Predict whether a process will.
First Law of Thermodynamics-The total amount of energy in the universe is constant. Second Law of Thermodynamics- All real processes occur spontaneously.
Chapter 20: Thermodynamics
Instructor: Dr. Upali Siriwardane Office: CTH 311 Phone Office Hours: M,W, 8:00-9:00 & 11:00-12:00 a.m.; Tu,Th,F.
Chapter 17 Free Energy and Thermodynamics Lesson 1.
Chapter 19 Chemical Thermodynamics HW:
THERMODYNAMICS: ENTROPY, FREE ENERGY, AND EQUILIBRIUM Chapter 17.
18-1 CHEM 102, Fall LA TECH Instructor: Dr. Upali Siriwardane Office: CTH 311 Phone Office Hours: M,W 8:00-9:00.
Aim: What is entropy?.
Gibbs and the Law of Entropy
Thermodynamics 3 Thermodynamics examines the heat and work as well as spontaneity of a reaction. Spontaneity is the notion of whether.
Chapter 19: Chemical Thermodynamics Spontaneous processes… …happen without outside help …are “product favored”
11 Entropy and Free Energy How to predict if a reaction can occur, given enough time? THERMODYNAMICS How to predict if a reaction can occur at a reasonable.
Chapter 17 Free Energy and Thermodynamics. Goals Entropy (S,  S) and spontaneity Free energy;  G,  G o  G, K, product- or reactant-favored Review:
Chapter 20 Thermodynamics and Equilibrium. Overview First Law of Thermodynamics Spontaneous Processes and Entropy –Entropy and the Second Law of Thermodynamics.
First Law of Thermodynamics – Basically the law of conservation of energy energy can be neither created nor destroyed i.e., the energy of the universe.
Chapter 17 Spontaneity, entropy and free energy. Spontaneous l A reaction that will occur without outside intervention. l We need both thermodynamics.
Chapter 19 Spontaneity, entropy and free energy (rev. 11/09/08)
11 © 2006 Brooks/Cole - Thomson Chemistry and Chemical Reactivity 6th Edition John C. Kotz Paul M. Treichel Gabriela C. Weaver CHAPTER 19 Principles of.
Spontaneity. Recap of Enthalpy Describes chemical potential energy stored in matter. Can only measure changes in enthalpy. Enthalpy is arithmetical. –Reverse.
Thermochemistry! AP Chapter 5. Temperature vs. Heat Temperature is the average kinetic energy of the particles in a substance. Heat is the energy that.
Chapter 15 Energy and Chemical Change Energy Energy can change for and flow, but it is always conserved.
SPRING REVIEW PART TWO. PRECIPITATION REACTIONS Chapter 19 Copyright © 1999 by Harcourt Brace & Company All rights reserved. Requests for permission to.
Section 19.1 Entropy and the Three Laws of Thermodynamics
 What is the formula for finding heat?  What are the two units of heat?  The temperature of a sample of iron with a mass of 10.0 g changed from 50.4.
Energy The ability to do work or produce heat The ability to do work or produce heat Potential- Stored energy Potential- Stored energy Energy stored in.
11 Spontaneous Process A process is spontaneous if it occurs without outside intervention, it happens on its own. Spontaneous processes can be fast or.
Solubility Equilibrium. Example 16.8 Calculating Molar Solubility from K sp Calculate the molar solubility of PbCl 2 in pure water. Begin by writing the.
Entropy and Free Energy (Kotz Ch 20) - Lecture #2
Spontaneity. Spontaneous Processes P/C change that occurs with no outside intervention exothermic chemical rxns are spontaneous energy still must be supplied.
Topic: Reaction Spontaneity Do Now:. Spontaneous Processes no outside intervention =physical or chemical change that occurs with no outside intervention.
Energy & Heat Energy – ability to produce heat Heat - energy in the process of flowing from a warmer object to a cooler object. In chemical reactions.
John C. Kotz State University of New York, College at Oneonta John C. Kotz Paul M. Treichel John Townsend Chapter 19 Principles.
Spontaneous Processes and Entropy First Law “Energy can neither be created nor destroyed“. The energy of the universe is constant. Spontaneous Processes.
Chapter 18 Entropy, Free Energy, and Equilibrium Overview: Spontaneity and Entropy Entropy and Probability Second Law of Thermodynamics Free Energy and.
Topic: Reaction Spontaneity Do Now:. Spontaneous Processes no outside intervention =physical or chemical change that occurs with no outside intervention.
Entropy – Randomness & Disorder Mr Nelson
Chemical Thermodynamics First Law of Thermodynamics You will recall from earlier this year that energy cannot be created nor destroyed. Therefore, the.
Entropy By Introduction One property common to spontaneous processes is that the final state is more DISORDERED or RANDOM than the original.
Reaction Spontaneity. 1. Spontaneous Process First Law of Thermodynamics- “Conservation of Energy” – Energy can change form but it cannot be created or.
Thermochemistry Energy and Chemical Change. Energy Energy can change for and flow, but it is always conserved.
Chapter 15 Energy and Chemical Change Section 15.1 Energy Section 15.2Heat Section 15.3Thermochemical Equations Section 15.4 Calculating Enthalpy Change.
Entropy and Free Energy Thermodynamics: the science of energy transfer – Objective: To learn how chemists predict when reactions will be product-favored.
Unit 10: Thermodynamics. Unit 10: Thermodynamics.
Entropy and Free Energy Chapter 17
Entropy and Free Energy
Entropy and Free Energy
Presentation transcript:

11 Entropy and Free Energy How to predict if a reaction can occur, given enough time? THERMODYNAMICS How to predict if a reaction can occur at a reasonable rate? KINETICS

22 Thermodynamics and Kinetics Diamond is thermodynamically favored to convert to graphite, but not kinetically favored. Paper burns — a product-favored reaction. Also kinetically favored once reaction is begun.

33 Spontaneous Reactions In general, spontaneous reactions are exothermic. Fe 2 O 3 (s) + 2 Al(s) ---> 2 Fe(s) + Al 2 O 3 (s) ∆H = kJ

44 Directionality of Reactions Energy Dispersal Exothermic reactions involve a release of stored chemical potential energy to the surroundings. The stored potential energy starts out in a few molecules but is finally dispersed over a great many molecules. The final state—with energy dispersed—is more probable and makes a reaction spontaneous.

55 Spontaneous Reactions But many spontaneous reactions or processes are endothermic or even have ∆H = 0. NH 4 NO 3 (s) + heat ---> NH 4 NO 3 (aq)

66 How probable is it that reactant molecules will react? PROBABILITY suggests that a spontaneous reaction will result in the dispersal *of energy *or of matter * or of energy & matter. Directionality of Reactions

77 Entropy, S One property common to spontaneous processes is that the final state is more DISORDERED or RANDOM than the original. Spontaneity is related to an increase in randomness. The thermodynamic property related to randomness is ENTROPY, S. Reaction of K with water

88 The entropy of liquid water is greater than the entropy of solid water (ice) at 0˚ C.

99 S (gases) > S (liquids) > S (solids) S o (J/Kmol) H 2 O(liq)69.95 H 2 O(gas)188.8 S o (J/Kmol) H 2 O(liq)69.95 H 2 O(gas)188.8 Entropy, S

1010 Entropy Changes for Phase Changes For a phase change, ∆S = q/T where q = heat transferred in phase change For H 2 O (liq) ---> H 2 O(g) ∆H = q = +40,700 J/mol

1111 Entropy and Temperature S increases slightly with T S increases a large amount with phase changes

1212 Why does the entropy of a substance increases with temperature? Entropy, S

1313 Entropies of ionic solids depend on coulombic attractions. S o (J/Kmol) MgO26.9 NaF51.5 S o (J/Kmol) MgO26.9 NaF51.5 Entropy, S Mg 2+ & O 2- Na + & F -

1414 Increase in molecular complexity generally leads to increase in S. Entropy, S

1515 Entropy usually increases when a pure liquid or solid dissolves in a solvent. Entropy, S

1616 Standard Molar Entropies

1717 Consider 2 H 2 (g) + O 2 (g) ---> 2 H 2 O(liq) ∆S o = 2 S o (H 2 O) - [2 S o (H 2 ) + S o (O 2 )] ∆S o = 2 mol (69.9 J/Kmol) - [2 mol (130.7 J/Kmol) + 1 mol (205.3 J/Kmol)] ∆S o = J/K Note that there is a decrease in S because 3 mol of gas give 2 mol of liquid. Calculating ∆S for a Reaction ∆S o =  S o (products) -  S o (reactants)

1818 2nd Law of Thermodynamics A reaction is spontaneous if ∆S for the universe is positive. ∆S universe > 0 for spontaneous process

1919 Dissolving NH 4 NO 3 in water—an entropy driven process. 2nd Law of Thermodynamics

2020

2121 Sublimation Solid gas

2222 Solid liquid gas liquid evaporationmelting