AP Chemistry 12 Energy Relationships in Chemistry.

Slides:



Advertisements
Similar presentations
Energy and Chemical Reactions Energy is transferred during chemical and physical changes, most commonly in the form of heat.
Advertisements

International Baccalaureate Chemistry
Chapter 5 “Thermochemistry”
Solid Liquid Gas MeltingVaporization Condensation Freezing.
Work, Heat and Internal Energy: The First Law. System – the specific part of the universe of interest to us Surroundings – the part of the universe not.
Thermochemistry Chapter 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter 5 Thermochemistry
Prentice Hall © 2003Chapter 5 Chapter 5 Thermochemistry CHEMISTRY The Central Science 9th Edition David P. White.
Chapter 5 Thermochemistry
6–16–1 Ch. 6 Thermochemistry The relationship between chemistry and energy Basic concept of thermodynamics Energy conversion: Energy: the capacity to do.
Energy Relationships in Chemical Reactions
Prentice-Hall © 2007 General Chemistry: Chapter 7 Slide 1 of 58 CHEMISTRY Ninth Edition GENERAL Principles and Modern Applications Petrucci Harwood Herring.
Energy and Heat.
Energy Relationships in Chemistry
Chapter 51 Chapter 6 Thermochemistry Jozsef Devenyi Department of Chemistry, UTM.
Energy Transformations Thermochemistry is the study of energy changes that occur during chemical reactions and changes in state. The energy stored in the.
Thermochemistry Chapter 6 AP Chemistry Seneca Valley SHS.
CHEMISTRY Matter and Change
Chapter 17 Thermochemistry
AP Chapter 5 Thermochemistry HW:
Energy, Enthalpy Calorimetry & Thermochemistry
Unit 13: Thermochemistry Chapter 17 By: Jennie Borders.
Chapter 5 Thermochemistry
Energy and Chemical Reactions
Thermochemistry. Kinetic Energy and Potential Energy Kinetic energy is the energy of motion: Potential energy is the energy an object possesses by virtue.
Thermochemistry Chapter 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
General Chemistry M. R. Naimi-Jamal Faculty of Chemistry Iran University of Science & Technology.
Prentice-Hall © 2002General Chemistry: Chapter 7Slide 1 of 50 Chapter 7: Thermochemistry Philip Dutton University of Windsor, Canada Prentice-Hall © 2002.
Chapter 5: Thermochemistry. Thermochemistry: – Energy Kinetic & Potential – First Law of Thermo internal energy, heat & work endothermic & exothermic.
CHM 108 SUROVIEC SPRING 2014 Chapter 6 Energy Transfer.
Thermochemistry © 2009, Prentice-Hall, Inc. Chapter 16 Thermochemistry.
Thermochemistry ENERGY CHANGES.. Energy is the capacity to do work Thermal energy is the energy associated with the random motion of atoms and molecules.
Thermochemistry Chapter 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Unit 13: Thermochemistry Chapter 17 By: Jennie Borders.
Chapter 5: thermochemistry By Keyana Porter Period 2 AP Chemistry.
Thermochemistry! AP Chapter 5. Temperature vs. Heat Temperature is the average kinetic energy of the particles in a substance. Heat is the energy that.
Thermochemistry. n Thermochemistry is the study of _________________ during chemical reactions.
Good Morning 11/16/2015 Today we will be working on the notes for ch 11.
Thermochemistry © 2009, Prentice-Hall, Inc. Chapter 11 Thermochemistry.
Thermochemistry Chapter 5 Thermochemistry. Thermochemistry Energy The ability to do work or transfer heat.  Work: Energy used to cause an object that.
Chapter 15 Energy and Chemical Change Energy Energy can change for and flow, but it is always conserved.
Thermochemistry Chapter 6 Dr. Ali Bumajdad.
Thermochemistry Chapter 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Thermal Chemistry. V.B.3 a.Explain the law of conservation of energy in chemical reactions b.Describe the concept of heat and explain the difference between.
Energy and Chemical Reactions Energy is transferred during chemical and physical changes, most commonly in the form of heat.
Chapter 5 Thermochemistry. Energy Energy is the ability to do work or transfer heat. –Energy used to cause an object that has mass to move is called work.
Chemistry 231 Thermodynamics in Reacting Systems.
Unit 7 Test Review. quantity of heat needed to raise the temperature of 1 g of water by 1 C calorie.
THERMOCHEMISTRY. Definitions #1 Energy: The capacity to do work or produce heat Potential Energy: Energy due to position or composition Kinetic Energy:
Thermochemistry Chapter 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
General Chemistry M. R. Naimi-Jamal Faculty of Chemistry Iran University of Science & Technology.
Thermochemistry Some Like It Hot!!!!!. The Flow of Energy ► Thermochemistry – concerned with heat changes that occur during chemical reactions ► Energy.
Dr. Orlando E. Raola Santa Rosa Junior College
Energy Relationships in Chemical Reactions. The nature of Energy and Types of Energy Energy – The capacity to do work Chemists define work as directed.
Thermochemistry © 2009, Prentice-Hall, Inc. Topic 9 Thermochemistry.
THERMOCHEMISTRY. Thermochemistry Chapter 6 Definitions #1 Energy: The capacity to do work or produce heat Potential Energy: Energy due to position or.
Prentice Hall © 2003Chapter 5 Chapter 5 Thermochemistry CHEMISTRY The Central Science 9th Edition David P. White.
Chapter 11 Thermo chemistry Heat and Chemical Change The Flow of Energy – Heat Measuring and Expressing Heat Changes Heat in Changes of State Calculating.
Thermochemistry Energy and Chemical Change. Energy Energy can change for and flow, but it is always conserved.
TO LIVE IS THE RAREST THING IN THE WORLD. MOST JUST EXIST. THAT IS ALL.
Thermochemistry © 2009, Prentice-Hall, Inc. Thermochemistry.
Chapter 15 Energy and Chemical Change Section 15.1 Energy Section 15.2Heat Section 15.3Thermochemical Equations Section 15.4 Calculating Enthalpy Change.
Energy and Chemical Reactions Energy is transferred during chemical and physical changes, most commonly in the form of heat.
Thermochemistry Thermo = heat Chemistry = study of matter.
Thermochemistry Chapter 6
Thermochemistry ENERGY CHANGES ..
Thermochemistry Chapter 6
Thermochemistry Chapter 6
Presentation transcript:

AP Chemistry 12 Energy Relationships in Chemistry

Thermochemistry Thermodynamics – the study of energy and its transformations. Thermochemical changes – energy changes associated with chemical reactions. System  that specify part of the universe of interest to us. Surroundings  the part of the universe not contained in the system.

3 types of Systems open system  exchanges mass and energy closed system  exchanges energy but no mass isolated system  no exchange of either mass or energy

Three Types of Systems Open system Closed System cork Isolated System insulation

Different Types of Energy Energy – the ability to do work. Thermal energy – associated with the random motions of atoms and molecules Heat energy – transfer of thermal energy between two objects at different temperature.

Energy (cont’d) Chemical energy – energy stored within the structural units of chemical substance. Potential energy – the ability of an object to do work because of its position in a field of force.

Kinetic Energy – the work that can be performed by a moving object. The unit of energy 1 Joule (J) =1 kg m 2 /s 2 An older unit of energy 1 calorie (cal) = J exactly

The Law of Conservation of Energy The law of conservation of energy  Energy is neither created nor destroyed in ordinary chemical and physical processes.  Converted from one type into another.

This is also stated in terms of the first law of thermodynamics.  E = internal energy change of the system E f and E i  the energy of the final and initial states, respectively

First Law of Thermodynamics Chemical reactions either absorb or release energy. Two terms  Exothermic reaction  heat is released to the surroundings.  Endothermic reaction  heat is supplied to the system by the surroundings.

Exothermic

Endothermic

The First Law Restated chemical systems – examine the conversion of heat energy into work.

Signs for Heat and Work Work done by system on surroundings  w ‘-’ Work done by surroundings on system  w ‘+’ q < 0, heat flows to surroundings  Exothermic ‘-’ q > 0, heat flows to system  Endothermic ‘+’

State and Path Functions  E,  H,  V are examples of state functions.  State functions – numerical value doesn’t depend on how the process is carried out. Work (w) and q (heat) are path functions  The amount of work done or heat released depends on how the system changes states.

Enthalpies of Formation – Standard Reaction Enthalpies The enthalpy change for the reaction  H rxn =  H(products) -  H(reactants) We cannot measure the absolute values of the enthalpies!! How do we ‘measure’ enthalpies (or heat contents) of chemical species?

The Formation Reaction A "chemical thermodynamic reference point." For CO and CO 2 C (s) + O 2 (g)  CO 2 (g) C (s) + ½ O 2 (g)  CO (g) The "formation" of CO and CO 2 from its constituent elements in their standard states under standard conditions.

The Formation Reaction The formation reaction For the formation of 1.00 mole of Na 2 SO 3 (s) 2 Na(s) + S(s) + 3/2 O 2 (g)  Na 2 SO 3 (s) The ‘formation enthalpy of Na 2 SO 3 (s)’, symbolised  H f  [Na 2 SO 3 (s)]

Standard Conditions for Thermodynamic Reactions The degree sign, either  or , indicates standard conditions  P = 1.00 atm  [aqueous species] = 1.00 mol/L  T = temperature of interest (note 25  C or K is used in the tables in your text).

The Significance of the Formation Enthalpy  H f ° is a measurable quantity! Compare CO (g) with CO 2 (g) C (s) + 1/2 O 2 (g)  CO (g)  H f ° [CO(g)] = kJ/mole C (s) + O 2 (g)  CO 2 (g)  H f ° [CO 2 (g)] = kJ/mole The formation enthalpy for CO 2 (g) is larger than the formation enthalpy of CO (g).

Reaction Enthalpies Formation enthalpies – thermodynamic reference point, Formation of the elements from themselves is a null reaction –  H f  (elements) = 0 kJ / mole.

The Combustion of Propane

The General Equation Calculate enthalpy changes from the formation enthalpies as follows. Reverse a reaction, the sign of the enthalpy change for the reaction is reversed. Multiply a reaction by an integer, the enthalpy change is multiplied by the same integer.

The Measurement of Energy Changes – Calorimetry Calorimetry – the measurement of heat and energy changes in chemical and physical processes. Heat capacity (C) – the amount of heat (energy) needed to raise the temperature of a given mass of substance by 1°C. Specific heat capacity (s) – the amount of heat energy (in Joules, J) required to raise 1 g of a substance by 1°C (units = J/g °C).

General expression for heat capacity C = m s  m is the mass of the substance (in grams). Molar heat capacity C m = M s  M – molar mass of the substance  s – its specific heat capacity.

The Calorimeter A calorimeter – a device which contains water and/or another substance with a known capacity for absorbing energy (heat). Calorimeters are adiabatic systems. All energy changes take place within the calorimeter.

Adiabatic System Adiabatic system – thermally insulated from the rest of the universe No heat exchange between system and surroundings! For an adiabatic system, q total = q rxn + q H 2 O + q cal = 0  -q rxn = q H 2 O + q cal

The Constant Volume (Bomb) Calorimeter  E = q v

The Constant Pressure Calorimeter  H = q p

Other important Enthalpy changes Many other important processes have associated enthalpy changes. The measurement of the heat changes for these process can give us some insight into the changes in intermolecular forces that occur during the transformation.

Heat of dilution and solution.  H sol = the heat absorbed or given off when a quantity of solute is dissolved in a solvent.  H sol = H(sol’n) - H(component)  H(component) = H (solid) + H(solvent)

For the process, HCl (aq, 6 M)  HCl (aq, 1 M). A significant amount of heat is released when the acid solution is diluted. This is the enthalpy of dilution of the acid.  H dil = H(sol’n 2) – H(sol’n,1)

Lattice Enthalpies Look at the following process. NaCl (s)  Na + (g) + Cl - (g)  H =  H lat = 788 kJ/mole  the lattice enthalpy A very endothermic reaction! Due to the strength of the ionic bond!

Latent Heats Latent heats are the enthalpy changes associated with phase transitions. H 2 O (l)  H 2 O (g)  H r =  H vap  the enthalpy of vapourization. H 2 O (s)  H 2 O (l)  H r =  H fus  the enthalpy of fusion. H 2 O (s)  H 2 O (g)  H r =  H sub  the enthalpy of sublimation.

Latent Heats

Foods and Fuels Most of the chemical reactions that produce heat are combustion reactions. Note – all combustion reactions are exothermic. Fuel values are generally reported as positive quantities. Obtaining fuel values – calorimetry.

Fossil Fuels Coal, petroleum, and natural gas are known as fossil fuels. They are collectively the major source of energy for commercial and personal consumption. Fossil fuels are mixtures of many different kinds of organic compounds. The fuel values of fossil fuels is directly related to the amount of carbon and hydrogen in the fuel.

Hydrogen As a Fuel Hydrogen has a huge fuel value (142 kJ/g). The combustion product is innocuous – water. Obviously, there are problems! Two major difficulties with H 2 as a fuel source.  Where do we get the hydrogen?  How do we store the hydrogen?