State Function revisited….State Function revisited….  Dependent ONLY on a system’s state at a given moment in time.  Only initial and final states 

Slides:

Advertisements

Similar presentations

Stoichiometry of Chemical Equations and Formulas.

Advertisements

Slide 1 of The First Law of Thermodynamics  Internal Energy, U.  Total energy (potential and kinetic) in a system. Translational kinetic energy.

Thermochemistry Chapter 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Lecture 4: Standard Enthalpies Reading: Zumdahl 9.6 Outline –What is a standard enthalpy? –Defining standard states. –Using standard enthalpies to determine.

© 2006 Brooks/Cole - Thomson Some Thermodynamic Terms Notice that the energy change in moving from the top to the bottom is independent of pathway but.

 Enthalpy changes also occur when a compound is formed from elements.  Standard enthalpy of formation, ΔHº f, is the heat released or absorbed when one.

Energy Relationships in Chemical Reactions

Bomb Calorimetry constant volume often used for combustion reactions heat released by reaction is absorbed by calorimeter contents need heat capacity of.

Thermochemistry Chapter 5. First Law of Thermodynamics states that energy is conserved.Energy that is lost by a system must be gained by the surroundings.

Chapter 11 Thermochemistry Principles of Reactivity: Energy and Chemical Reactions.

Thermodynamics: Energy Relationships in Chemistry The Nature of Energy What is force: What is work: A push or pull exerted on an object An act or series.

Lesson 4 – Representing Enthalpy Changes. Method One THERMOCHEMICAL EQUATIONS WITH ENERGY TERMS THERMOCHEMICAL EQUATIONS WITH ENERGY TERMS a balanced.

Chapter 8 Thermochemistry. Thermodynamics  Study of the changes in energy and transfers of energy that accompany chemical and physical processes.  address.

Thermochem Quick review

Department of Chemistry and Biochemistry CHM Reeves The Nature of Energy The First Law of Thermodynamics Enthalpy Enthalpies of Reaction Calorimetry.

Inorganic chemistry Assistance Lecturer Amjad Ahmed Jumaa  Standard enthalpy of formation and reaction.  Calculating the standard enthalpy.

Thermochemistry Mrs. Stoops Chemistry.

1 Thermochemistry Chapter 7 CHEMISTRY - DMCU 1233 Fakulti Kejuruteraan Mekanikal, UTeM Lecturer: IMRAN SYAKIR BIN MOHAMAD MOHD HAIZAL BIN MOHD HUSIN NONA.

CHM 108 SUROVIEC SPRING 2014 Chapter 6 Energy Transfer.

Section 15.4 Calculating Enthalpy Change

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.

A Comparison of  H and  E 2Na (s) + 2H 2 O (l) 2NaOH (aq) + H 2 (g)  H = kJ/mol  E =  H - P  V At 25 0 C, 1 mole H 2 = 24.5 L at 1 atm P 

Hess’s Law SECTION 5.3. Hess’s Law  The enthalpy change of a physical or chemical process depends only on the initial and final conditions of the process.

Bond Enthalpies How does a chemical reaction have energy?

Thermochemistry Standard Enthalpies of Formation.

Standard Enthalpy of Formation Chapter 5.5 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Energy & Rates.

Bond Enthalpies 5.4.  Chemical reactions involve the breaking and making of bonds.  To understand the energy changes in a chemical reaction, we need.

Thermodynamics Review

Standard Enthalpy Changes of Reaction Section 15.1.

Thermochemistry Chapter 6. Thermochemistry is the study of heat change in chemical reactions.

Enthalpies of Formation. An enthalpy of formation,  H f, is defined as the enthalpy change for the reaction in which a compound is made from its constituent.

2 AlBr Cl 2 2 AlCl Br 2 Energy 2 AlBr Cl 2 2 AlCl Br 2  H rxn = Heat content of products – heat content reactants  H rxn < 0.

A simpler problem: How much heat is given off when 1.6 g of CH 4 are burned in an excess of oxygen if  H comb = -802 kJ/mol? Step 1: Write the reaction.

The basis for calculating enthalpies of reaction is known as Hess’s law: the overall enthalpy change in a reaction is equal to the sum of enthalpy changes.

Thermochem Hess’s Law and Enthalpy of Formation Sections 5.6 and 5.7.

Energy: Standard Enthalpy of Formation and Reaction – Direct & Hess’s Law Standard Enthalpy of Formation and Reaction.

Energy: Standard Enthalpy of Formation and Reaction – Direct & Hess’s Law Enthalpy Enthalpy (H): heat flow for a chemical reaction. q constant P.

Enthalpies of Formation and Reaction Definitions: Standard state –A gas at 1 atm –An aqueous solution with a concentration of 1 M at a pressure of 1 atm.

1 Hess suggested that the sum of the enthalpies (ΔH) of the steps of a reaction will equal the enthalpy of the overall reaction. Hess’s Law.

Hess’ Law. Many reactions can occur by many alternative routes. Hess' Law states: The enthalpy change for a reaction depends only on the energy of the.

 Certain reactions cannot be measured by calorimetry ◦ Ex: slow reactions, complex reactions, hazardous chemicals…  We can substitute in other reactions.

Thermochemistry. Thermodynamics  Study of the changes in energy and transfers of energy that accompany chemical and physical processes.  address 3 fundamental.

Chapter 51 Thermochemistry. 2 The Nature of Energy From Physics: Force – a kind of push or pull on an object. Energy – the capacity to do work. Work –

PRACTICE PROBLEMS Sample Problem Calculate the enthalpy change for the reaction in which hydrogen gas, H 2 (g), is combined with fluorine gas, F 2(g),

COURSE NAME: CHEMISTRY 101 COURSE CODE: Chapter 5 Thermochemistry.

THERMODYNAMICS REVIEW. ENERGY ABILITY TO DO WORK UNITS– JOULES (J), WE WILL USE “KJ” CAN BE CONVERTED TO DIFFERENT TYPES ENERGY CHANGE RESULTS FROM FORMING.

THERMODYNAMICS REVIEW. Energy Ability to do work Units– Joules (J), we will use “kJ” Can be converted to different types Energy change results from forming.

Gibbs Free Energy. Gibbs Free Energy (G) Balances the relationship between enthalpy (ΔH) and entropy (ΔS) Balances the relationship between enthalpy (ΔH)

Ch 5: Hess ’ s Law. Hess ’ s Law states.. “ the enthalpy change for a chem rxn is the same whether the rxn takes place in one step or several steps ”

Standard Enthalpy Changes of Reaction – Define and apply the terms standard state, standard enthalpy change of formation (ΔH f ˚) and standard.

Chapter 6 Thermochemistry: pp The Nature of Energy Energy – Capacity to do work or produce heat. – 1 st Law of Thermodynamics: Energy can.

The specific heat of gold is J/g  °C. How much heat would be needed to warm g of gold from 25°C to 100°C? Example 3:

Thermochemistry Chapter 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Acknowledgement Thanks to The McGraw-Hill.

Section 4: Calculating Enthalpy Change

Heat of Fusion (Hf) Q = mHf Fusion means melting/freezing

Warm-up (11/9) WS Day 3 out on desk, please

CHM 102 Sinex Enthalpy CHM 102 Sinex.

Hess’s Law and Standard Enthalpies of Formation

Enthalpy of formation - ΔHºf

Thermochemistry Part 2 – enthalpy.

Hess’s Law and Standard Enthalpies of Formation Unit 10 Lesson 4

Hess’s Law and Standard Enthalpies of Formation Unit 10 Lesson 4

Chemical Thermodynamics Lecture 1. Chemical Thermodynamics.

Chapter 5 Thermochemistry Part B

Either way, you get to the finish.

Hess’s Law and Standard Enthalpies of Formation

In Summary from Yesterday:

Presentation transcript:

State Function revisited….State Function revisited….  Dependent ONLY on a system’s state at a given moment in time.  Only initial and final states  Not based on the path to get to a given condition Ex. Energy, Enthalpy

Standard ConditionsStandard Conditions  Represented by a “ ° “ beside Δ H or Δ E, etc.  25°C  1 atm

Methods for determining Δ H 1)Calorimetry 2)Application of Hess’ Law

Hess’ LawHess’ Law  Enthalpy change for a chemical reaction is the same whether it occurs in multiple steps or one step  Δ H rxn = ΣΔ H A+B+C (sum of Δ H for each step)  Allows us to break a chemical reaction down into multiple steps to calculate Δ H  Add the enthalpies of the steps for the enthalpy for the overall chemical reaction

Guidelines for using Hess’ Law  Must use data and combine each step in a way that gives the chemical reaction with the unknown Δ H  Set up steps so chemical compounds not in the final reaction are cancelled  Reverse a reaction if necessary and change the sign on Δ H  Check for correct mole ratios

Example 1:Example 1: H 2 O (l)  H 2 O (g) Δ H° = ? Based on the following: H 2 + ½ O 2  H 2 O (l) Δ H° = kJ/mol H 2 + ½ O 2  H 2 O (g) Δ H° = kJ/mol

Example 2:Example 2: C (s) + 4H 2  C 3 H 8 (g) Δ H° = ? Based on the following: 2H 2 + O 2  2H 2 O Δ H° = kJ/mol C 3 H O 2  3CO 2 + 4H 2 O (g) Δ H°= kJ/mol C (s) + O 2  CO 2 (g) Δ H° = kJ/mol

Methods for determining Δ H 1)Calorimetry 2)Application of Hess’ Law 3)Enthalpies of Formation

Enthalpy of Formation ( Δ H f °)  Enthalpy for the reaction forming 1 mole of a chemical compound from its elements in a thermodynamically stable state.  Elements present in “most thermodynamically stable state”  25°C°, 1atm

Example 3Example 3  MgO (s) + CO 2 (g)  MgCO 3 (s) MgO + CO 2  Mg (s) + C (s) + 3/2 O 2 Mg (s) + C (s) + 3/2 O 2  MgCO 3

Apply Hess’ Law----Apply Hess’ Law----  Really Δ H f (products) - Δ H f (reactants)  Calculate Δ H rxn based on enthalpy of formation ( Δ H f )  aA + bB  cC + dD Δ H° =[c ( Δ H f °) C + d( Δ H f °) D ] - [a ( Δ H f °) A + b ( Δ H f °) B ]

Example 4Example 4  Calculate the Δ H° for the combustion of 1 mole of pentaborane (B 5 H 9) reacting with excess oxygen  2B 5 H O 2  5B 2 O 3 + 9H 2 O Δ H° = ?

Example 5Example 5  Isopropyl alcohol (rubbing alcohol) undergoes a combustion reaction 2(CH 3 ) 2 CHOH + 9O 2  6CO 2 + 8H 2 O Δ H° = kJ/mol Calculate the standard enthalpy of formation for isopropyl alcohol.

Homework  pp. 253 #65-67, 72