Chem II: 10/15

Objectives:• Complete Midterm Make-up problems•Assess Redox Titration Lab•Review Thermochemistry Concepts

Homework:•Thermochemistry Worksheet

Redox Titration Lab

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Redox Titration Lab

5H2O2 + 2KMnO4 +3H2(SO4) 2Mn(SO4) +K2(SO4) + 5 O2+ 8H2O

Chem II: 10/15

Due:•Corrections to Titration Lab

Objectives:•Review Thermochemistry Concepts

Homework:•Calorimetry Lab: Read and complete pre-lab qts.

Thermochemistry

1. What is thermochemistry?2. Determine which energy diagram is associated

with each example below: a. Endothermic changeb. Exothermic changec. Ice cream meltingd. Dew condensing on grasse. Combustion of fossil fuels: CH4 + 2O2 ---> 2H2O + CO2

f. Photosynthesis

Primary Phase Changes

Energy Diagrams

Sublimation

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Deposition

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Thermochemistry

• Study of energy changes between matter during a physical or chemical change.

• Energy changes can be measured two ways:- the ability to do work on an object- the transfer of heat between objects

• What are the two types of energy?-Potential Energy= stored energy, energy in chemical bonds-Kinetic Energy = energy of motion, particle movement

Heat Energy

Heat Energy: • Energy that is transferred between matter of

different temperatures. • Heat energy is also called kinetic energy. • Units for Energy: Joules (J) or calories (cal)• Energy does not have mass or volume, therefore it

is NOT classified as matter.

• How does heat energy flow between objects of different temperatures?

-Always from hot to cold

Heat Energy Flow

Energy flows between: • The System: The matter you are studying/measuring.• The Surrounding : The matter (environment) around the system.

Energy Processes:• Endothermic Process: When more heat is absorbed by the system.• Exothermic Process: When more heat is released by the system.

Energy Diagrams

Thermochemistry: Chpt. 10

1. What is thermochemistry?2. Determine which energy diagram is associated

with each example below: a. Endothermic changeb. Exothermic changec. Ice cream meltingd. Dew condensing on grasse. Combustion of fossil fuels: CH4 + O2 ---> H2O + CO2

f. Photosynthesis

Conservation of Matter and Energy

Matter:• Matter undergoes changes, but the atoms are conserved.

Energy:• Energy is also conserved during

changes.• If energy increases for a system,

then its surroundings must decrease in energy by the same amount.

• 1st Law of Thermodynamics

• Energy changes between the system and its surroundings can be measured using a thermometer.

• (Energy changes = Temperature changes)

• Temp. change indicates a change in speed of particles of system or surroundings.

• Primary unit of measurement by scientists: Celsius (oC) and Kelvin (K) scales

Energy Changes: Thermometer

Thermometers

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K = oC + 273

Thermochemistry

The amount of energy transferred between matter depends upon the ..?

- chemical make-up of the matter- the mass of the matter- temperature difference between the matter

Chem II: 10/17Due:•Corrections to Titration Lab (last day)•Midterm Make-up (last day)Objectives:•I can distinguish between endothermic and exothermic processes during changes with matter.•I can calculate and analyze energy calculations during changes with matter. Homework:•Calorimetry Lab: Bring junk food/aluminum can (12oz.)

Bell Ringer: Thermochemistry1. What is thermochemistry?2. Determine if the following changes represent an

endothermic or exothermic proccess.a. making popsiclesb. evaporating waterc. sublimation of carbon dioxided. Sb + I2 + energy --------> SbI3

e. PCl3 + Cl2 ----------> PCl5 + energy

3. What is the 1st Law of Thermodynamics?4. Is calorie, a unit of energy, the same calorie found in food?5. What is specific heat capacity?

Energy Diagrams

Conservation of Matter and Energy

Matter:• Matter undergoes changes, but the atoms are conserved.

Energy:• Energy is also conserved during

changes.• If energy increases for a system,

then its surroundings must decrease in energy by the same amount.

• 1st Law of Thermodynamics

Heat Energy

Heat Energy: • Energy that is transferred between matter of

different temperatures. • Heat energy is also called kinetic energy. • Units for Energy: Joules (J) or calories (cal)• Energy does not have mass or volume, therefore it

is NOT classified as matter.

• How does heat energy flow between objects of different temperatures?

-Always from hot to cold

Specific Heat Capacity

Specific Heat Capacity (c ):The amount of heat needed to raise the temperature of a one

gram sample one Celsius degree (oC) or one Kelvin (K).

Specific Heats of Common SubstancesSubstances Specific Heat

J/g* 0CSpecific Heatcal/g*oC

water 4.18 1.00

Grain alcohol 2.4 0.58

ice 2.1 0.50

steam 1.7 .40

aluminum 0.90 0.21

silver 0.24 0.057

mercury 0.14 0.033

Specific Heat Calculations

• The temperature of a 95.4 gram piece of copper increases from 25.0oC to 48.0oC when the copper absorbs 849 Joules of heat. What is the specific heat of copper? (we’ll go over in class)

Chem II: 10/18Infinite Campus Update:•Chemistry Midterm Make-ups•Hydrogen Peroxide Titration Lab CorrectionsObjectives:•I can distinguish between endothermic and exothermic processes during changes with matter.•I can calculate and analyze energy calculations during changes with matter. Homework:•Calorimetry Lab: Post Lab Questions

Thermochemistry Applications

Thermochemistry Quiz1. What is the 1st Law of Thermodynamics2. What is calorimetry?3. Classify each as either endothermic or exothermic. a. CaO (s) + H2O (l) ----> Ca(OH)2 (s) + 65.2 kJ

b. water condensingc. Which of the following energy diagrams represent the

following change:

4. What is specific heat capacity of matter?

Calorimetry Food Lab Purpose:To indirectly determine the Calorie content in specific

snack foods.

Pre-Lab: • Read background and complete pre-lab questions.

Chem II: 10/21Infinite Campus Update:•Chemistry Midterm Make-ups•Hydrogen Peroxide Titration Lab CorrectionsObjectives:•I can distinguish between endothermic and exothermic processes during changes with matter.•I can calculate and analyze energy calculations during changes with matter. (Calorimetry Food Lab)

Thermochemistry Worksheet-Key

6. Q = 6,300 J7. Q = -15,000 J= -20,000 J (sig. figs.)8. a. Q water = 336,000 J = 300,000 J

b. Q Cu saucepan = 9,600 J = 10,000 J

9. Q = 5,850J = 6,000J10. a. C = 0.20J/gK b. Q = 24J

Chem II: 10/22Infinite Campus Update:•Thermochemistry QuizDue: Calorimetry Food Lab ReportObjectives:•I can distinguish between endothermic and exothermic processes during changes with matter.•I can analyze energy changes during chemical and physical processes.

Calorimetry Food Lab

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Calorimetry

• Measurement ofheat flow in and outof a system duringphysical/chemical changes.

• Energy equation and 1st Law of Thermodynamicsis used to calculate energy transferrred by system.

www.physicslessons.com

Enthalpy• The amount of energy contained by a system at constant

pressure. (usually room temperature, 1atm)

• H= The change in energy of a system during a reaction occuring at constant pressure.

• Heat released or absorbed by system , Q

• Q = H, at constant pressure

•

Calorimetry: Enthalpy Changes

Enthalpy Calorimetry ProblemsWhen 25 mL of water containing 0.025 mol HCl at 25oC is

added to 25.0 mL of water containing 0.025 mol of Na(OH) at 25oC in a foam calorimeter, a reaction occurs. Calculate the enthalpy change in kJ during this reaction if the highest temperature observed is 32oC. Assume the densities of the solutions are 1.00g/mL and the specific heat of water is 4.184 J/goC.

Chem II: 10/24Infinite Campus Update:•Thermochemistry Quiz•Calorimetry Lab (29pts.)Objectives:•I can distinguish between endothermic and exothermic processes during changes with matter.•I can analyze and calculate energy changes during chemical and physical processes.

Thermochemical Equations

• A chemical equation that includes the enthalpy change.

1. CaO (s) + H2O(l) -----> Ca(OH)2 (s) + 65.2 kJ

CaO (s) + H2O(l) -----> Ca(OH)2 (s) H = -65.2 kJ

2. 2Na(HCO3)(s) + 129kJ -----> Na2(CO3) (s) + H2O (l) + CO2 (g)

2Na(HCO3) (s) -----> Na2(CO3) (s) + H2O (l) + CO2 (g)

H= 129 kJ H = heat of reaction

Thermochemical EquationCaO (s) + H2O(l) -----> Ca(OH)2 (s) H = -65.2 kJ

Heat of Reaction: ( H )• The enthalpy change for a chemical reaction based

on the balanced equation at standard conditions.• Standard temperature , 25oC (room temp.)• Standard pressure, 1atm.• Reactants/products states of matter must be at

room temperature. • Enthalpy change depends upon moles of

substances in the reaction.

Heat or Reaction Calculations

Using the thermochemical equation below, calculate the amount of heat in kJ required to decompose 2.24 mol Na(HCO3).

• 2Na(HCO3) (s) -----> Na2(CO3) (s) + H2O (l) + CO2 (g)

H= 129 kJ

Heats of Reaction Calculation

Heat of Combustion• Heat of reaction for the complete burning of one

mole of fuel. CH4 (g) + 2O2 (g) -----> H2O(l) + CO2 (g) H = -890kJ

Substance Chemical Formula Enthalpy Change (kJ/mol)

Hydrogen H2 -286

Carbon C (s) graphite -394

Methane CH4 (g) -890

Ethanol C2H5OH -1,368

Enthalpy: Changes in State

• Molar heat of fusion

• Molar heat of solidification

• Molar heat of vaporization

• Molar heat of condensation

Enthalpy: Changes in State• Molar heat of fusion: H(fus)

Amount of heat absorbed by one mole of solid as it melts to a liquid at constant temperature.

• Molar heat of solidification: H(solid)

Amount of heat released by one mole of liquid as it freezes to a solid at constant temperature.

• Molar heat of vaporization: H(vap)

Amount of heat absorbed by one mole of liquid as it vaporizes to a gas at constant temperature.

• Molar heat of condensation: H(cond)

Amount of released by one mole of gas as it condenses to a liquid at constant temperature.

Chem II: 10/25Objectives:•I can distinguish between endothermic and exothermic processes during changes with matter.

•I can analyze and calculate energy changes during chemical and physical processes.

Homework: Textbook Problems

Energy Calculations: Homework

Homework Problems: (pg. 535-536)*43., 46., 47., 55., 56., 58., 59., 62., 66., 69.*Energy conversions: 1,000cal = 1Cal 1 J = 0.2390 cal

Bell Ringer: Heats of Reaction1. Identify each type of enthalpy change by name and

classify each as exothermic or endothermic. a. 1 mol of H2O (l) ----> H2O (g)

b.1 mol of NaCl (aq) ----> 1 mol NaCl (s)

2. Complete Heat Curve Graph

Heat Curve Graph

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Enthalpy: Heat of Solution Molar Heat of Solution: H(soln.)

• Heat is either absorbed or released during the formation of a solution.

• The enthalpy change caused by the dissolution of one mole substance.

• Ex. Na(OH) (s) -----> Na+(aq) + OH-

(aq) H(soln.) = -445.1kJ/mol

Homework Questions

Calculating Heats of Reaction (pg. 527)

1. Why would scientists need to calculate the heats of reaction, H, when they can measure it by performing the reaction in the lab?

2. What are two ways scientists can calculate heats of reaction without performing the reaction in the lab.

Chem II: 10/28Objectives:•I can analyze and calculate energy changes during chemical and physical processes.

Homework:•Enthalpy Calculation Problems•Enthalpy Calculation Quiz Tuesday•Thermochemistry Test: Thursday

Calculating Heats of Reaction (pg. 527)

1. Why would scientists need to calculate the heats of reaction, H, when they can measure it by performing the reaction in the lab?

• Reaction might occur too slowly to measure.• Reaction might be an intermediate step is a multi-

step reaction.• Might want to preserve reactants in a reaction. • Reaction in lab might yield side products

(unwanted products) that affects the H.

Heat of Reaction Calculations• Enthalpy difference between reactants and

products is independent of pathway.

• Enthalpy change can be calculated two ways:* Hess’s Law: Sum of several thermochemical

equations.*Standard Heat of Formation: The difference in heat

of formation of products and reactants in the reaction.

H = Hf (products) - Hf (reactants)

Hess’s Law: Sum of Reactions CH4(g) + 2O2 (g) ----> 2CO2 (g) + 2H2O(l) H =?

C(s) + 2H2 (g) -----> CH4(g) H = -74.80 kJ/mol

C(s) + O2 (g) -----> CO2 (g) H = -393.50 kJ/mol

H2 (g) + 1/2O2 (g)----> H2O (l) H= -285.83 kJ/mol

Standard Heat’s of Formation CH4(g) + 2O2 (g) ----> 2CO2 (g) + 2H2O(l) H =?• Can calculate using standard heats of formation if

occurs at standard conditions. H = Hf (products) - Hf (reactants)• Standard Heats of Formation table (pg. 530)CH4(g) H =

O2 (g) H =

CO2(g) H =

H2O(l) H =

Chem II: 10/29Due: •Thermohemistry Textbook Problems

Objectives:•I can analyze and calculate energy changes during chemical and physical processes.•Heats of Reaction Quiz

Homework:Read Hess’s Law lab and complete background qts.

Gallery Walk Practice Problems

• Apply Hess’s Law and Standard Heats of Formation in calculating heats of reaction.

Energy Calculations: Homework

Homework Problems: (pg. 535-536)*43., 46., 47., 55., 56., 58., 59., 66., 69.*Energy conversions: 1,000cal = 1Cal 1 J = 0.2390 calIn addition: 67., 69., 72., 73., 74., 82

Chem II: 10/30Due: •Thermochemistry Textbook ProblemsObjectives:•I can analyze and calculate energy changes during chemical and physical processes.•Complete Heats of Reaction Quiz•Hess’s Law Lab

Homework:Complete Post-Lab Qts.

Heats of Reaction Quiz

2NO2 ----> N2O4 (g) = H = ?

• 2N2(g) + 2O2(g) ----> 2NO2 (g) H = 67.7 kJ

• N2(g) + 2O2 (g) ---> N2O4 (g) H = 9.7kJ

Hess’s Law Lab

Heats of Reaction Lab: Hess’s Law

Na(OH)(s) + HCl (aq) ----> NaCl(aq) + H2O (l) H=?NaOH (s) ----> NaOH (aq) H =- 44 kJNaOH(s) + HCl (aq) ----> NaCl (aq) + H2O(l) H = -55.6 kJ

Pre-Lab Questions:1. Use Hess’s Law to calculate the theoretical H for our

desired reaction. 2. As you perform each of these reactions in the lab, do you

predict the temperature to increase or decrease? Explain your answers using the H values for each reaction.

3. Why is it important that the thermometer is NOT touching the sides of the cup as each reaction performed?

Chem II: 10/31Infinite Campus Update:•Heats of Reaction Quiz 25pts. Objectives:•I can analyze and calculate energy changes during chemical and physical processes.•Modify, complete, and analyze Heats of Reaction Lab.•Address Heats of Reaction Quiz Homework:Complete Post-Lab Qts and work on dilution problems.

Heats of Reaction Lab: Hess’s Law

Na(OH)(s) + HCl (aq) ----> NaCl(aq) + H2O (l) H=?NaOH (s) ----> NaOH (aq) H =- 44 kJNaOH(aq) + HCl (aq) ----> NaCl (aq) + H2O(l) H = -55.6 kJ

Pre-Lab Questions:1. Use Hess’s Law to calculate the theoretical H for our

desired reaction. 2. As you perform each of these reactions in the lab, do you

predict the temperature to increase or decrease? Explain your answers using the H values for each reaction.

3. Why is it important that the thermometer is NOT touching the sides of the cup as each reaction performed?

Heats of Reaction Lab: Hess’s Law Lab Group T

1

2

3

4

5

6

7

8

Heats of Reaction: Hess’s Law

Post Lab Questions: • Omit question 6

Chem II: 11/4Due:•Heats of Reaction LabObjectives:•I can analyze and calculate energy changes during chemical and physical processes.•I can calculate and perform dilutions in the lab. •I can classify reactions as spontaneous or non-spontaneous. Homework:Complete Molarity and Spontaneous Reaction Wksht.

Heats of Reaction Lab Report

• Title• Purpose• Materials: List of chemicals only• Hypothesis: Incorporate pre-lab qts.• Data: Qualitative (sentence) and quantitative (table)• Analysis: Incorporate post-lab qts.• Conclusion: Re-state purpose and results.

Dilution EquationPurpose: • Important when making different concentrated solutions

in the lab. • M1V1 = M2V2

Example: The lab calls for 800mL of 1M HCl solution. I have 12M HCl stock solution on the shelf.

a. How much stock solution do I need?

b. How much water is needed to dilute the stock solution to 1M HCl?

Dilution EquationPurpose: • Important when making different concentrated solutions

in the lab.

• M1V1 = M2V2

Dilution Equation

Ex.2: How many milliliters of aqueous 2M MgSO4 solution must be diluted with water to prepare 100mL of aqeous 0.4M MgSO4?

T or F: Does diluting a solution decrease the moles of solute in the solution? Explain your answer.

Spontaneous ReactionsWhat are spontaneous reactions?

http://en.wikipedia.org/wiki/Fireworks

Spontaneous Reactions • Release of free energy. • Increase in entropy of a system. • Favors production of products.Ex. H2(CO3) -------> CO2(g) + H2O(l)• Dependent upon temperature and pressure of

reaction. Ex. photosynthesis • Not associated with speed of reaction.

Free Energy• Gibbs free energy, G• Energy produced from exothermic reactions.• Energy that can be used to do work.• Many times the production of free energy is

used to initiate non-spontaneous reactions. (coupled reactions) Ex. Cells use free energy from spontaneous

reaction to produce proteins from non-spontaneous reactions.

EntropyWhat is entropy?How is does it increase the spontaneity of a reaction?

Entropy• The disorder of a system.• Law of Disorder: Tendency of a system to

move in a direction that favors disorder.• Achieve lowest possible energy for a system.

Chem II: 11/5Due:•Heats of Reaction LabObjectives:•Peer Review of Lab Reports •I can calculate and perform dilutions in the lab. •I can classify reactions as spontaneous or non-spontaneous. Homework:Gibbs Free Energy Calculations Make changes to Heats of Reaction Lab (due Wed.)

Dilution EquationPurpose: • Important when making different concentrated solutions

in the lab.

• M1V1 = M2V2

Heats of Reaction Lab Report: Peer Review• Title• Purpose• Materials: List of chemicals only• Hypothesis: Incorporate pre-lab qts.• Data: Qualitative (sentence) and quantitative (table)• Analysis: Incorporate post-lab qts.• Conclusion: Re-state purpose and results. 1.Check to ensure each section above is included in their

report. 2. Identify changes or additions you think needs to be made.3. Include a positive comment about their lab report.

4. Sign your name.

Heats of Reaction Lab Report: Peer Review• Title• Purpose• Materials: List of chemicals only• Hypothesis: Incorporate pre-lab qts.• Data: Qualitative (sentence) and quantitative (table)• Analysis: Incorporate post-lab qts.• Conclusion: Re-state purpose and results. 1.Check to ensure each section above is included in their

report. 2. Identify changes or additions you think needs to be made.3. Include a positive comment about their lab report.

4. Sign your name.

Entropy Changes • Read pg. 570 and write down examples of where entropy

increases for a system. • Applications or illustrations of increase in entropy.

Entropy Changes: S

Applications of increase in entropy: + S• Changes in state from solid---> gas.• Making solutions and dilutions. • In chemical reactions # of products > # of reactants• Temperature increases

Energy Change Worksheet

Chem II: 11/6Due:•Heats of Reaction Lab Modified

Objectives:•I can classify reactions as spontaneous or non-spontaneous.

Homework:Gibbs Free Energy Calculations Review over Thermochemistry content (Exam Fri.)

Spontaneous vs. Non-Spontaneous Reactions Factors that favor a spontaneous reaction: 1. System releases energy (production of energy)2. System increases in entropy. (disorder of system)

Enthalpy Change of System

Entropy Change of System

Spontaneous Reaction?

decreases (exothermic) increases

increases(endothermic)

increases

decreases(exothermic)

decreases

increases (endothermic)

decreases

Spontaneous Reactions : Predicting

• Given the following information predict if the following reaction is spontaneous or not. ,

SnCl4(l) + 2 H2O(l) SnO2(s) + 4 HCl(g)

H = 133.0 kJ and S = 401.5 J/K

Gibbs Free Energy Equation• Used to determine if a reaction is spontaneous.• Relationship between enthalpy, entropy, and temperature

of system.• G is free energy or energy used for work. • G = H – T S

Where: G = Gibbs free energy (energy for work) H = enthalpy change (total energy) S = entropy change (measure of disorder)If: G is negative the reaction is _____________.

If: G is positive the reaction is ______________.

Spontaneous Reactions: Gibbs Free Energy Equation

• Calculate G for the reaction below at 25C to determine if the reaction is spontaneous.

SnCl4(l) + 2 H2O(l) SnO2(s) + 4 HCl(g)

H = 133.0 kJ and S = 401.5 J/K

Chem II: 11/7Due:Gibbs Free Energy CalculationsObjectives:•I can distinguish between endothermic and exothermic processes during changes with matter.•I can analyze and calculate energy changes during chemical and physical processes.•I can calculate and perform dilutions in the lab. •I can classify reactions as spontaneous or non-spontaneous. •Review over Thermochemistry content Homework:Review over Thermochemistry content (Exam tomorrow)

Gibbs Free Energy Problems

• Room temperature= 25oC• Temp conversion: K = oC + 273.15

Thermometers

Visionlearning.com

K = oC + 273

Bell Ringer

Thermochemistry Review

Exit Slip1. How many mL of 2M MgSO4 solution must be diluted with

water to prepare 100mL solution of 0.4M MgSO4?

2. T or F: Does diluting a solution decrease the moles of solute in the solution? Explain your answer.

3. Circle the examples below where entropy increases.a. sugar granules or sugar waterb. 25mL of water or 25 ml of water vaporc. synthesis of water or decomposition of water4. When graphite reacts with hydrogen at 300K, H is -74.8

kJ and S is -0.0809kJ/K. a. Compare H and S to predict if the reaction is

spontaneous. b. Use Gibbs Free Energy equation to validate if it is

spontaneous or not.

Cosmic Background Radiation• Radiation evenly distributed throughout the universe.• Temp: -270 oC (few degrees above absolute zero)• Minute fluctuations in temperature observed.

bbc.co.uk

Composition of the Universe

dailygalaxy.com

Composition of the Universe

dailygalaxy.com

Normal Matter: Influenced by gravity and does emit or reflect light. Dark Matter: Influenced by gravity, but does not emit or reflect light. Dark Energy: Seems to oppose gravity. Currently most mysterious to scientists.

Metallic Bonding

Intermolecular Forces

itl.chem.ufl.edu