Chem II: 10/15
Objectives:
• Complete Midterm Make-up problems
•Assess Redox Titration Lab
•Review Thermochemistry Concepts
Homework:
•Thermochemistry Worksheet
Redox Titration Lab
http://www.webassign.net
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 change
b. Exothermic change
c. Ice cream melting
d. Dew condensing on grass
e. Combustion of fossil fuels: CH4 + 2O2 ---> 2H2O + CO2
f. Photosynthesis
Primary Phase Changes
Energy Diagrams
Sublimation
en.wikipedia.org
chemistryjournal104dianegan8.blogspot.com
Deposition
www2.volstate.edu
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 change
b. Exothermic change
c. Ice cream melting
d. Dew condensing on grass
e. 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: Thermometer
•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
Thermometers
Visionlearning.com
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: 10/17
Due:
•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: Thermochemistry
1. What is thermochemistry?
2. Determine if the following changes represent an
endothermic or exothermic proccess.
a. making popsicles
b. evaporating water
c. sublimation of carbon dioxide
d. 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 Substances
Substances
Specific Heat
J/g* 0C
Specific Heat
cal/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: 10/18
Infinite Campus Update:
•Chemistry Midterm Make-ups
•Hydrogen Peroxide Titration Lab Corrections
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: Post Lab Questions
Thermochemistry Applications
Thermochemistry Quiz
1.
2.
3.
a.
b.
c.
What is the 1st Law of Thermodynamics
What is calorimetry?
Classify each as either endothermic or exothermic.
CaO (s) + H2O (l) ----> Ca(OH)2 (s) + 65.2 kJ
water condensing
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: 10/21
Infinite Campus Update:
•Chemistry Midterm Make-ups
•Hydrogen Peroxide Titration Lab Corrections
Objectives:
•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 J
7. 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 = 6,000J
10. a. C = 0.20J/gK
b. Q = 24J
Chem II: 10/22
Infinite Campus Update:
•Thermochemistry Quiz
Due:
Calorimetry Food Lab Report
Objectives:
•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
www.physicslessons.com
Calorimetry
• Measurement of
heat flow in and out
of a system during
physical/chemical
changes.
• Energy equation and
1st Law of Thermodynamics
is 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 Problems
When 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: 10/24
Infinite 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 Equation
CaO (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: 10/25
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.
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 Reaction
1. 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
http://webmail.warwickschools.org
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: 10/28
Objectives:
•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 multistep 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: 10/29
Due:
•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 cal
In addition: 67., 69., 72., 73., 74., 82
Chem II: 10/30
Due:
•Thermochemistry Textbook Problems
Objectives:
•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 kJ
NaOH(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: 10/31
Infinite 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 kJ
NaOH(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
1
2
3
4
5
6
7
8
T
Heats of Reaction: Hess’s Law
Post Lab Questions:
• Omit question 6
Chem II: 11/4
Due:
•Heats of Reaction Lab
Objectives:
•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 nonspontaneous.
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 Equation
Purpose:
• 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 Equation
Purpose:
• 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 Reactions
What 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 nonspontaneous reactions.
Entropy
What 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: 11/5
Due:
•Heats of Reaction Lab
Objectives:
•Peer Review of Lab Reports
•I can calculate and perform dilutions in the lab.
•I can classify reactions as spontaneous or nonspontaneous.
Homework:
Gibbs Free Energy Calculations
Make changes to Heats of Reaction Lab (due Wed.)
Dilution Equation
Purpose:
• 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: 11/6
Due:
•Heats of Reaction Lab Modified
Objectives:
•I can classify reactions as spontaneous or nonspontaneous.
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
decreases (exothermic) increases
increases
(endothermic)
increases
decreases
(exothermic)
decreases
increases
(endothermic)
decreases
Spontaneous Reaction?
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 25C
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: 11/7
Due:
Gibbs Free Energy Calculations
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.
•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 Slip
1. 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 water
b. 25mL of water or 25 ml of water vapor
c. synthesis of water or decomposition of water
4. 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.
•Radiation evenly distributed throughout the universe.
•Temp: -270 oC (few degrees above absolute zero)
•Minute fluctuations in temperature observed.
bbc.co.uk
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.
dailygalaxy.com
Metallic Bonding
Intermolecular Forces
itl.chem.ufl.edu