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					Energy, Chemistry, and
    Society-Part II
                  Experiment #8
              Moles NaHCO3 to NaCl




Source: Michele Young
             Experiment #10
    Comparison of the Energy Content of
                   Fuels

August 10, 12 – Experiment #10
August 17, 19 – Experiment #11 (Biodiesel)
August 17 – Term paper due
August 24, 26 – Energy content Biodiesel
                 Experiment #10
        Comparison of the Energy Content of
                       Fuels

1. Burn a fuel to heat water
2. Monitor temperature rise of known volume of water
3. 1 ml H2O = 1 g
4. Energy Content = fuel type + how much is burned

Example: CH4 + 2O2  CO2 + 2H2O + ∆ (heat)
CH3OH, C2H5OH, C3H7OH, C4H9OH,
C12H26 (lamp oil), C40H82 (candle wax)
                    Overview
  heat absorbed (calories) = m x ∆T x 1.00 cal/gC


1. Assemble the apparatus and obtain a burner containing a known fuel.
2. Add a measured volume of water to the soda can and then determine the mass of
   the water.
3. Weigh the burner.
4. Record the initial temperature of the water
5. Light the burner and heat the water until the temperature increases about 20C
6. Record the highest temperture of the water
7. Wight the burner again, in order to find the mass of fuel used.
8. Repeat with two or more additional fuel trials.
9. For each trial, calculate the amount of heat released per gram of fuel burned.
10. Calculate the calories of heat per 1 gram of fuel burned.
Kilimanjaro Summit
  Ice Depletion
                Melting Ice
 Where does the water go?
  – Oceans
  – By 2100 sea levels predicted to rise by 9-
    88 cm (3.5 – 34.6 in)
  – This endangers all costal cities – Seattle,
    San Francisco, Boston, Miami
  – Countries at sea level will be impacted:
      Indonesia, Bangladesh, the Philippines,
       the Netherlands
Impact of Rising
Temperatures on
   Northern
  Hemisphere
  Snow Packs
Gases Regulated by Kyoto Protocol
Carbon Sequestration-
  Capture/Storage
In the U.S., fossil fuel combustion provides
   • 70% of electricity
   • 85% of total energy

Fossil fuels produce large amounts of CO2

The supply of fossil fuels is finite, and may
 be running out (estimates vary)
  • 150 years left for coal
  • 50 years left for oil
      Energy Transformations

First Law of Thermodynamics:
Energy is neither created nor destroyed

Second Law of Thermodynamics
The entropy of the universe always
 increases during a spontaneous process
      Energy Transformations

First Law of Thermodynamics:
Energy is neither created nor destroyed
   – Conservation of Energy
   – Conservation of Mass
Energy can be converted from one form into
  another
         Energy Transformation
Second Law of Thermodynamics
  The entropy of the universe always increases
     during a spontaneous process
  It is impossible to completely convert heat into work
     without making some other changes in the universe
  Organized energy is always being transformed into
     chaotic motion or heat energy
Randomness is decreased only through a non-
 spontaneous process (work must be performed)
       Energy, work, and heat –
           some definitions

 Energy – the capacity to do work
 Work is done when movement occurs
  against a restraining force.
  – The force multiplied by the distance
 Heat is energy that flows from a hotter to a
  colder object.
  – Temperature is a measure of the heat content
    of an object.
      Energy, work, and heat

 Both work and heat are forms of molecular
  motion
  – Work is organized motion (all the
    molecules moving in the same direction)
  – Heat is random motion (all the molecules
    moving in different directions)
 Energy is the sum of all these molecular
  motions
                  Entropy
 The more disordered a sample, the higher
  the entropy
  – Boiled egg vs. scrambled egg
  – People sitting in a classroom vs. people
    walking in the halls
  – Gas vs. liquid vs. solid
  – Photosynthesis vs. combustion
  – Your desks vs. my desk
                   Entropy
 Another way of thinking about it… what is
  the probability of a particular state?
 Your text uses the example of a drawer full
  of socks
  – A drawer full of socks is more likely to be
    disordered than ordered
  – It is not impossible for a drawer full of socks
    to become organized…
  – … but it does require work for that to happen
    if you aren‟t willing to wait
       Energy, work, and heat
Units of Energy
  Joule
       The amount of energy required to raise a 1-
        kg book 10 cm against the force of gravity
       The amount of energy required for each
        beat of the human heart
  Calorie
       Defined as the amount of heat necessary to
        raise the temperature of exactly one gram
        of water by one degree Celsius
       1 cal = 4.184 J
       1 “food calorie” = 1 kcal = 1000 cal
        Energy Transformations

   Energy from fossil fuels
   Combustion
   Transform chemical energy to heat energy
   Engines transform heat energy into work
    energy
      Energy Transformation
Can we get complete energy conversion?
  Does all the potential energy get
   transformed into electricity (or even heat
   energy)



Efficiency measures the ability of an engine to
  transform chemical energy to mechanical
  energy
      Energy Transformation
Efficiencies are multiplicative
   Overall efficiency = efficiency of (power
     plant) x (boiler) x (turbine) x (electrical
     generator) x (power transmission) x (home
     electric heater)
How much energy does it take to heat
 your house for a month – say, January?
How much methane does the power plant
 need to burn in order to give your house
 that much electrical power?
Overall efficiency = efficiency of (power plant) x
(boiler) x (turbine) x (electrical generator) x
(power transmission) x (home electric heater)
Overall efficiency = .60 x .90 x .75 x .95 x .98
Overall efficiency = 0.34
34 % energy generated is used
The rest is wasted
         Energy Transformation

It takes about 3.5 x 107 kJ of energy to heat
   a house in January
Methane releases 50.1 kJ energy per gram
Efficiency of electric heat using natural gas: 34%
    Heat needed = heat used x efficiency
    Heat used = (heat needed) / efficiency
               = 3.5 x 107 kJ / .34 = 1.0 x 108 kJ
    Methane used = 1.0 x 108 kJ / 50.1 kJ = 2.0 x 106 g
         Energy Transformation
It takes about 3.5 x 107 kJ of energy to heat
   a house in January
Methane releases 50.1 kJ energy per gram
What if you didn‟t use the power plant‟s electricity, but
   just burned the methane yourself at home?
Efficiency of home heater using natural gas: 85%
    Heat needed = heat used x efficiency
    Heat used = (heat needed) / efficiency
                 = 3.5 x 107 kJ / .85 = 4.1 x 107 kJ
    Methane used =4.1 x 107 kJ / 50.1 kJ = 8.2 x 105 g
    Compared with 2.0 x 106 g methane to create
      electricity at the power plant
       Energy Transformation

 Potential Energy – energy stored in bonds,
  or intrinsic to position
 Kinetic Energy – the energy of motion
 Thermal Energy – random motion of
  molecules
 Entropy – randomness in position or energy
  level
  – Chaos
  – Disorder
         Formation of Water

 The overall energy change in breaking
  bonds and forming new ones is – 498 kJ
 The release of heat corresponds to a
  decrease in the energy of a chemical
  system
 This explains why the energy change is
  negative
             Formation of Water
         2 H2(g) + O2(g)  2 H2O(g) + energy
Reactants
  Hydrogen (2 molecules, each with 1 H-H bond)
  Oxygen (one O=O double bond)
Products
  Water (2 molecules, each with 2 H-O bonds)




Energy is released because there is energy left over
  872 kJ + 498 kJ – 1868 kJ = – 498 kJ (exothermic)
  Energy as a Barrier to Reaction
 Activation energy – the energy necessary
  to initiate a reaction
From Fuel Sources to Chemical Bonds

 Combustion of Propane, C3H8
  -2024 kJ/mol
 Combustion of Ethanol, C2H5OH
  -1281 kJ/mol
  Energy as a Barrier to Reaction
 Low activation energies – fast reaction
  rates
 High activation energies – slow reaction
  rates
 Useful fuels react at rates that are neither
  too fast nor too slow
 Smaller „bits‟ react faster than large „bits‟
 Increased temperatures help reactants to
  get over activation energy barrier
Laboratory Teams


2 students
 Per team
   Lab 8 – Baking Soda to Table Salt

 NaHCO3 + HCl  NaCl + H2O + CO2

 Quantitative measurement: moles NaCl
  from 1 mole NaHCO3
 Mole NaCl from Moles NaHCO3 is determined
  gravimetrically
 Overview of the Experiment

 – Label and weigh three test tubes
 – Add a weighed quantity of sodium
   bicarbonate to each test tube
 – React the sodium bicarbonate with 10% HCl
 – Evaporate the liquid remaining in the test
   tube after the reaction takes place (NaCl,
   must be DRY)
 – Determine the weight of sodium chloride
   produced
 – Calculate the ratio of moles of NaCl formed to
   moles of NaHCO3 used.
 Procedural Changes & Safety Notes

 – Safety goggles for everyone
 – 10% HCl – corrosive to skin/clothes
 – Use Bunsen burner in the hood to evaporate
   the water
 – Point the open test tube away from your
   partner and others
 – Use boiling chips in the tubes to prevent the
   solution from bumping during heating
 – Too rapid heating will cause splashing
      Combustion of Methane




 Total energy change in breaking bonds
   1664 kJ + 996 kJ = + 2660 kJ
 Total energy change in forming bonds
   - 1606 kJ + (-1868 kJ) = - 3474 kJ
 Net energy change
   2660 kJ + (-3474 kJ) = - 814 kJ
   From Fuel Sources to Chemical Bonds
This theoretical value (- 814 kJ) compares very
 favorably with the experimental value (- 802.3
 kJ). But it‟s not the same. Why not?
  • In real chemical reactions, not all the bonds
    are broken – just the pertinent ones
  • In real molecules, not all bonds the same
    type are energetically equal
      The O-H bond in water is not the same strength
       as the O-H bonds in hydrogen peroxide, H2O2
  • But we can calculate the energy of any
    reaction as if these assumptions were true,
    and get pretty close to the real answer
               Your Turn 4.8
 The heat of combustion of methane is 802.3
  kJ/mol. Methane is usually sold by the standard
  cubic foot (SCF). One SCF contains 1.25 mol of
  methane. What is the energy that is released by
  burning one SCF of methane.

             1.25 molCH 4    802.3 kJ
1 SCF CH 4                          1003 kJ
              1 SCF CH 4    1 molCH 4
From Fuel Sources to Chemical Bonds
 Combustion – combination of the fuel with oxygen
  to form products
   CH4(g) + 2 O2(g)  CO2(g) + 2 H2O(g) + energy
 Exothermic reaction – any chemical or physical
  change accompanied by the release of heat
 Heat of combustion – the quantity of heat energy
  given off when a specified amount the a substance
  burns in oxygen
   – Typically reported in kilojoules per mole
     (kJ/mol), but sometimes in kJ/g
   – Most* combustion reactions are exothermic
From Fuel Sources to Chemical Bonds
 CH4(g) + 2 O2(g)  CO2(g) + 2 H2O(g) + energy
 Heat of combustion of methane is -50.1 kJ/g
  – For every gram of methane burned we get 50.1 kJ
    energy
                  16.0 g CH 4   50.1 kJ
     1 mol CH 4                        802.3 kJ
                   1 mol CH 4 1 g CH 4
   – For every mole of methane burned we get 802.3 kJ
     energy
 The combustion of one mole of methane will always
  produce one mole of carbon dioxide, two moles of
  water, and 802.3 kilojoules of heat energy
   From Fuel Sources to Chemical
              Bonds




Energy change (DE) = Energyproducts – Energyreactants
      The SIGN of the change is important!
Energy Changes at the Molecular Level


 Bond energy – the amount of energy that
  must be absorbed to break a specific
  chemical bond.
 Can be used to estimate heats of reactions
Bomb Calorimeter
         Energy Consumption

 Pre-Historic man had only body and food for
  fuel
  – Used ~2000 kcal/day of energy
 Currently, Americans have access to a lot
  more technology
  – Use 650,000 kcal/day of energy
  – 65 barrels of oil or 16 tons of coal per person
    per year
History of US energy
consumption by source, 1800 -
2000




    History of US energy consumption by source, 1 EJ = 1018 J
Annual US energy consumption by source, 2002. „Other‟
includes wood, waste, alcohol, geothermal, wind and solar
      Properties needed in a fuel

   Contain substantial energy content
   Plentiful
   Burn readily at just the right rate
   Others…
Energy Content
                 Fossil Fuels
 “You will die but the carbon will not; its career
  does not end with you…it will return to the soil,
  and there a plant may take it up again in time,
  sending it once more on a cycle of plant and
  animal life”
   – Jacob Bronowski in Biography of an Atom – And the
     Universe.
Organic matter (plants, animals) decays upon
  death, producing CO2 and H2O, just like in
  combustion
But in some cases, decaying matter doesn‟t have
  enough O2 around to complete the reaction
Other reactions take place deep in the earth at
  high temperatures and pressures, producing
  coal, petroleum and natural gas.
          Fossil Fuels: Coal
 Was known in ancient times – used in
  funeral pyres as early as 3000 B.C.
 Mining for coal was not common until
  ~1300 A.D., in Britain
 During the Industrial Revolution (beginning
  in the 1700s), coal became the chief fuel
  source in Britain, and later the rest of the
  world
   – Fuel was needed in vast quantities to
     power the new Steam Engines
   – Wood was already in short supply
         Fossil Fuels: Coal
 Coal is a better energy source than wood
  – Coal yields 30 kJ per gram
  – Wood yields 12 kJ per gram

 Coal has higher ratio of carbon (85% by
  mass)
  – Fuels with a higher carbon ratio produce
    more energy when they are burned
  – An approximate molecular formula for
    coal is C135H96O9NS
 As carbon content increases, so does the heat
  content
 The less oxygen a compound contains, the more
  energy per gram it will release on combustion
 “Better” coals have been exposed to higher
  pressures for longer times, losing more oxygen
  and becoming harder
            Fossil Fuels: Coal
 Drawback #1: Difficult to obtain
  – Underground mining dangerous and
    expensive
  – Since 1900 more than 100,000 workers killed
    in American mine disasters – but how many
    worldwide? And how many have been made
    sick, or died from “black lung”?
 Drawback #2: Coal is a dirty fuel
  – Soot
  – Sulfur and nitrogen oxides
  – Mercury
  – Carbon dioxide
            Fossil Fuels: Coal
 The benefit of coal: the global supply is
  large
      20-40 times greater than petroleum

 Because of this, coal is expected to
  become a much more important fuel in the
  next 100-150 years

 It will become important to find ways to
  better use coal – more cleanly, more
  safely
    Calculations Concerning Coal
1. Compute the amount of energy released by
   burning 1.5 million tons of coal – the amount
   consumed at an average coal-burning plant in
   one year, assuming this coal produces 30 kJ per
   gram

2. How much C is in 1.5 million tons of
   C135H96O9NS?

3. How much CO2 would be produced from that
   combustion?
              C135H96O9NS
         C + O2  CO2 + Energy
   135 mol C x 12.0 g/mol = 1620 g C
   96 mol H x 1 g/mol = 96 g H
   9 mol O x 16 g/mol = 144 g O
   1 mol N x 14 g/mol = 14 g N
   1 mol S x 32 g/mol = 32.1 g S
   1 mol C135H96O9NS = 1906 g/mol
   1620 g C per 1906 g Coal
               C135H96O9NS
          C + O2  CO2 + Energy
 1620 g C per 1906 g Coal
 [1 g = 1.1023 x 10-6 short tons (long, metric)]
 mass-to-mass relationship stays the same,
  as long as same mass unit is used for both
 1620 tons C per 1906 tons Coal
 1.5 x 106 tons Coal (per year) x 1620 tons
  C/1906 tons Coal = 1.3 x 106 tons C
 44 tons CO2/12 tons C x 1.3 x 106 tons C =
  4.77 x 106 tons CO2
 (4.77 million tons per year-power plant)
      Fossil Fuels: Petroleum
 Liquid - easy to pump to surface
 Transported via pipelines
 Higher energy content than coal
   – 48 kJ/g for petroleum
   – 30 kJ/g for coal
 Petroleum (crude oil) easily converted to
  gasoline
 Around 1950, oil surpassed coal as the primary
  fuel in the U.S.
 In 1998, the U.S. burned 125 billion gallons in
  more than 203 million vehicles
 The U.S. consumes 25% world‟s oil … for 5% of
  the population
U.S. petroleum product use, domestic production, and
imports. In 2002, more than 50% of total oil used in U.S.
is imported.
Sources of crude oil and petroleum products
imported by US (August 2003)
2010 U.S. Energy Information Administration
May 11, 2010
World Energy Consumption by Region
CO2 Emissions by Region 1990-2030
Mongabay.com
Rainforest News
Environmental News
http://www.mongabay.com

Summer from hell: seventeen nations hit all-time heat records
Jeremy Hance
mongabay.com
August 09, 2010

          1. Belarus               2. Ukraine               3. Cyprus
          4. Russia                5. Finland               6. Qatar
          7. The Sudan             8. Saudi Arabia          9. Niger
          10. Chad                 11. Kuwait               12. Iraq
          13. Pakistan             14. Columbia             15. Myanmar
          16. Ascension Island     17. Solomon Islands
Mongabay.com
Rainforest News
Environmental News
http://www.mongabay.com



Hottest Temperature ever recorded in Asia:

                  Pakistan-Summer 2010

                          128F
 Mongabay.com
 Rainforest News
 Environmental News
 http://www.mongabay.com



Officials point to Russian drought and Asian
deluge as consistent with climate change

2010 the second hottest year on record through May

Freak floods in US predicted by 2009 climate change
report

NASA satellite image reveals record low snow for
the United States
Mongabay.com
Rainforest News
Environmental News
http://www.mongabay.com




                          Monthly average
                          carbon dioixde
                          concentration
                          measured at the
                          Mauna Loa
                          Observatory in
                          Hawaii 1958-2005
Rising Sea Levels
& Rising Global
Temperatures
       Fossil Fuels: Petroleum

 Crude oil must be refined
 Mostly hydrocarbons – molecules consisting
  of hydrogen and carbon atoms
   – Range from 1 to 60 carbon atoms per
     molecule
 Mostly alkanes – hydrocarbons with only
  single bonds between carbons
Oil Refinery
       Distillation –
        purification, or
        separation, process in
        which a solution is
        heated to its boiling
        point and the vapors
        are condensed and
        collected
The higher the number of
carbons contained in the
molecule, the higher the
boiling point.


The most volatile
components of the
fractionating tower boil far
below room temperature
and are called refinery
gases.
                 Petroleum
 The gasoline fraction contains hydrocarbons with
  5 to 12 carbon atoms per molecule
 One barrel of crude oil contains 42 gallons
 35 gallons of this is used for heating and
  transportation
      Manipulating Molecules
 Gasoline that comes directly from the
  fractionating tower represents less than 50%
  of the original crude
 Heavier and lighter fractions can undergo
  chemical reactions to form more gasoline
      Manipulating Molecules
 Cracking - a chemical process by which
  large molecules are broken into smaller
  ones suitable to be used in gasoline
  – C16H34  C8H18 + C8H16
  – C16H34  C5H12 + C11H22
 Thermal cracking – heat crude oil to high
  temperature so it decomposes
 Catalytic cracking – lower temperature
  process using a catalyst
       Manipulating Molecules
 Catalytic combination – use a catalyst to join
  smaller molecules together to form
  intermediate sized ones
  4 C2H4  C8H16
       Manipulating Molecules
 Isomers –compounds
  with the same chemical
  formula but different
  chemical structures.
  – C8H18
  – Octane – boiling point
    125oC
  – Isooctane – boiling point
    99oC – ignites more
    readily.
    Internal Combustion Engine
http://auto.howstuffworks.com/engine1.htm
http://auto.howstuffworks.com/engine4.htm
                 Knocking
 Premature ignition during the compression
  stroke
 Noisy and can damage the engine
 Octane rating of gasoline
   The higher the number, the less likely the
     gas will cause knocking
 Octane can be reformed to isooctane
 Oxygenated fuels are octane boosters
 Newer Fuels and Other Sources
 Oxygenated gasolines –
  blends of petroleum-
  derived hydrocarbons with
  oxygen-containing
  compounds such as MTBE
  (methyl tertiary butyl ether)
  and ethanol.
 They reduce the carbon
  monoxide emissions, since
  fuel contains oxygen
  (ethanol)
Newer Fuels and Other Sources
 Winter Oxyfuel Program (1992)
  – Part of the Clean Air Act
  – Reduce CO emissions
  – During winter months, gasoline must contain
    2.7% oxygen by weight
  – Typically ethanol
Newer Fuels and Other Sources
 Year-round Reformulated Gasoline Program
  (1995)
  – Part of clean air act
  – Reformulated gasolines (RFGs) are oxygenated
    gasolines that also contain a lower percentage
    of certain more volatile hydrocarbons, such as
    benzene found in non-oxygenated conventional
    gasoline
      Reformulated gasolines
 <1% benzene
  – Benzene is a carcinogenic compound
 >2% oxygenates
  – Burn cleanly
 Evaporate less easily than conventional
  gasoline
  – Fewer smog-forming pollutants
 30% US gasolines are RFGs – with 90%
  containing MTBE
                        MTBE
 In January 2004, the National Institute of Environmental
  Health Sciences reported the human health effects of
  short-term exposure to large or small amounts of MTBE
  are not known.
 MTBE is very soluble in water and is finding its way to
  drinking water
 Little likelihood that MTBE will cause adverse health
  effects at concentrations of 40 ppb or below – above this
  concentration one can taste it in the water
 California has phased out the use of MTBE in gasoline,
  and many local governments in the Northeast have started
  the same process
 Because this represents a huge market, most gasoline
  providers have stopped using MTBE and have replaced it
  with other additives – particularly ethanol
Newer Fuels and Other Sources
 Coal supply bigger than petroleum supply
 Convert coal into gaseous and liquid fuels


   C  s   H 2O  g   CO  g   H 2  g 
    coke                        water gas


  CO  g   H 2  g   hydrocarbons
                        catalyst
                                 
       water gas
Newer Fuels and Other Sources
 Biomass
  – Materials produced by biological processes
  – Wood
  – Ethanol, CH3CH2OH
      Produced by fermentation of starch and
       sugars in grains such as corn
      Can also be prepared commercially by the
       reaction of water with ethylene (C2H4)
  – Biodiesel
Newer Fuels and Other Sources
                  Gasohol
                   – Mix 10% ethanol
                     with 90% gasoline
                   – Can be burned in a
                     standard car engine
                  Ethanol produces
                   29.7 kJ/g of energy
                  Octane produces
                   47.8 kJ/g of energy
Newer Fuels and
 Other Sources
 Flexible Fuel Vehicles
   – Detect what the fuel
     actually is, and adjust
     engine performance to
     match
   – Can use E85 – 85%
     ethanol and 15% gasoline
   – It is believed that most
     FFV owners (4 million as
     of 2006) are not aware
     that their vehicles can run
     on E85: fewer than 1% of
     the consumed fuel is E85
  Drawbacks of Ethanol as Fuel
 Not as much energy (gram per gram) as gasoline
 How much farmland would need to be diverted
  from food production to get ample fuel
  production?
 How much is needed? Estimates are that
  California alone will consume 20% of the ethanol
  produced in the U.S.
 Expense ($$ and Energy)
  –   Energy required to plant, cultivate and harvest corn
  –   Production and application of fertilizers
  –   Distillation of alcohol
  –   Tractors used in farming
  –   More energy to produce a gallon of ethanol than
      obtained from burning?
Biodiesel
      Can be used in any
       standard diesel engine
      Natural and renewable
       resources
        – New and used
          vegetable oils and
          animal fats
      Burn more cleanly and
       more efficiently than
       traditional diesel
               Garbage Power
 140 U.S. power plants use garbage as fuel source
  – Hennepin Energy Resource Company in Minneapolis
    converts 365,000 tons of garbage per year into enough
    energy to provide power to 25,000 homes
  – One truckload of solid waste generates the same
    amount of energy as 21 barrels of oil
  – They‟ve since built a second facility that processes
    another 235,000 tons
 Simultaneously addresses two major problems:
  Energy and Waste
 Downside? Incineration process is efficient but
  produces CO2
             Garbage Power
 Methane Generators
  – Animal and vegetable wastes are fermented
    to form “biogas”
      60% methane
      Can be used for cooking, heating, lighting,
       refrigeration, electrical generation
      The manure from 2 cows provides enough
       energy to support a farm family
  – Prevalent in China and India. In China, 2/3 of
    rural families use biogas as their primary fuel

				
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