Option C Energy Density, Specific Energy, Carbon Footprint and Ocean Acidification.
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The document discusses energy density, specific energy, CO2 emissions, and global warming. It provides definitions for energy density as the energy produced per unit volume and specific energy as the energy produced per unit mass. Renewable energy sources can be replenished faster than they are used, while non-renewables are used faster than they can be replaced. Strategies to reduce CO2 emissions include improving energy efficiency, reducing dependence on carbon fuels, and using renewable energy and carbon capture/storage technologies.
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Option C Energy Density, Specific Energy, Carbon Footprint and Ocean Acidification.
- 1. http://lawrencekok.blogspot.com Prepared by Lawrence Kok Option C Energy Density, Specific energy and CO2 global warming and ocean acidification.
- 2. Energy density = energy produced per unit vol consumedvolume releasedenergy densityEnergy . . . = consumedmass releasedenergy energySpecific . . . =%100 . . ×= inputtotal outputuseful Efficiency Specific energy = energy produced per unit mass Renewable ↓ Replenished at rate faster than it is used Energy Energy efficiency Non renewable ↓ Used faster than they can be replaced Renewable Non renewable solar hydro geothermal biomass wind nuclear coal gasoline gas Carbon footprint. Strategies to reduce CO2 emission Increase energy efficiency/conservation Reduce dependency on carbon based Alternate source of energy (renewable) Capture and storage from fossil fuel CO2 sequestration, reduce deforestration Total amt greenhouse gas produced during human activity Expressed in CO2 equivalent.
- 3. Find specific energy/energy density of hexane. (density hexane = 0.6548g cm-1 ) ∆H combustion hexane , ∆Hc = - 4163kJ mol-1 Formula C6H14 Mr = 86.2 g mol -1 86.2 g release - 4163 kJ 1 g release – 4163/86.2 = 48.3 kJ 3 6.131 6548.0 2.86 cm Density Mass Vol Vol Mass Density === = consumedmass releasedenergy energySpecific . . . = consumedvolume releasedenergy densityEnergy . . . = Energy density ↓ Specific Energy x Density 48.3 x 0.6548 = 31.6 kJcm-1 131.6 cm3 release - 4163 kJ 1 cm3 release – 4163/131.6 = 31.6 kJ cm-3 Power station generate power, 550 x 106 Js-1 . Overall efficiency of 36% for conversion of heat to electricity Find energy generated (output) in 1 year Find energy needed (input) for energy generation Find mass coal used, assuming coal has ∆H of graphite Total energy output 550 x 106 x 60 x60x 24 x 365 = 1.73 x 1016 J 1 year kJinputTotal inputtotal inputtotal outputuseful Efficiency 13 16 1082.4. %100 . 1073.1 %36 %100 . . ×= × × = ×= ∆H comb graphite, ∆Hc = - 394kJ mol-1 M carbon Mr = 12 g mol -1 394 kJ released by – 1 mol C 4.82 x 1013 kJ released by – 1.22 x 1011 mol C 1 mol C – 12 g 1.22 x 1011 mol C – 1.47 x 1012 g of C
- 4. % mass carbon in coal – Highest CO2 emission highest when combusted kJinputTotal inputtotal inputtotal outputuseful Efficiency 7 7 1071.4. %100 . 1000.4 %85 %100 . . ×= × × = ×= 4.00 x 107 kJ energy required to heat a home. Methane combustion for heat is 85% efficient ∆H comb methane, ∆Hc = - 891 kJ mol-1 Formula CH4 Mr = 16 g mol -1 0.0221 x 106 cm3 release - 891 kJ 1 cm3 release – 891/0.0221 x 106 = 40126 kJ cm-3 Find mass methane required. Find specific energy and energy density for CH4 ∆H comb CH4 ∆Hc = - 891 kJ mol-1 Mr CH4 Mr = 16 g mol -1 (density CH4 = 723 x 10-6 g cm-1 ) consumedmass releasedenergy energySpecific . . . = consumedvolume releasedenergy densityEnergy . . . = 16 g release - 891 kJ 1 g release – 891/16 = 55.5 kJ Energy density ↓ Specific Energy x Density 55.5 x 723 x 10-6 = 40126 kJcm-1 36 6 100221.0 10723 16 cmVol Density Mass Vol Vol Mass Density ×= × == = − Find % mass carbon in coal (CH), gasoline (C8H18), gas (CH4) Suggest why coal is a poor choice for fuel % mass carbon in coal (CH) %92%100 13 12 %100 . . =×= ×= masstotal carbonmass % mass carbon gasoline (C8H18) %84%100 114 96 %100 . . =×= ×= masstotal carbonmass % mass carbon methane (CH4) %75%100 16 12 %100 . . =×= ×= masstotal carbonmass
- 5. Coal burned to produce 500 x 103 kJ , has specific energy of 33 kJ g-1 Find mass coal burned, if efficiency is 38%. MF for coal is CH. Find mass CO2 produced kJinputTotal inputtotal inputtotal outputuseful Efficiency 6 3 1031.1. %100 . 10500 %38 %100 . . ×= × × = ×= 33 kJ released by – 1 g coal 1.31 x 106 kJ released by – 39900 g coal ↓ Mol coal – 39 900/14 = 3062 mol CH + 1.25O2 CO→ 2 + 0.5H2O 1 mol CH – 1 mol CO2 3062 mol CH – 3062 mol CO2 Mass CO2 – mol x RMM Mass CO2 – 3062 x 44 = 135000g CO2 Fuel Specific energy/kJ g-1 Carbon content by mass/% Coal 32 94 Oil 42 83 hydrogen 142 0 Find CO2 produced for each 1000kJ energy from each source Identify best and worse fuel used. 32 kJ released by – 1 g coal 1000 kJ released by – 31.3 g coal ↓ % C by mass = 0.94 x 31.3 = 29.4 g C C + O2 → CO2 1 mol C – 1 mol CO2 12 g C – 44g CO2 29.4 g C – (44 x 29.4)/12 = 108g CO2 42 kJ released by – 1 g oil 1000 kJ released by – 23.8 g oil ↓ % C by mass = 0.83 x 23.8 = 19.7 g C C + O2 → CO2 1 mol C – 1 mol CO2 12 g C – 44g CO2 19.7 g C – (44 x 19.7)/12 = 72g CO2 142 kJ released by – 1 g H2 1000 kJ released by – 7 g H2 ↓ % C by mass = 0 ZERO Emission CO2 Click here Carbon calculator
- 6. Energy density ↓ Specific Energy x Density Fuel Formula ∆H combustion/kJ/mol-1 Ethanol C2H5OH -1367 Coal C - 394 C2H5OH + 3O2 → 2CO2 + 3H2O 1 mol ethanol – 2 mol CO2 2.2 mol ethanol – 4.4 mol CO2 Which release more CO2 ? Ethanol fuel Mass CO2 – mol x RMM Mass CO2 – 4.4 x 44 = 193g CO2 Coal fuel C + O2 → CO2 1 mol C - 1 mol CO2 8.3 mol C – 8.3 mol CO2 Mass CO2 – mol x RMM Mass CO2 – 8.3 x 44 = 366 g CO2 Find specific energy/energy density of ethanol and pure coal. (density ethanol/coal = 0.789 gcm-1 / 2267kg m-3 ) Find carbon footprint in mass CO2 produced when 100g ethanol/coal burn consumedmass releasedenergy energySpecific . . . = 46 g release - 1367 kJ 1 g release – 1367/46 = 29.7 kJ Energy density ↓ Specific Energy x Density 29.7 x 0.789 = 23.4 kJcm-1 consumedmass releasedenergy energySpecific . . . = 12 g release - 394 kJ 1 g release – 394/12 = 32.8 kJ 32.8 x 2267 = 74.3 kJcm-1 Mass ethanol, 100g – 100/46 = 2.2 mol Mass coal, 100g – 100/12 = 8.3 mol
- 7. 1.33 x 106 kJ energy (output) required to heat a home. Find % mass carbon in two fuels Find carbon footprint in terms of mass CO2 produced Fuel Formula Specific energy/kJ g-1 Efficiency / % Coal CH 31 65 Oil C5H9O4 22 70 % mass of carbon in Coal (CH) %2.92%100 112 12 %. . . %. =× + = = carbon masstotal carbonmass carbon % mass of carbon in oil (C5H9O4) %45%100 )64()9()60( 125 %. . . %. =× ++ × = = carbon masstotal carbonmass carbon 31 kJ released by – 1 g coal 2.05 x 106 kJ released by – 66000 g coal ↓ % C by mass = 0.922 x 66000 = 60 800g C kJInput inputtotal input output Efficiency 6 6 1005.2 %100 . 1033.1 %65 %100 ×= × × = ×= C + O2 → CO2 1 mol C – 1 mol CO2 12 g C – 44g CO2 60 800 g C – (44 x 60 800)/12 = 223000 g CO2 kJInput inputtotal input output Efficiency 6 6 109.1 %100 . 1033.1 %70 %100 ×= × × = ×= 22 kJ released by – 1 g oil 1.9 x 106 kJ released by – 86 400 g oil ↓ % C by mass = 0.45 x 86 400 = 38 900g C C + O2 → CO2 1 mol C – 1 mol CO2 12 g C – 44g CO2 38 900 g C – (44 x 38 900)/12 = 142000 g CO2 Which release more CO2 ?
- 8. 10 000 kJ energy (output) required to heat a home. Find carbon footprint in terms of mass CO2 produced Fuel Formula ∆H combustion/kJ/mol-1 Ethanol C2H5OH -1367 Methylbenzene C7H8 -3910 1367 kJ released by – 1 mol ethanol 10 000 kJ released by – 7.31 mol ethanol C2H5OH + 3O2 → 2CO2 + 3H2O 1 mol ethanol – 2 mol CO2 7.31 mol ethanol – 14.6 mol CO2 Which release more CO2 ? Ethanol fuel Mass CO2 – mol x RMM Mass CO2 – 14.6 x 44 = 643 g CO2 Methylbenzene fuel 3910 kJ released by – 1 mol C7H8 10 000 kJ released by – 2.56 mol C7H8 C7H8 + 9O2 → 7CO2 + 4H2O 1 mol C7H8 - 7 mol CO2 2.56 mol C7H8 – 17.9 mol CO2 Mass CO2 – mol x RMM Mass CO2 – 17.9 x 44 = 789 g CO2
- 9. GHG allow short wavelength radiation to pass through but absorb longer wavelength, IR radiation from earth. Some radiation is re radiated back to earth Greenhouse Effect Re radiated long wavelength Re radiated long wavelength Greenhouse Gases (GHG) Gas Greenhouse factor/GWP Relative abundance/% Overall contribution Carbon dioxide CO2 1 0.036 50 Water (H2O) 0.1 0.1 - Methane(CH4) 30 0.0017 18 Dinitrogen oxide (N2O) 280 0.0003 6 Hydrofluorocarbon (HFC) 400-10000 - - CFC 11000 - - Perfluorocarbon (PFC) 9000 - - Sulphur hexafluoride (SF6) 16000 - - Global Warming Potential Global Warming Potential (GWP) Compare ability of gas to absorb IR radiation to CO2 absorbing ability (as a std) Water – main/abundant greenhouse gas – produced naturally – Contribution not significant
- 10. Molecule CO2 absorb IR • Vibration within molecule cause a net change in dipole moment • Freq of radiation matches vibrational natural freq of molecule radiation will be absorbed, causing a change in amplitude of molecular vibration. • Permanent dipole not necessary, only a change in dipole moment • Not all bond absorb IR . Bond must have an electric dipole (bond polarity) that changes as it vibrates. • Molecules absorb IR – cause changes in modes of vibration (stretch/bend) IR Absorption and Molecular Vibration Molecular Vibration Stretching Mode Bending Mode Symmetric Stretching • change in bond length • bond become shorter/longer • IR ACTIVE (change in dipole) • IR INACTIVE (No change in dipole) Asymmetric Stretching • change in bond length • bond become shorter/longer • IR ACTIVE (change in dipole) • IR INACTIVE (No change in dipole) Symmetric Bending • change in bond angle • bond angle bigger/smaller • IR ACTIVE (change in dipole) • IR INACTIVE (No change in dipole) Asymmetric Bending • change in bond angle • bond angle bigger/smaller • IR ACTIVE (change in dipole) • IR INACTIVE (No change in dipole) wagging twisting rocking scissoring Greenhouse Effect GHG allow short wavelength radiation to pass through but absorb IR longer wavelength radiation
- 11. Stretching Mode Bending Mode Symmetric Stretching - Bond polarity cancel out - NO change dipole moment - IR (inactive) Asymmetric Stretching - change in bond length - change dipole moment - Absorb IR (active) Symmetric Bending - change in bond angle - change dipole moment - Absorb IR (active) Molecular Vibration for CO2 IR spectrum for CO2 Click here Spectra database (Ohio State) Click here Spectra database (NIST) Molecular Vibration Click here CO2 level (NASA) Click here CO2 level (NOAA) CO2 level over time Click here CO2 level (CDIAC)
- 12. Click here CO2 level (NASA) Click here CO2 level (NOAA) CO2 level over time Click here CO2 level (CDIAC) Ocean acidification Effect of ocean acidification -Decrease in pH level - Disturb marine /coral reef development/ecosystem - CaCO3 needed for skeleton/shell for marine organisms - Reduce ability of reef building coral to produce skeleton Equilibrium bet CO2 (atmosphere) with aq CO2 (ocean) Effect of increased CO2 level Equilibrium bet CO2 (atmosphere) with aq CO2 (ocean) CO2 (g) CO↔ 2 (aq) ↓ CO2 (aq) + H2O H↔ 2CO3 (aq) ↓ H2CO3 (aq) H↔ + (aq) + HCO3 - (aq) ↓ HCO3 - (aq) H↔ + (aq) + CO3 2- (aq) H+ ion (acidic)
- 13. Carbon Capture Storage/Sequestration (CCS) i. Explain high solubility CO2 ii. Predict sign ∆H sol for CO2 in water, deduce how its solubility increase with temp iii. High level CO2 lead to positive feedback whereby increase global temp are amplified. Exp its mechanism iv. Ocean acidification is due to a drop in pH from 8.2 to 8.1. Find the % increase in acidity. Capture and storage from fossil fuel i. CO2 – polar bond, form H2 bonding with water. ii. ∆H solution –ve, due to strong H2 bonding with water (favourable) Increase in Temp- shift equi to left (endo) to reduce temp again High Temp – decrease CO2 solubility iii. High Temp – amplify the process as less CO2 dissolve – more CO2 in atmosphere – higher temp CO2 (aq) + H2O H↔ 2CO3 (aq) ∆H = -ve polar bond polar 92.8 10 10 103.610][ ][log2.8 ][log −−+ + + ×== −= −= H H HpH 91.8 10 10 109.710][ ][log1.8 ][log −−+ + + ×== −= −= H H HpH %25%100 )103.6( )109.7()103.6( %. 9 99 =× × ×−× = − −− increase H2 bonding
- 14. Acknowledgements Thanks to source of pictures and video used in this presentation Thanks to Creative Commons for excellent contribution on licenses http://creativecommons.org/licenses/ http://spmchemistry.onlinetuition.com.my/2013/10/electrolytic-cell.html http://www.chemguide.co.uk/physical/redoxeqia/introduction.html http://educationia.tk/reduction-potential-table http://2012books.lardbucket.org/books/principles-of-general-chemistry-v1.0/s23- electrochemistry.html Prepared by Lawrence Kok Check out more video tutorials from my site and hope you enjoy this tutorial http://lawrencekok.blogspot.com