Energy PDF

IT2310 ENERGY Energy is the ability to do work. It is essential for all life on Earth, and we use it to power our homes, businesses, and transportation. Energy can be found in many different forms, including kinetic energy, potential energy, elec...

IT2310 ENERGY Energy is the ability to do work. It is essential for all life on Earth, and we use it to power our homes, businesses, and transportation. Energy can be found in many different forms, including kinetic energy, potential energy, electrical energy, chemical energy, nuclear energy, and radiant energy. Energy is essential for our modern way of life. We use it to power our homes, businesses, and transportation. We also use it to produce goods, manufacture products, and provide services. However, our reliance on energy also harms the environment. Burning fossil fuels, such as coal, oil, and natural gas, releases greenhouse gases into the atmosphere, contributing to climate change. We need to find ways to reduce our energy consumption and use renewable energy sources, such as solar and wind power, to meet our energy needs. Fuels (Dk, 2020) When a chemical reaction between a fuel and oxygen (or air) to produce a potential difference occurs, a fuel cell is created. The fuel is oxidized, but unlike combustion, the reaction is electrochemical. The potential difference causes a current to flow when the fuel cell is part of a complete circuit, which can be used to power an electric motor. Fuel cells Batteries The potential difference stays the same while The potential difference gradually decreases the fuel cell is working. over time with use. Lasts a long time due to large reserves of fuel Have small reserves of chemicals; must be recharged or disposed of. Cannot be recharged Many are disposable, and some are rechargeable. Expensive Cheap Table 1. Comparing Fuel Cells and Batteries Figure 1. A hydrogen-oxygen fuel cell 04 Handout 1 *Property of STI  [email protected] Page 1 of 15  IT2310 At the anode (negative electrode) in a hydrogen-oxygen fuel cell, hydrogen is oxidized to hydrogen ions and electrons. The ions reach the other side of the cell through a membrane, and the electrons flow there through an external circuit. At the cathode (positive electrode), oxygen reacts with hydrogen ions and electrons and is reduced to water. Electrochemical Processes (Gaffney & Marley, 2017) Areas of Application: REDUCTION – OXIDATION REACTIONS Redox Reactions are a group of reactions involving electron transfer, with each individual reaction referred to as half-reactions. REDUCTION is the process of gaining free electrons, catalyzed by reducers (aka reducing agents, reductants) Examples: 𝑂2 , 𝑂3 , 𝐹2 , 𝐶𝑙2 , 𝐵𝑟2 , 𝐻2 𝑆𝑂4 , 𝐻𝑁𝑂3 2+ 0 𝑍𝑛(𝑎𝑞) + 2𝑒 − → 𝑍𝑛(𝑠) OXIDATION is the process of losing electrons, catalyzed by oxidizers (aka oxidants, oxidizing agents) Examples: 𝑍𝑛, 𝐻𝑔, 𝑆𝑛, 𝑀𝑔, 𝐴𝑔, 𝐴𝑙, 𝑀𝑛 0 2+ 𝑍𝑛(𝑠) → 𝑍𝑛(𝑎𝑞) + 2 𝑒− Oxidation number (ON) Rule Substance Examples The ON of an atom is zero in a neutral substance that contains atoms of only one Noble gases, 𝐶𝑙2 , 𝐹2 , 𝑂2 , 𝐻2 , and 𝑆8 element. Monoatomic ion’s ON is equal to its charge. 𝐶𝑎2+ → ON of +2 𝑁𝑎 → ON = (+1), 𝐶𝑙 − →ON = (-1) + The oxidation number of hydrogen is +1 CH4, NH3, H2O, HCl…→ ON of H = (+1) when it is combined with a nonmetal. The oxidation number of hydrogen is -1 when LiH, NaH, CaH2, LiAlH4… → ON of H = (-1) it is combined with a metal. The metals in Group IA that form compounds Li3N, Na2S have an oxidation number of +1. The elements in Group IIA form compounds Mg3N2 and CaCO3 have a +2-oxidation number. The elements in Group VIIA often form compounds in which the nonmetal has a -1 AlF3, HCl, and ZnBr2 oxidation number. Neutral compounds have a total of zero (0) H2 O, NaCl(aq) , C6 H12 O6 (aq) ON. Oxygen usually has an oxidation number of -2. Exceptions include molecules and polyatomic O2, O3, H2O2, and the O22- ion. ions that contain O-O bonds. Alkali elements have an ON of +𝟏, including H, Li, Na, K, Rb, Cs, Fr lone hydrogen Alkali earth elements have an ON of +𝟐 Be, Mg, Ca, Sr, Ba, Ra 04 Handout 1 *Property of STI  [email protected] Page 2 of 15  IT2310 The sum of the oxidation numbers in a neutral H2O: 2(+1) + (-2) = 0 compound is zero. Table 2. Rules of Oxidation Numbers Annotations in Oxidation Numbers 1. Neutrality is the basis for determining the oxidation numbers of certain elements in a compound. a. This is how oxygen (𝑂2− ) has various oxidation numbers despite having an ON of −2, depending on the compound. In peroxides, oxygen’s ON is −1, whereas it has an ON of +1 if oxygen is bonded with fluorine. b. Hydrogen becomes −1 if bonded as binary metal hydrides (e.g., 𝑁𝑎𝐻). It retains its +1 ON if it’s bonded to nonmetals. 2. Fluorine’s ON is always −1. Unpaired chlorine, bromine, and iodine usually have an ON of −1 unless bonded to either oxygen or fluorine. 3. Polyatomic ions (i.e., 𝑁𝑂3 , 𝑆𝑂4 ) have their ON values equal to their anionic charges. 4. Certain groups yield certain oxidation numbers (see table below). Areas of Application: ELECTROLYSIS The electrochemical process of allowing electrical current to pass through ionized material suspended in an electrolyte. This allows for nonspontaneous reactions to occur. Standard Reduction Potential from Electrolysis: ° ° ° 𝐸𝑐𝑒𝑙𝑙 = 𝐸𝑐𝑎𝑡ℎ𝑜𝑑𝑒 − 𝐸𝑎𝑛𝑜𝑑𝑒 Thermodynamics of Redox and Electrolysis: Given the electrical energy in joules, as discussed in Physics, 𝐸 = 𝑞𝑉 Where 𝑞 = charge in coulombs and 𝑉 = voltage in volts. It is well understood that the value of 𝑞 is derived from, 𝑞 = 𝑛𝑒 − Where 𝑒 − = charge of an electron (1.6022 × 10−19 𝐶), and 𝑛 = number of electrons present. It is more convenient in chemistry to present the total charges in molar quantities. A charge of one mole of electrons is called the Faraday constant (ℱ), where, 1 ℱ = (6.022 × 10−23 𝑒 − /𝑚𝑜𝑙) × (1.6022 × 10−19 𝐶/𝑒 − ) 1 ℱ = 96, 500 𝐶/𝑚𝑜𝑙 = 9.65 × 104 𝐶/𝑚𝑜𝑙 This means that the total charge can be expressed as 𝑛ℱ, where 𝑛 = number of moles of electrons transferred between reducing and oxidizing agents during the overall redox reactions. It has also been established that a dry cell’s electromotive force (𝐸𝑐𝑒𝑙𝑙 ) is the maximum voltage that a cell can achieve. 04 Handout 1 *Property of STI  [email protected] Page 3 of 15  IT2310 Therefore, to determine the Gibbs free energy (∆𝒢), sometimes referred to as maximum work (𝑊𝑀𝐴𝑋 ) or electrical work (𝑊𝐸 ), 𝑊𝑀𝐴𝑋 = 𝑊𝐸 = ∆𝒢 ∆𝒢 = −𝑛ℱ𝐸𝑐𝑒𝑙𝑙 If the reaction is spontaneous, ∆𝒢 is negative. Because both 𝑛 and ℱ are positive quantities, the rule of thumb follows that 𝐸𝑐𝑒𝑙𝑙 is also positive. For reactions where both reactants and products are in their standard states (i.e., in 1 M or 1 atm values), ∆𝒢 becomes, ∆𝒢° = −𝑛ℱ𝐸°𝑐𝑒𝑙𝑙 (1) Where 𝐸°𝑐𝑒𝑙𝑙 = emf at standard reduction potential. From here, 𝐸°𝑐𝑒𝑙𝑙 can be related to the equilibrium constant (𝒦) of a redox reaction, where, 𝑟𝑒𝑑𝑢𝑐𝑒𝑑 𝑖𝑜𝑛 𝑖𝑛 𝑚𝑜𝑙𝑎𝑟 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 𝒦= 𝑜𝑥𝑖𝑑𝑖𝑧𝑒𝑑 𝑖𝑜𝑛 𝑖𝑛 𝑚𝑜𝑙𝑎𝑟 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 Where the reduced ion is the ion outside the cell, while the oxidized ion is the ion within the cell. In chemistry, the free energy in thermodynamics is represented by the relationship, ∆𝒢 = ∆𝒢° + 𝑅𝑇 ln 𝒬𝑐 Where 𝑅 = gas constant (8.314 𝐽 ∙ 𝑚𝑜𝑙/𝐾), 𝑇 = absolute temperature of the reaction, and 𝒬𝑐 = reaction quotient. This means that, as ∆𝒢° increases or decreases (be it in positive or negative value), ∆𝒢 values follow accordingly. This makes 𝑅𝑇 ln 𝒬𝑐 the counterbalance of the equation to make the equation in equilibrium. This makes the value of 𝑄𝑐 become 𝒦. At ∆𝒢 = 0, this shows that, ∆𝒢° = −𝑅𝑇 ln 𝒦 (2) Combining both equations 1 and 2 to derive the electromotive force of a cell at standard reduction potential (at 25℃ or 298 𝐾), −𝑛ℱ𝐸°𝑐𝑒𝑙𝑙 = −𝑅𝑇 ln 𝒦 𝑅𝑇 𝐸°𝑐𝑒𝑙𝑙 = − ln 𝒦 −𝑛ℱ 𝑅𝑇 𝐸°𝑐𝑒𝑙𝑙 = ln 𝒦 𝑛ℱ (8.314 𝐽/𝐾 ∙ 𝑚𝑜𝑙)(298 𝐾) 𝐸°𝑐𝑒𝑙𝑙 = ln 𝒦 𝑛(96, 500 𝐶/𝑚𝑜𝑙) 𝟎. 𝟎𝟐𝟓𝟕 𝑽 ∴ 𝑬°𝒄𝒆𝒍𝒍 = 𝐥𝐧 𝓚 𝒏 In base-10 logarithmic, 𝟎. 𝟎𝟓𝟗𝟐 𝑽 𝑬°𝒄𝒆𝒍𝒍 = 𝐥𝐨𝐠 𝓚 𝒏 04 Handout 1 *Property of STI  [email protected] Page 4 of 15  IT2310 The equilibrium constant dictates the reactions under standard-state conditions, as seen in the chart below. ∆𝓖° 𝓚 𝑬°𝒄𝒆𝒍𝒍 Favored Reaction Negative >1 Positive Formation of products only Neutral (i.e., zero) =1 Neutral (i.e., zero) Both reactants and products Positive 200) into smaller, stable constituent element by-products and neutrons, releasing high amounts of energy due to the product’s instability FORMULA: 𝑋𝑍A + 10𝑛 → 𝑋𝑍B + 𝑋𝑍𝐶 + 𝑥 10𝑛 + γ Where, 𝐴 = Parent nucleus 𝐵 & 𝐶 = constituent element nuclei formed after fission 1 0𝑛 = neutron 𝑥 = numerical coefficient of neutrons γ = energy Example: 235 1 92U + 0𝑛 → 90 143 1 38Sr + 54𝑋𝑒 + 3 0𝑛 + γ NOTE: Nuclear fission may form any constituent elements during the process if the products have the same values as the original materials. 04 Handout 1 *Property of STI  [email protected] Page 11 of 15  IT2310 Addendum: 𝑈𝑟𝑎𝑛𝑖𝑢𝑚 typically releases three (3) neutrons during fission per nucleus. o 𝑈 − 233 yields three (3) neutrons o 𝑈 − 235 yields two (2) to three (3) neutrons o 𝑈 − 238 yields three (3) neutrons 𝑃𝑙𝑢𝑡𝑜𝑛𝑖𝑢𝑚 releases three (3) neutrons during fission per nucleus. All of Plutonium’s isotopes (i.e. 𝑃𝑡 − 238, 𝑃𝑡 − 239, 𝑃𝑡 − 240, 𝑃𝑡 − 241, 𝑃𝑡 − 242) yield three (3) neutrons. 𝑇ℎ𝑜𝑟𝑖𝑢𝑚 − 232 releases two (2) neutrons during fission per nucleus. 𝐶𝑎𝑙𝑖𝑓𝑜𝑟𝑛𝑖𝑢𝑚 − 252 typically releases four (4) neutrons during fission per nucleus. 𝐴𝑚𝑒𝑟𝑖𝑐𝑖𝑢𝑚 − 241 typically releases three (3) neutrons during fission per nucleus. 𝐶𝑢𝑟𝑖𝑢𝑚 typically releases three (3) neutrons during fission per nucleus. o 𝐶𝑚 − 242 yields three (3) neutrons o 𝐶𝑚 − 243 yields three (3) neutrons o 𝐶𝑚 − 244 yields three (3) neutrons o 𝐶𝑚 − 245 yields three (3) to four (4) neutrons Nuclear Chain Reaction Self-sustaining sequence of nuclear fission reactions Critical Mass Minimum mass required for the fissionable material to generate a self-sustaining chain reaction Fusion combining of several atoms with small nuclei into a larger by-product, releasing higher amounts of energy; aka thermonuclear reaction Green Energy (What Is Green Energy? (Definition, Types and Examples), n.d.) Green energy is any energy type that is generated from natural resources, such as sunlight, wind, or water. As a source of energy, green energy often comes from renewable energy technologies such as solar energy, wind power, geothermal energy, biomass, and hydroelectric power. Each of these technologies works in different ways, whether that is by taking power from the sun, as with solar panels, or using wind turbines or the flow of water to generate energy. Renewable Energy vs. Green Energy Renewable Energy - is energy that comes from sources that are constantly replenished, such as the sun, wind, and water. Renewable energy sources are sustainable, meaning that they can be used without running out. Green Energy - To be deemed green energy, a resource cannot produce pollution, such as is found with fossil fuels. This means that not all sources used by the renewable energy industry are green. For example, power generation that burns organic material from sustainable forests may be renewable, but it is not necessarily green due to the CO2 produced by the burning process itself. 04 Handout 1 *Property of STI  [email protected] Page 12 of 15  IT2310 Green energy sources are usually naturally replenished, as opposed to fossil fuel sources like natural gas or coal, which can take millions of years to develop. Green sources also often avoid mining or drilling operations that can be damaging to ecosystems. Types of Green Energy Solar Power This common type of renewable energy is usually produced using photovoltaic cells that capture sunlight and turn it into electricity. Solar power is also used to heat buildings, hot water, cooking, and lighting. Solar power has now become affordable enough for domestic purposes, including garden lighting, although it is also used on a larger scale to power entire neighborhoods. Wind Power Particularly suited to offshore and higher altitude sites, wind energy uses the power of air flow around the world to push turbines that generate electricity. Hydropower Also known as hydroelectric power, this type of green energy uses the flow of water in rivers, streams, dams or elsewhere to produce electricity. Hydropower can even work on a small scale using water flow through pipes in the home or can come from evaporation, rainfall, or the ocean's tides. Exactly how ‘green’ the following three types of green energy are depends on how they are created. Geothermal Energy This type of green power uses thermal energy stored just under the earth’s crust. While this resource requires drilling to access, thereby calling the environmental impact into question, it is a huge resource once tapped into. Geothermal energy has been used for bathing in hot springs for thousands of years, and this same resource can be used for steam to turn turbines and generate electricity. The energy stored in the United States alone is enough to produce 10 times as much electricity as coal currently can. While some nations, such as Iceland, have easy-to-access geothermal resources, it is a resource that relies on location for ease of use, and to be fully ‘green,’ the drilling procedures need to be closely monitored. Biomass This renewable resource also needs to be carefully managed to be truly labeled as a ‘green energy’ source. Biomass power plants use wood waste, sawdust, and combustible organic agricultural waste to create energy. While burning these materials releases greenhouse gases, these emissions are still far lower than those from petroleum-based fuels. Biofuels Rather than burning biomass, as mentioned above, these organic materials can be transformed into fuels such as ethanol and biodiesel. Having supplied just 2.7% of the world’s fuel for transport in 04 Handout 1 *Property of STI  [email protected] Page 13 of 15  IT2310 2010, biofuels are estimated to have the capacity to meet over 25% of global transportation fuel demand by 2050. Green Energy Solutions Heating and Cooling in Buildings Green energy solutions are being used for buildings ranging from large office blocks to people’s homes. These include solar water heaters, biomass-fuelled boilers, direct geothermal heat, and cooling systems powered by renewable sources. Industrial Processes Renewable heat for industrial processes can be run using biomass or renewable electricity. Hydrogen is now a large provider of renewable energy for the cement, iron, steel and chemical industries. Transport Sustainable biofuels and renewable electricity are growing in use for transportation across multiple industry sectors. Automotive is an obvious example as electrification advances to replace fossil fuels, but aerospace and construction are other areas that are actively investigating electrification. Writing References Bauer, W., & Westfall, G. D. (2016). General physics 2 (2nd ed.). Quezon City: ABIVA Publishing House. Boston University (n.d.). Nuclear binding energy and the mass defect. Retrieved from http://physics.bu.edu/~duffy/sc546_notes10/mass_defect.html Brilliant (n.d.). Electrolytic cells and electrolysis. Lifted and modified from https://brilliant.org/wiki/electrolytic-cells-and-electrolysis/#laws-of-electrolysis Cacanindin, D.D.A., …, Sharma, M. PhD (2016). General physics 2. Quezon City, Vibal Publishing House, Inc. Chang, R., & Goldsby, K. A. (2016). Chemistry (12th ed.). New York: McGraw-Hill. Dk. (2020). Super simple chemistry: The Ultimate Bitesize Study Guide. National Geographic Books. Dummies (n.d.). Rules for assigning oxidation numbers to elements. Lifted and modified from http://www.dummies.com/education/science/chemistry/rules-for-assigning-oxidation-numbers-to- elements/ Freedman, R. A., Ford, A. L., & Young, H. D. (2012). Sears and Zemansky's university physics (with Modern physics) (13th ed.). Addison-Wesley. Gaffney, J., & Marley, N. (2017). General Chemistry for Engineers. Elsevier. International Atomic Energy Agency (n.d.). Average number of neutrons emitted per fission. Retrieved from https://www-nds.iaea.org/sgnucdat/a6.htm Integrated Publishing, Inc. (n.d.). Calculation of fission energy. Retrieved from http://nuclearpowertraining.tpub.com/h1019v1/css/Calculation-Of-Fission-Energy-83.htm Nave, C.R. (2016). Radioactive Half-life. Retrieved from the Georgia State University HyperPhysics Classroom: http://hyperphysics.phy-astr.gsu.edu/hbase/Nuclear/halfli.html#c1 04 Handout 1 *Property of STI  [email protected] Page 14 of 15  IT2310 Oklahoma City Community College (n.d.). Assigning oxidation numbers. Lifted and modified from http://www.occc.edu/kmbailey/chem1115tutorials/oxidation_numbers.htm Petrucci, R. H., Petrucci, R., Herring, F. G., Madura, J., & Bissonnette, C. (2017). General Chemistry: Principles and Modern Applications. Pearson Education. Shodor (2008). Nuclear chemistry. Lifted and modified from http://www.shodor.org/unchem/advanced/nuc/ Tutors 4 You (n.d.). Faraday’s laws of electrolysis. Retrieved from http://tutors4you.com/Faradayslawsofelectrolysis.htm What is Green Energy? (Definition, Types and Examples). (n.d.). https://www.twi- global.com/technical-knowledge/faqs/what-is-green-energy#HowDoesGreenEnergyWork What is Green Energy? (Definition, Types and Examples). (n.d.). https://www.twi-global.com/technical- knowledge/faqs/what-is-green-energy#HowDoesGreenEnergyWork Williams, L. D. (2011). Chemistry Demystified (2nd ed.). New York: McGraw-Hill. 04 Handout 1 *Property of STI  [email protected] Page 15 of 15