Lets Set The Stage For centuries now, ever since the first gasoline powered vehicles were invented there has been a drive to find a cleaner energy source. Ever since the electric powered car was invented in 1888, it has drifted in and out of popularity for various reasons. Mostly because of limitations like: Battery Life Power (Top speed) Power (Step on the pedal and go) These problems have all been solved btw….
Gasoline Vs Electric Cars Gasoline engines are about 20% efficient…..so that means that 80% of the energy in the gas you buy is lost and pollutes the environment. By comparison electric cars are around 90% efficient. Gasoline powered engines require regular maintenance to stop problems resulting from the incomplete burning of gasoline. Electric engines require very minimal maintenance to replace things that would need replacing no matter what type of car you have.
Gasoline Vs Electric Cars The extraction of fossil fuels causes huge amounts of pollution. In fact, the CO2 pollution created by the extraction of fossil fuels in Alberta is equal to the amount of CO2 produced in the rest of Canada. The electricity that electric cars use is often produced by burning fossil fuels anyway. But you’d have a hard time finding anything in your house that is 90% efficient. Did I mention that electric engines are almost silent?
Gasoline Vs Electric CarsLets Put This In Perspective So you go and fuel up your ride….its a 60 L Tank. Lets say gas is $1.20/L…it’s a pretty good average. So it costs you ($1.20/L)(50L)= $60.00 So gasoline engines are 20% efficient… That means that out of the $60.00 to gas up you car/truck you only actually use $12.00 of it. $12.00! $48.00 just floated off as pollution. Pollution that you will eventually pay(again) to get rid of.
So Why Aren’t We Using Electric Cars? Well because their less efficient. Because their ugly. Because they aren’t ready yet, too many problems, the technology doesn’t exist yet Their too slow, we have places to be. The batteries to run the car are too heavy and not powerful enough. 85% vs 20%...right…. How a car looks has little to nothing to do with the engine. The first electric car was invented in 1888! Electric Car vs Porsche 911 Turbo Electric Cars Are Better
The BatteryThe Electric Car’s “Ball and Chain” The biggest obstacle stopping the wide spread use of electric cars is the lack of a powerful, lightweight, and inexpensive battery to power it. The old Lead-Acid battery (The big klunker you put in your car…youv probably all seen them) is: • Too Heavy • Too Weak • Doesn’t last long enough • Expensive
The Battery “Problem”Designing A Battery For The Future Designing a new battery that is lightweight, inexpensive, powerful, and long lasting would make electric powered vehicles far, far, far, farrrrrrr superior to gasoline powered vehicles. So how do we do? How does a battery work? If were going to make a new battery we kind of have to know how one works in the first place. ***A battery stores/creates electricity through a redox reaction.***
The Lead-Acid BatteryLets Make The Redox Equation Sulfuric Acid and Lead Battery. Hint: Lead and Lead Oxide H2SO4(aq) + Pb(s) + PbO2(s) H+(aq) + SO42-(aq) + H2O(l)
The Lead-Acid BatteryLets Make The Redox Equation Sulfuric Acid and Lead Battery. SOA OA OA H+(aq) + Pb(s) +PbO2(s) + H2O(l) + SO42-(aq) RA SRA RA
The Lead-Acid BatteryLets Make The Redox Equation PbO2(s) + SO42-(aq) + 4H+(aq) +2e- PbSO4(s) + 2H2O(l) SOA OA H+(aq) + Pb(s) +PbO2(s) + H2O(l) + SO42-(aq) RA SRA Pb(s) + SO42-(aq) PbSO4(s) +2e- Recharging
Taking Reactants and Creating Redox Equations To this point you have learned how to do all the steps of taking chemical reactants and creating an oxidation ½ and a reduction ½. Even more than that, you can add the two together and get an overall equation. What this unit is about, is taking that knowledge of redox reactions and using the Electrical Potential E° (V) values from your data booklet.
Allesandro Volta invented the first electric cell. Allesandro was inspired by another scientist that noticed that when he electrocuted a frog’s leg it twitched. Who said electrocuting random stuff doesn’t help you learn. You know what this means right!!? + =
Volta’s “Electric Cell” (-) (+) Anode Cathode Electrons flow from the Negative pole (Anode) to the positive pole (Cathode). Metal rods are referred to as the “electrodes” or “poles” (+) and (-). Positive(+) pole is called the cathode. Negative(-) pole is called the anode. The “flow” of electrons is called Electricity. Electrolyte solution (Salt Water/NaCl)
Volta’s “Electric Cell” Electricity created from the flow of electrons from one pole to the other was so small that it wasn’t enough to be useful. Solution?
Volta’s “Electric Cell” An electric cell does not conduct electricity unless the poles are connected together.
The Car Battery The Battery broken in 6 cells connected together in a chain.
Volt Meter The size of the battery doesn’t necessarily mean its voltage is higher. Bigger batteries can store more energy and transfer more at one time. The Volt Meter measures the electric potential difference between the cathode and the anode.
Ammeter An ammeter measures the “flow” of electrons. Bigger batteries can have the same voltage as smaller batteries, but because their bigger they can send a higher volume of that potential energy at one time. Larger volume per time means that the rate of flow from a big battery is higher. Amperage (ammeter unit) is a measure of the rate of electron flow. 1 Amp = 1 Coloumb/second
Voltage, Coulombs, AmperageVoltage Voltage is the electric potential difference between the two poles. Measures the difference between how many electrons are at the anode and how many are at the cathode. Voltage is specific to the type of battery, IT IS NOT AFFECT BY THE SIZE OF THE BATTERY! You can get a 1.5 Volt battery in any size; AAA, AA, C, D …whatever, size doesn’t matter.
Voltage, Coulombs, AmperageCoulombs Coulomb is a measure of the amount of energy stored in a battery. Coulombs are expressed as Q…..a measurement of energy only. How many coulombs of energy is dependant on the size of the battery. LIKE THE VOLUME OF A BATTERY. 2 Coulombs 800 Coulombs
Voltage, Coulombs, AmperageAmperage Amperage is the rate/speed at which electricity can flow out of the battery. Amperage is the amount of electrons/second. Amperage is Coulombs/second. 0.55 amps or 0.55 C/s. 4 amps or 4 C/s.
Voltage, Coulombs, AmperageThe “Water Tank/Hose” Analogy Voltage is determine by the type of reaction. Since both tanks hold water so the voltage is the same for both. Amperage is the rate. 115L Liter Hat Water Tank 11350 Liter Water Tank Coulombs are a measure of amount, volume in this case......115L vs 11350L. Which would have a higher “rate” of flow?
Batteries 1.5V The Zinc-Chloride battery. One of the most common and inexpensive batteries. Invented in 1865. 1.5V 1.5V 9 V 1.5V 1.5V 1.5V The common 9V D cell battery is made up of 6 seperate cells. Batteries that are sealed and can’t leak are called dry cells.
2 Types of Cells Primary Cells: A electric cell that cannot be recharged, once the chemicals in the batter react to produce electricity it can never be reversed. Carbon-Zinc Zinc-Chloride Mercury-Mercury Oxide Secondary Cells: An electric cell that can be recharged. The chemical reaction that occurs to produce electricity can be reversed if electricity is applied to the cell. Nickel-Cadmium Lithium-Ion Lead-Acid
Recharging A Battery Reverse Net Redox Equation When you charge a secondary cell the net redox reaction equation is the reverse reaction. Lead-Acid Battery PbO2(s) + SO42-(aq) + 4H+(aq) +2e- PbSO4(s) + 2H2O(l) + Pb(s) + SO42-(aq) PbSO4(s) +2e- PbO2(s) + 2SO42-(aq) + 4H+(aq)+ Pb(s) 2PbSO4(s) + 2H2O(l) Discharging Charging
Fuel Cells40-70% Efficient Operate in the exact same way as a primary electric cell. You put “fuel” into the cell (the fuel can be anything that will react to produce electricity) just like you put reactants into a battery……which are used up (cant be reversed) just like a primary electric cell. Except! In a fuel cell, its not sealed and you continuously put “fuel” into it, adding more as it get consumed by the reaction. A fuel cell never runs out and dies like a battery. As long as you keep adding fuel, it keeps going.
Hydrogen-Oxygen Fuel Cell70% Efficient Forward H2 O2 H2O (OH-) O2 H2 H2 O2 H2O
Hydrogen-Oxygen Fuel CellNET REDOX EQUATION 4. Balance electrons and add reactions together….remember to cancel out “doubles.” Back 1. List all the species present and label OA & RA. OA SOA / / / H2(g)+ OH(aq) + H2O(l) + O2(g) 2 + / / SRA RA / X2 2. Choose SOA and write its oxidation equation . 2 H2(g) 4OH(aq) → 4H2O(l)+ 4 e- O2(g) 2 H2O(l)+ 4 e-→ 4 OH(aq) 2 H2(g)+ O2(g) + 4 OH(aq) → 2 H2O(l) 3. Choose SRA and write its reduction equation. H2(g)2 OH(aq) → 2 H2O(l)+ 2 e-
Couple Other Options Possible use in electric cars. Replaceable solid aluminum fuel. High energy density. 3 moles of electrons released for each Al. Aluminum is light weight. Replace aluminum every 2500km. Same as small scale but no volume weight concern. Need longer lifetime of fuel in cells. Almost always co-generation units. Produce electricity AND heat. 90% efficient! Produce 400 Mega Watts!
or Galvanic Cells A galvanic/voltaic cell is the same as the electric cells we have looked at so far, but the two electrodes are in two different electrolytes. They split up an electric cell into two ½ reactions so they can examine each reaction (oxidation/reduction) more closely. The two “½ cells” are connected together by a “salt bridge”. There are still two metal electrodes which need to be connected by an external (wire) for the cell to function
Cu(s) Zn(s) Cu(NO3)2(aq) Zn(NO3)2(aq) ”Shorthand Notation” First Electrode(s) Electrolyte(aq) Electrolyte(aq) Second Electrode(s) = Salt Bridge = Phase Change (s)-(aq)
Describing Voltaic Cells So far we can describe how a voltaic cell has: 2 Electrodes (solid poles). 2 Electrolytes….related to the electrode. Two electrodes are connect together with a wire. The two beakers (solutions) are connected together by a “salt bridge”. But how do we know which pole is the anode and which is the cathode?
Describing Voltaic Cells Well, SOA undergoes Reduction at the Cathode. The SRA undergoes Oxidation at the Anode. Well that’s useless information….how can we tell where oxidation and reduction are happening? What’s the SRA? What’s the SOA? To determine SOA and SRA the process is the same as when you predicted redox reactions last unit.
“The Ox and The Cat” Easiest way to remember this stuff is the following analogy. “ An Ox” “Red Cat” noitcude SRA edohta xidation node SOA
Lets Try One ***Remember! The Na+ and NO3- are part of the salt bridge and are spectators……so don’t list them as species present.
Determining The SRA/SOA Cathode Anode SOA undergoes Reduction at the cathode(+V). The SRA undergoes Oxidation at the anode (-V).
Cathode Anode Lets Try One
Inert Electrodes Usually the electrodes (solids) used in a voltaic cell are related to the electrolytes used. Exp: Cu(s) for Cu2+(aq) Electrolyte Ag(s) for Ag+(aq)Electrolyte Cu(s) for Cu(NO3)2(aq)Electrolyte Zn(s) for Zn(NO3)2(aq)Electrolyte But there are powerful oxidizing and Reducing agents that aren’t related to any solid form…what electrode do you use then?
Inert Electrodes Strong oxidizing agents such as Manganate (MnO4-(aq)) or Chromate (Cr2O72-(aq ))which react in acidic environments (with H+) cannot form permanently solid (insoluble/Do not conduct electricity) electrodes. The reason why so often the electrolyte and electrode are related is because the electrolyte ions reduce at the same rate as the solid electrode oxidizes. 1:1 2:2 3:3 Ratio between the electrons transferred. The most common inert electrode is C(s). C(s) = Carbon….also called Graphite
Inert Electrodes C(s). Inert electrodes DO NOT REACT with the electrolyte. Inert electrodes are 100% spectator species. Inert electrodes only purpose is to provide an attachment for an wire to be connected to each pole so e- can flow between them.
Standard Cell Potentials Voltaic Cell Standard Cell Potential (E°) is the maximum electric potential difference between the cathode and the anode. E° specifies that the cell is under specific SATP conditions and the electrolytes each have an EXACT concentration of 1.0 mol/L. Electrodes Electrolytes
Calculating Standard Reduction Potentials We know the Standard Cell potentials of all the possible oxidation and reduction reactions. Standard REDUCTION potentials are the difference between the cathode’s Standard Cell Potential and the anode’s SCP. FORMULA: Hint: All those numbers down the side of the Reduction table in your data booklet, yah, that’s them.