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Crash Course Chemistry
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Added Jun 05, 2020
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Electrochemistry, multi-disciplined: electricity and chemistry.
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the controlled flow of electrons making possible laptops and phones and cars and pacemakers batteries just like everything else in life is just chemistry raised to the power of awesome that happens inside of a battery is called electrochemistry because it involves reactions that produce or consume free electrons or redox reaction electrons are exchanged a redox reactions before and if you haven't seen that episode yet you spray we go watch that before you watch this no worry I will still be here when you get back on the flow of electrons in these kind of reactions are sent through a conductor like a piece of metal used to do all sorts of work like for example this kind of work if I was at work that can be done depends on how strong the post or pull on electrons is between the two reactants is the reactions electrical potential voltage basically if the voltage is John can do a lot more work than if the voltage is low many of the wonderful things in our lives are based on putting a device that donates electrons and the half of it except coolest things you've done today up to and including watching this episode of Crash Course chemistry has been made possible part of what makes redox reaction so powerful and powerfully excellent is that they are complicated things going on as a part of the reaction where the electrons are being released so when we do it electrochemistry we usually think of reaction in terms of half reaction let's start with the typical redox reaction that happens in this alkaline battery is an example of blank is going through is manganese III oxide and zinc oxide I have reactions first you have elemental zinc with an oxidation number of zero being oxidized reduced to manganese 3 electrons are released during the oxidation of a zinc atom and one electron is consumed by each manganese for out of the water and hydroxide ions by the way come from the solution of potassium hydroxide which is a basic or alkaline compound which is why you think alkaline batteries nothing to these half reactions occurred in check with the other one they just spontaneously go to equilibrium releasing energy is a bunch of heat which wouldn't be very helpful reactions from each other this allows excess electrons to build up in the negative terminal call the cathode electron vacuum of sorts occurs in the positive Terminal Reaction to the other only when we connect the cathode and anode of the doctors so the current can be used to do work which I do by licking us 9 volt battery I mean battery is the zinc is in the center surrounded by a layer of cellulose that allows ions to pass through the manganese oxide is in the outer layer that surrounds cellulose barrier doesn't allow the zinc in the manganese to make my batteries are a type of galvanic cell which is generally defined as an apparatus and generates electrical energy from redox reaction an Excel one with the interesting part is the flow of hole instead of the flow of electrons in this case wires connect metal rods that are suspended in the solution are the anode and cathode used up from the anode rod as they're oxidized and slowly wears away meanwhile the opposite happens at the cathode Rod Where Metal ions from the solution gain electrons in precipitate on to the cathode as pure metal gradually growing larger by the wire but also by a salt bridge which is off the u-shaped tube that contains the salt solution that allows the metal ions to go from the anode to the cathode batteries worked before any redox reaction can be used to text your find a girlfriend or whatever we need to know how much voltage it can generate is already known and can be found in most textbooks online and as I mentioned earlier just a way of expressing the electrical potential of each half reaction the difference between mechanical demand for the electrons in 1/2 versus the tendency to lose them in the other rooms are down at standard conditions which we just got to the end for being in and by convention there written as if the substance is being reduced not oxidized reason the value is known as the standard reduction potential of a substance that can combine in overall reaction let's go galvanic cell where is zinc is oxidized and copper ions are reduced the potentials are determined at standards Solutions of the copper and zinc ions are cell needs to be set up under the same conditions or the voltage will be different than expected Behavior actions show more clearly with the electrons are doing we can see that this thing is oxidized in the copper is reduced now all standard reduction potentials which is that at zero just as a Baseline copper is reduced for example of generates 0.34 volts more than hydrogen does so we say it's standard reduction potential is + 44 volts is -0.76 volts but because pink is dies in this reaction we can't use the reduction potential directly for the reduction potential of zinc becomes positive 0 7 6 volt for the oxidation potential of zinc ions reaction called the standard cell potential of the standard potentials of goat half reactions in this case that would be 1.1 volt electrical potential of a redox reaction is related to an equilibrium constant actually a way to determine the equilibrium constant from a measured voltage at the reaction can release or it's in Gibbs free energy and breathe the higher the voltage of the more electrical energy can be produced so if the voltage is positive it means that under standard State conditions the reaction will spontaneously go forward if the sign is negative feedback word totally make sense when you think about it actions like this are used to make battery cells the reactions in batteries need to be spontaneous because their whole purpose is to release energy not consummate so what if we don't want the power of what if instead we want to play tonight car bumper with chrome cannot be done with a different electrochemical process in a solution that contains an excess of ions of the co metal a bar of the coating metal in this case chromium is used as the anode and the item to be plated of the iron bumper Steven solution and atoms of the coating metal nard. David on the cathode is essentially the opposite of a galvanic cell known as an electrolytic cell and electrolysis in this case molecules in the solution are being broken. so that the metal atoms can be deposited on a surface water into hydrogen gas and oxygen I understand how much impact chemistry has on our daily lives you certainly should be able to see it now devices that power Our Lives depend on the reactions of electrochemistry if you were listening you learned that electrochemical reactions are redox reactions that we described in terms of half reactions your battery works and what's inside of it what a galvanic cell is you then how it can be set up and how to calculate the foods that can be generated by a half reaction the standard reduction potentials and by the overall reaction the standard cell potential by eating Gonzales and edited by Blake Colton the doctor Heckle and it was filmed edited and directed by Nicholas Jenkins Michael Ronda is our sound designer and thought Cafe is our Graphics team
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