hey everyone this video is on galvanic cells before you should watch this video on ganic cells I am assuming you have an understanding of metal displacement as well as oxidation and reduction equations and reactions these are commonly known as Redux reactions in the previous video on Redux reactions and metal displacement we discussed the reaction between silver ion solution and copper metal in the same be whereby the copper metal when submerged in a silveron solution will undergo oxidation by losing two electrons to form copper ions at the same time two equivalents of silver ions will undergo reduction by gaining two electrons to form silver this causes the solution to become more blue due to the formation of copper ions in the solution and also formation of silver deposits around the copper coil due to the formation of silver metal the co-occurrence of reduction and oxidation is known as Redux reaction the same reaction can take place in the context of two beakers that are collectively known as a galvanic cell in these two beakers the first Beaker contains the copper metal called a copper electrode submerged in a copper ion solution for example copper 2 nitrates this is placed right next to a second Beaker containing a piece of silver metal or silver electrode submerged in a solution of silver ion for example silver nitrates the nitrate based Solutions are typically used in the ganic cell because they make the ionic compound rather soluble the copper electrode and the silver electrode are then connected via a piece of wire that's also connected to a voltmeter which I'll discuss what it is in a short moment the connection of the two pieces of metals allows the Redux reaction that we saw previously to take place across the two beakers specifically the co metal in the copper electrode will undergo oxidation to form copper ions in a solution and lose two electrons these two electrons will then travel through the wire towards the silver electrode and when the electrons are accumulating in the silver electrode the silver ions will gain these electrons to form silver metal so we have the same reactions before but this is taking place in two separate beakers we still have oxidation in one beer and we still have reduction in the other be in a setting of a galvanic cell the electrode that is responsible for oxidation in this case the copper electrode is always known as the anode so the anode here is oxidation in the Gonic cell the reduction always occurs at the cathode in this case the silver metal is the cathode because it is submerged in a silver ion solution where reduction occurs each individual oxidation and reduction reaction has its own electric potential that we discussed in the previous video the total potential of this galvanic cell is the combination of the two Redux reactions and this can be determined by using the reduction potential table provided to you in the HC chemistry data sheets so we can see the reduction of copper 2 ions and the reduction of silver ions in this instance the silver ion indeed under goes reduction and provides a potential of 0.8 volts however the copper metal under go a reverse reaction as what's been shown here to form copper ion and two electrons this means the potential provided by the oxidation of cough metal should be netive 0.34 volts the oxidation of copper to produce copper ions and two electrons is NE 0.34 volts and the reduction of silver ions as it's shown in the reduction potential table provides a potential of 0.8 volts the total standard potential of this garban ex cell combining the two beakers and the two Redux reactions together will be the sum of the two individual potentials which will be 0.46 volts the voltmeter that we connected using the wires to the two pieces of metal will show you the total potential of the galvanic cell in this instance the 0.46 volts is due to to the combination of the two potentials of the copper oxidation and silver ion reduction so the voltmeter measures the total potential of a galenic cell I want to quickly explain what it means by standard potential in the reduction potential table all the potential values of these reduction equations are known as standard reduction potentials standard potentials are values of these reactions measured under what we call stand standard conditions standard conditions are comprised of three things firstly it involves the use of one mole per liter Solutions at both the anode and cathode beers so the copper ion and silver ion solution that we saw in the previous example must be exactly one more per liter for it to be classified as a standard condition in addition the standard potential is measured at exactly 298 K or 25° c a room temperature and the pressure must be one atmosphere pressure or approximately 100 kilopascals all three of these conditions must be met for the potential to be measured as the standard potential if any of these factors is different to the one shown then the potential value measure will differ from the potential values provided by the standard reduction potential table so in cases where you're constructing a galbanic cell and measuring the potential of the cell in experiment and wonder why it's different to the calculate value from the table think about whether any of these three conditions is different to the standard condition so let's have a look at the diagram of this ganic cell of copper and silver again we explained that the copper metal under goes oxidation by losing two electrons and forming more copper ions in his respective solution these electrons will then flow across the wire through the voltmeter to the other known as a reduction half cell whereby the silver ions in the solution will come in contact with these electrons and hence undergo reduction to form silver metal collectively the anode and the copper ion solution in the oxidation Bea is known as the oxidation half cell and the silver electrode and its silver ion solution are collectively known as a reduction half cell the electron flow in a Gonic cell always is direct directed from the anode and flows towards the cathode the electric potential generated by the two oxidation and reduction equations causes the anode to have a to acquire negative charge and the cathode to acquire a positive charge another way you can understand the two charge differences is to remind yourself that electrons are negatively charged in order for the electrons to move from the anode to the cathode they must be drawn and attracted towards the the positive charge of the silver cathode and at the same time it should be repelled away from the negatively charged copper anode so just to reiterate the anode has a negative charge and the cathode in the Carbonic cell has a positive charge and the direction of electron flow goes from the anode towards the cathode goes from the oxidation half cell towards the reduction half cell now understanding the initial charge differences between the oxidation and reduction Hales of is important because this will help us understand the changes in charge as more electrons flow from the anode towards the cathode over time as this galvanic cell operates more and more electrons will accumulate at the cathode electrons are negatively charged so the accumulation of more electrons will decrease the positive charge of the cathode and at the anode as more electrons are flowing across the wire away from the anode the negative charge will also decrease because we're losing electrons at the anode in other words as the electrons flow from the oxidation to the reduction half cell the anode becomes less negative and the cathode becomes less positive this will gradually decrease the difference in charge between the two electrodes and the two half cells eventually the two charges will both become the same at which point the electric potential between the two half cells will tend towards Z volts and at this point the electron flow will stop so how do we overcome this problem how do we maintain the electron flow such that the charge difference between the anode and the cathode Remains the Same as what it was in the beginning this is where the salt bridge of the Gabon EXO comes into play a so Bridge is a piece of material that contains so cations and anion and is connected to the electrolyte Solutions of the two half cells this connection is made so that the ions are free to move into the electrolyte Solutions recall that as the electrons flow from the anode towards the cathode the anode becomes less negative due to the loss of electrons and in a solution it becomes more positive due to the accumulation of positive copper ions this accumulation of positive charge will attract the negative anion from the sulage into the solution because negative charges are attracted towards positive charges at the same time as the electrons accumulate in the cathode the positive charge of the cathode will decrease and as more silver ions are reduced by gaining these electrons the positive charge in the electrolyte solution will decrease and therefore the the negative charge of the solution will increase because there will be more annion compared to positive silver ions the accumulation of negative charge in the cathode electrolyte solution will attract positive sodium ions into the cell so we have negative anion such as nitrate flowing into the oxidation half cell positive cat like sodium flowing into the negatively charged reduction half cell the migration of these ions on the salt bridge will neutralize the charges in the respective beakers so that the oxidation beer can maintain its initial negative charge and the reduction beer half cell can maintain its positive charge the salt bridge usually contains a very soluble ion such as sodium nitrate so that the ions are free to move into these respective electrolyte Solutions therefore the salt bridge is to maintain Electric neutrality in the Solutions in the initial electrical potential of the Gonic cell by achieving this we can maintain the flow of electrons from the anode to the cathode this is what a setup of a galvanic cell looks like in a school laboratory we have two beakers each representing an oxidation and reduction half cell in the two solutions we have two pieces of electrode one is an anode and one is the cathode in this image you can see that the two electrodes are are connected to a voltmeter in the middle via wires these wires will help the electron to flow from the anode to the cathode and the voltmeter in the middle will measure the electric potential between the two half cells in most diagrams the salt bridge is drawn as a glass tube that contains the ionic solution with pores on both ends that allow the ions to flow into the respective electric Solutions however in most school experiments we can replace the glass soap Bridge with a simple filter paper that is soaked inside an ionic solution such as sodium or potassium nitrates in this picture we have a potassium nitrate soaked piece of filter paper that is bent into a bridge shape so that's it's connecting the two electrolyte Solutions in the two half cells in certain ganic cells there are noticeable observations you can see besides the potential reading in the volt meter for example in the copper and silver Carbonic cell as the copper electrode underes oxidation to form copper ions and electrons the mass of the copper anode will decrease over time because copper atoms are being oxidized to form copper ions the formation of copper ions in a solution will increase the concentration of copper 2+ ions copper 2 plus ions typically will appear as a blue solution so an increase in its concentration will make the solution in the oxidation half cell more blue as The Silver ions are gaining electrons in the reduction half celf to form more silver deposits around the silver cathode the mass of the silver cathod will increase over time so you might be wondering why are we learning about Redux reactions in a setting of galvanic cells well galvanic cells are applications of Redux reactions they convert chemical energy that's stored inside Redux reactions into movement of electrons across the wire in the form of electrical energy so they convert chemical energy into electrical energy that we can further harness in numerous applications such as car batteries so ganic cells generate electrical energy via the use of Redux reactions ganic cell notations provide a simple way to represent the composite position of a Gonic cell without having to draw a complicated diagram such as this one we've been using in the video in the standard in the conventional ganic cell notation we always represents the oxidation half cell first firstly we write down the anode which is the electrode in the oxidation half cell in this case it's copper metal so CU solid and we separate the anode with the electrolyte solution involved in the oxidation half cell by a vertical line the copper atom oxidizes to from copper ion so we write the copper ion next to the Copper separated by a vertical line collectively this is your oxidation half cell this is Then followed by a double vertical line in the middle of the notation representing the salt bridge which should always be present in the Gonic cell to maintain electron flow and electric potential after the salt bridge we'll write the respective ion in the reduction half cell in this case it's silver ion and then this is followed by the cathode which is silver electrode separated by a vertical line and collectively the right hand side of the notation represents the reduction half cell so the oxidation half cell is always written first on the left hand side of notation followed by the reduction half cell and in between the two half cells we have double vertical lines representing the Sal bridge in ganic notations we typically use a sing single vertical line to separate species of Redux reactions from different states this is why the solid electrodes are separated by the Aquis ions by vertical lines if there are multiple species in the Redux reaction of the same States will use a comma instead of a vertical line to separate them in the notation it is good practice to include the concentration of acis species in the Carbonic cell if you know them because the concentration of the species will determine the potential of the cell if this Gonic cell was set up at standard conditions then the copper and silver ions will be both one mole per liter in concentration let's go through another example of a Gonic cell to summarize everything we've learned in this video so a Gonic cell is constructed using nickel and zinc Metals as electrodes as well as Niel ions and zinc ion Solutions this is a simple diagram representing the setup before you answer any question regarding a Gonic cell the first thing you should do is to determine what the oxidation and reduction reactions are in your Gonic cell to do this we need to find the respective reduction equations and Potentials in the reduction potential table this is a snippet of the reduction potential table from the HSC data sheets so let's look for zinc and nickel so here we have have the reduction of zinc ions and this is the reduction of nickel 2 plus ions the reaction that has a higher potential will undergo reduction so the nickel ion has a higher potential so this will be a reduction equation and the equation with the smaller potential will undergo oxidation so the zinc metal here will be oxidized to form zinc ion and of course we have to reverse the potential for oxidation of zinc so be plus 0.7 six so let's write down what we just determined the oxidation reaction for this Carbonic cell will be the oxidation of zinc metal to form zinc 2 plus ion and two electrons at the same time the reduction equation is nickel ion gaining two electrons to form nickel atom or metal once you've determined the oxidation reduction equation we can then answer rest of the questions with ease part A identify the anode and cathode and the direction of electron flow so by convention the anod is the electrod of the oxidation half cell in this case that's the zinc so zinc metal is the anode and then nickel which is a reduction electrode will be the cathode the direction of electron flow always goes from the anode in oxidation Beaker to the cathode in the reduction beer so it go from the zinc to the nickel like this that's the electron Flow Part B calculate the total standard potential so we already determined that the potentials of each of the Redux reactions are as follows positive 0.76 and minus 0.24 so the total standard potential eot will be 0.76 - 0.24 and this gives you a total value of 0.52 Vols part C identify the direction of flow of ions in the salt bridge so recall that the anode in the Gonic cell has an initial negative charge and the cathode has an initial positive charge which is the reason why the electrons will flow from the anode to the cathode from the negative charge towards the positive charge now over time as the electrons will flow from the an to the cathode this positive charge will decrease and this negative charge will also decrease so the cathode or the reduction half cell becomes more negative and the anode or the redu or the oxidation half cell will become more positive as the electrons are leaving it the role of the salt bridge is to maintain the electrical neutrality by neutralizing the accumulation of these charges so the cation for example sodium ion will flow into the reduction half cell to neutralize the more negative charge simultaneously the negative anion for example nitrate will flow into the anode or the oxidation half cell to neutralize a more positive charge so cation flow into the reduction half cell the anion will flow into the oxidation half cell part D write the Shand notation for this Gonic cell so recall that for Shand notation Gonic cells we always write the oxidation half cell first this starts with the anode which is a zinc solid vertical line to separate the zinc solid from the zinc ions zinc 2+ that's why the AQ this this is the oxidation half cell and then this is Then followed by the reduction half cell after Double vertical lines for the salt bridge the electrolytes in the reduction half cell which are the nickel 3 plus ions and then this is Then followed by one vertical line and the Cod which is a nickel solid so we always always write the oxidation half cell first followed by the reduction half cell this concludes the video on ganic cells hey everyone if you found this video helpful smash that like button and don't forget to subscribe one even more become a patreon member for Early Access to videos exclusive Discord discussions about questions on chemistry and physics and live preparation sessions for your exams don't forget to head over to our website for topic tests and practice exams to further improve your understanding and learning