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let's talk about the chemical process of
00:00:03
electrolysis I wanted to try to write
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the simplest definition that I could so
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here's what I came up with electrolysis
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is a process where electricity is used
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to make a chemical change happen that
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wouldn't happen otherwise so we have
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some kind of a chemical change that
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doesn't happen on its own but then we
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can use electricity to make that
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chemical change happen now electrolysis
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is often used to take a compound and
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break it apart into the elements that
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make it up we'll look at two examples of
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that in this video first we'll look at
00:00:43
sodium chloride being broken apart by
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electrolysis into sodium metal and
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chlorine gas and just FYI this is an
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unbalanced equation then we'll look at
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an example of water being broken apart
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using electrolysis into hydrogen gas and
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oxygen gas so let's get started by
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taking a look at this reaction so here's
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unbalanced equation for the electris of
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sodium chloride now sometimes people ask
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me why is a cl2 and not CL well that's
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because CL chlorine is one of the
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datomic elements these are the diatomic
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elements and the diatomic elements
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always form groups of two they always
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pair up together you never find Just One
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of These atoms alone by itself so this
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would never just be CL it would be cl2
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instead so the equation we've got here
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is an example of an oxidation reduction
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reaction electrons are moving between
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atoms in this equation I want to
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understand how they're moving and where
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they're moving and in order to do that
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we got to write oxidation numbers for
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the different elements in this equation
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so check it out I got some information
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here that will help us write oxidation
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number for these elements we can do this
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really quick so NaCl here is an ionic
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compound sodium and chloride na is in
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group 1 a so it is always plus one okay
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CL chloride is one of the halogens here
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usually minus one positive with oxygen
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definitely minus one here and then on
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this side of the equation we have sodium
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and chlorine on their own they're
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Elements by themselves they're not
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bonded to any other elements so na over
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here is going to be zero and cl2 over
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here is going to be zero as well okay so
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those are the oxidation numbers for
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these elements now to understand how the
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electrons move we got to take a look at
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the changes in these oxidation numbers
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we'll use this information to help us
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out so let's take a look at sodium here
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na on this side of the equation it's
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plus one and then over here it's zero so
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its oxidation number goes down so that
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means that it is undergoing reduction it
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is gaining electrons so sodium is
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reduced here from + one to zero and then
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CL goes from minus1 here to zero over
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here so its oxidation number is going up
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it is undergoing oxidation and it is
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losing electrons it's being oxidized
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from minus1 to zero so sodium is reduced
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gaining electrons and chloride is
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oxidized losing electrons now there's
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something really important about this
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process and that's that this process
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doesn't happen on its own sodium
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chloride is also known as table salt and
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you could keep table salt in your
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kitchen for hundreds of years and it's
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never going to separate out into sodium
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and chlorine gas
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it's just not going to happen this
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process doesn't happen on its own by
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itself to use chemistry terms we can say
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that this process is not spontaneous
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spontaneous process is something that
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happens on its own now a big part of the
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reason why this isn't a spontaneous
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reaction is because sodium and chloride
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over here are really happy with the
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number of electrons that they have
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sodium doesn't want to gain more
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electrons and chloride here doesn't want
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to lose electrons they're totally set
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right here so we have to force this
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process to happen and that's where the
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electricity part of electrolysis comes
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into play the electrical energy from a
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battery can force this process to happen
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so here's our battery and a battery has
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these two sides the positive and
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negative the positive side of the
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battery pulls electrons in and the
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negative side of the battery pushes
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electrons out so these two things can
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force this process to happen so chloride
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doesn't want to lose its electrons but
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you know what the positive side of the
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battery just pulls electrons away from
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it right it's like you don't want to
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lose these electrons tough I'm just
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going to pull them away from you and the
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negative side of the battery that pushes
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electrons out it's going to push
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electrons to sodium sodium doesn't want
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to gain electrons too bad the negative
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side of the battery is going to push
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electrons to the sodium making this
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process happen so now I want to show you
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the device that we use to do
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electrolysis and make this process
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happen and then I want to use our Atomic
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Vision to see the atoms and electrons
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and how they move during this
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electrolysis process so here's a picture
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of the device that we use to make this
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process happen this is called an
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electrolytic cell and it's got a couple
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of different parts first we got this
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container that's full of the sodium
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chloride then we got a battery and the
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two sides of the battery are hooked up
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to what we call
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electrodes the electrodes put electrons
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into the sodium chloride and they pull
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the electrons out
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and then finally the sodium chloride
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here it's not just like the powdered
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table salt that you're used to from the
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kitchen this has got to be molten liquid
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melted sodium chloride sodium chloride
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doesn't melt until about 1500° fahr or
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800° C so it's got to be super super hot
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and this device has to withstand really
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high temperatures the sodium chloride
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has got to be molten for the
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electrolysis to happen now let's zoom in
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on this a little bit more if we could
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zoom in to the sodium chloride millions
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and millions of times this is what we'd
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see the sodium chloride is molten or
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liquid which means the sodium and the
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chloride ions have come apart from each
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other and they're in constant motion
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moving around in this container now here
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are the electrodes this is that one and
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this this is that one these electrodes
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in the diagram here are way way way
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closer together than they should be
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based on this this is definitely not to
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scale but I wanted you to be able to see
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both of the electrodes now there's
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another important part of this
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electrolytic cell and that is the
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battery the diagram that I put here
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shows the direction that electrons move
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electrons move from here into the
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battery and then out of the battery into
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this electrode so we can give names to
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these two electrodes based on how the
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electrons are moving okay the electrode
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over here we call the anode the anode is
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the site of oxidation oxidation is
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happening in here because the anode is
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pulling in electrons because this is the
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direction the electrons move now over
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here we have the cathode reduction
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happens to the cathode the cathode
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pushes out electrons because this is the
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direction that electrons are moving from
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the battery so we got the anode and the
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cathode we got the battery the
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electrodes and the sodium chloride we're
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ready to do some electrolysis I'm going
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to get rid of a few of these ions to
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make the process a little bit clearer
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okay that's a little bit clearer so now
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we hook the battery up to the electrodes
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and this is what happens so this cathode
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here is connected to the negative side
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of the battery so that means that it's
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going to have a negative charge these
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positively charged sodium atoms are
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going to be attracted to the negatively
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charged cathode because opposite charges
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attract so we got this na+ moving over
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to the negatively charged cathode and
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electrons as we said are being pushed
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out of the battery into the cathode and
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this electron is going to be given to
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the na+ ion and gaining that electron is
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going to get rid of the charge on that
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na so it's going to turn this into an
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neutral sodium atom the same thing is
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going to happen to this one over here
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it's got a positive charge it's
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attracted to the negative cathode moves
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over here an electron gets pushed from
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the battery it goes into the sodium ion
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and gaining that electron causes the
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sodium to lose it charge so now we have
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two neutrally charged sodium atoms now
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over here at the anode the opposite
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thing is going to happen electrons are
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going to be pulled out of these ions so
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we got this chloride over here it's
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attracted to the anode because the anode
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is hooked up to the positive side of the
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battery and this is negatively charged
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so it's going to be pulled over here and
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the anode is pulling in electrons so one
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of the electrons from the CL minus is
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going to be pulled up towards the
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battery and that is going to cause the
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negative charge to go away because it's
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lost one of its electrons and then over
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here this CL minus is also going to get
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attracted to the anode it's going to
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lose one of its electrons it's going to
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get pulled up here towards the battery
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and that is going to cause this to lose
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its negative charge now we said that
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chlorine here is one of the datomic
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elements so that means that we're never
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just going to find one of these atoms on
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their own as soon as they don't have a
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charge anymore they're going to pair up
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to form a cl2 molecule this is gas and
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it's actually going to float away so
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that's how the electrons move in this
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electrolytic cell here's a diagram of
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the process that I just showed you I
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want to use this to write half reactions
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for what's going on at the anode and the
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cathode so oxidation happens at the
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anode and reduction happens at the
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cathode let's write these half reactions
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so over here at the cathode we start out
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with na 1+ that gains an electron plus e
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minus the symbol for
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electron and that gives us neutral
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sodium na without a charge that's how we
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know it's neutral now over here at the
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oxidation half reaction I'm going to
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write this a little bit incorrectly
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first and then I'm going to fix it okay
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so here we start out with two cl1 minus
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okay two CL minus and then what happens
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is these lose two electrons one two get
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pulled up to the battery so I'm going to
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write minus 2 e minus that's incorrect
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but I'll fix it in a minute and that
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gives us a molecule of cl2 to gas now
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what's wrong about this well you can't
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subtract things in a chemical equation
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even though it makes a lot of sense so
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to make this correct I have to put these
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two electrons on the other side of the
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chemical equation so here is the correct
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version where I've just moved the
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electrons over here and this is the
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correct way to write the oxidation half
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reaction now that I've written the
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oxidation and reduction half reactions I
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want to show you how we can put them
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together to get a reaction for this
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whole process now let's combine these
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half reactions that we just wrote In
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order to add or combine these half
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reactions together they have to have the
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same number of electrons but they don't
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right now there's one electron here and
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two electrons here so to fix that I'm
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going to take this reduction half
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reaction and I'm just going to multiply
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it by two just like it's a math equation
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and that is going to give me this new
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reaction action I've just put a two in
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front of everything Distributing it
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across the reaction okay so there's my
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new reduction half reaction and then
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here's my oxidation half reaction now
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that they have the same number of
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electrons I can add them together and
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this is what I get I take everything on
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this side of the arrow and put it on one
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side I have my na my two electrons and
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my 2 CL on this side and then on this
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side I have my na my cl2 and my 2 e
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minus now there's still a little bit
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more that I have to do before this
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equation is totally finished if there's
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anything on both sides of the arrow we
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cancel it out so there two electrons
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here and two electrons here I'll cancel
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those out and then I have 2 na+ here and
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I have two CL minus here I can combine
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those together to make
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NA so my final equation is going to look
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like this 2 NAC and then on this side 2
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na plus cl2 and you'll notice that I've
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also put in these parentheses to show
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the physical state of each of these
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particular compounds this is liquid
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because it's so hot it's molten the na
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is also liquid because it's so hot and
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the cl2 is gas and just floats away so
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let's just pull everything together that
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we talked about here is our final
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equation for the the electrolysis of
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sodium chloride this happens because
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sodium gains electrons and is reduced
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this happens at the cathode in the
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electrolytic cell which pushes out
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electrons it's where reduction takes
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place and it's where sodium gains these
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electrons here is the half reaction for
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the reduction of
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sodium then chloride loses electrons it
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undergoes oxidation and this happens at
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the anode in the electrolytic cell the
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anode pulls in electrons oxidation
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happens there and here is the half
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reaction for chloride losing electrons
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and getting oxidized so that's how
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sodium chloride turns into sodium and
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chlorine gas during electrolysis here's
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another Super common example the
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electrolysis of water we take water H2O
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add some electrical energy and we get
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high hen and oxygen gas you might be
00:16:01
able to tell this is a balanced equation
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because I think you guys can handle it
00:16:06
now what's with H2 and O2 here well
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hydrogen and oxygen just like chlorine
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which we saw earlier are examples of the
00:16:15
datomic elements you'll never find just
00:16:18
an H or an O alone by itself these
00:16:22
elements always pair up and form twos so
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that's why we got H2 and O2 here now
00:16:30
this equation represents an oxidation
00:16:33
reduction process so electrons are
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moving they're being transferred let's
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figure out how they're being transferred
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by looking at the oxidation numbers I've
00:16:43
got some rules for writing oxidation
00:16:45
numbers here these are just a few of
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them these are just the ones that are
00:16:47
relevant to the equation that I'm
00:16:49
talking about here okay so I've got
00:16:52
hydrogen hydrogen is + one when it's
00:16:56
with non-metals like oxygen oxygen is
00:16:58
usually
00:17:01
-2 and then over here we have hydrogen
00:17:04
and oxygen these are elements by
00:17:06
themselves they're not combined with any
00:17:08
other elements so H2 is going to be zero
00:17:12
and O2 is going to be zero okay so those
00:17:14
are the oxidation numbers and now to see
00:17:17
how the electrons are being transferred
00:17:19
let's look at the change in oxidation
00:17:21
number okay starting here with hydrogen
00:17:24
hydrogen is + one and then over on this
00:17:27
side of the equation it is z Z so its
00:17:29
oxidation number is going down which
00:17:32
means that it is undergoing reduction it
00:17:35
is gaining
00:17:38
electrons Ox uh oxygen over here is
00:17:43
min-2 and then on the right side of the
00:17:45
equation it is zero so Oxygen's
00:17:49
oxidation number is going up from min-2
00:17:52
to 0 oxidation number going up that
00:17:55
means it is undergoing oxidation which
00:17:57
is loss of el electrons so oxygen is
00:18:00
being
00:18:02
oxidized it is losing electrons here
00:18:06
this process is important because just
00:18:08
like we saw in the previous example with
00:18:11
sodium chloride this process doesn't
00:18:14
happen on its own it's not spontaneous
00:18:17
you can have water in a glass for
00:18:20
hundreds of years if it doesn't
00:18:22
evaporate and it's not going to turn
00:18:25
into hydrogen gas and oxygen gas it's
00:18:27
just not going to do that on its zone so
00:18:29
just like the previous example we're
00:18:31
going to have to use the electrical
00:18:33
energy from a battery to force this
00:18:36
process to happen so now let's take a
00:18:39
look at the device that we'd use to do
00:18:41
electrolysis of water it looks a little
00:18:44
bit different than the device we talked
00:18:46
about earlier because often when we do
00:18:49
electrolysis of water we want to be able
00:18:51
to keep or hold on to the oxygen gas and
00:18:54
the hydrogen gas that get produced so
00:18:56
this is the electrolytic cell that we'd
00:18:59
use to do the electrolysis of water
00:19:02
here's what's going on we have a
00:19:04
container that has water in it and then
00:19:07
we got these weird looking things here
00:19:09
what are these well these are actually
00:19:12
test tubes that are filled with water
00:19:15
and are put upside down in the top of
00:19:18
this container so it's like you'd fill
00:19:20
them with water and then you'd very
00:19:22
carefully turn them upside down so
00:19:24
they're still filled with water and
00:19:26
they're in the container then just like
00:19:28
in the previous example we've got these
00:19:30
electrodes here the electrodes are in
00:19:34
the test tubes you can see that they're
00:19:35
like sticking in the test tubes and the
00:19:37
electrodes are hooked up to the battery
00:19:40
it's the electrodes that are putting
00:19:42
electrons into the water or pulling
00:19:44
electrons out of the water okay and then
00:19:47
finally of course we have the water now
00:19:50
I should say this electrolysis process
00:19:52
doesn't just happen in distilled pure
00:19:55
water we got to add a little something
00:19:57
like like like sulfuric acid here to
00:20:01
allow electricity to flow through the
00:20:04
water so you can't just do this in pure
00:20:06
water got to add what we call an
00:20:07
electrolyte like h2so4 sulfuric acid
00:20:12
okay now let's look at how these
00:20:14
electrodes here are connected to the
00:20:16
battery okay this electrode here is
00:20:20
hooked up to the negative side of the
00:20:22
battery so electrons as you can see here
00:20:24
are moving out of the negative side and
00:20:26
they're being pushed into this electrode
00:20:29
so that means that this is the cathode
00:20:32
it's the site of
00:20:34
reduction over here this electode is
00:20:38
hooked up to the positive side of the
00:20:39
battery so electrons are moving out of
00:20:42
it that means that oxidation is going to
00:20:46
be taking place it's going to be pulling
00:20:48
electrons from things and this is what
00:20:50
we call the anode so we've got hydrogen
00:20:54
gas and oxygen gas what gets made where
00:20:58
well well hydrogen here in water gets
00:21:01
reduced to form hydrogen gas so the
00:21:06
cathode the site of reduction is going
00:21:08
to be where hydrogen gas gets produced
00:21:12
H2 produced here at the cathode and then
00:21:16
oxygen in water gets oxidized to form
00:21:21
oxygen gas so over here at the anode the
00:21:24
site of oxidation oxygen is going to be
00:21:27
produced so we hook everything together
00:21:30
we add little sulfuric acid to the water
00:21:32
connect the electrodes to the battery
00:21:34
and we'll start seeing bubbles that's
00:21:37
the gas being formed on the electrodes
00:21:41
and those bubbles are going to start
00:21:44
moving up to the top of the test tubes
00:21:47
and if you look carefully you see a
00:21:49
really cool thing happen the level of
00:21:52
the water starts to go down because gas
00:21:57
is flowing up it's floating up and it's
00:22:00
collecting at the top of the test tubes
00:22:02
and it's forcing the water down so you
00:22:06
see the water level slowly move down as
00:22:10
the gas collects at the top of the test
00:22:15
tubes it's really cool and you can watch
00:22:16
this you can see this happen in the lab
00:22:19
now something else really interesting
00:22:21
happens you'll see what I did here and I
00:22:24
I'm not just being careless on the side
00:22:27
that's producing hydrogen
00:22:29
you get twice as much gas as the side
00:22:33
that's producing oxygen there's twice as
00:22:36
much hydrogen gas as oxygen gas why is
00:22:39
that well take a look at this balanced
00:22:42
equation here okay we have 2 H2 and just
00:22:46
1 O2 so there is a 2: one ratio of
00:22:52
hydrogen gas to oxygen gas so that means
00:22:56
that when we do this electrolysis we are
00:22:58
physically going to get twice as much
00:23:01
much hydrogen gas in this test tube as
00:23:04
we get oxygen gas over here okay so
00:23:08
that's the big picture of how we do
00:23:11
electrolysis in the lab and what's going
00:23:13
on here in the electrolytic cell now
00:23:15
let's take a look at the half reactions
00:23:18
for the reduction of hydrogen and the
00:23:20
oxidation of oxygen let's break this
00:23:22
process down into the two half reactions
00:23:25
that make it up now let me just tell you
00:23:27
when it comes to writing half reactions
00:23:29
for the electrolysis of water there are
00:23:31
so many different ways to do it and it
00:23:34
seems like every textbook or every
00:23:36
teacher has their own way of writing
00:23:38
these half reactions in this video I'm
00:23:40
using the half reactions that I think
00:23:42
make most sense but if you're teacher or
00:23:45
textbook has a way they really want you
00:23:47
to do it instead just learn their method
00:23:50
every way of writing these is
00:23:52
essentially equivalent they're
00:23:53
essentially the same they just look a
00:23:55
little bit different so again I'm using
00:23:57
the reactions that I think make most
00:23:59
sense for this video let's start with a
00:24:01
reduction of hydrogen I really want to
00:24:03
show you what's going on with the atoms
00:24:05
and electrons in these half reactions
00:24:07
okay so we start with two molecules of
00:24:11
water H2O and you'll see that I've
00:24:12
written oxidation numbers above each of
00:24:15
the atoms so in the reduction of
00:24:18
hydrogen essentially what happens is
00:24:20
it's like we take one hydrogen from each
00:24:23
of these water molecules and pull them
00:24:25
off and then we combine them to make a
00:24:29
molecule of H2 hydrogen gas now what has
00:24:33
to happen with the electrons for this to
00:24:36
take place well each of the hydrogens
00:24:39
over here has an oxidation number of
00:24:41
plus one but then they have an oxidation
00:24:44
number of zero over here so that means
00:24:47
that each of these hydrogens has to gain
00:24:50
one electron so that its oxidation
00:24:53
number can be bumped up by one okay
00:24:56
here's here's a diagram sort of showing
00:24:58
what happening here okay this hydrogen
00:25:01
was plus one and then it gains an
00:25:03
electron and becomes zero this hydrogen
00:25:06
was plus one and it gained an electron
00:25:09
and became zero where do these electrons
00:25:11
come from in the electrolytic cell well
00:25:13
they came from the cathode because the
00:25:16
cathode is what pushes out electrons the
00:25:19
cathode is where reduction happens okay
00:25:22
so we get one molecule of H2 but then we
00:25:26
have these parts of the water molecule
00:25:28
which you're just left behind so we get
00:25:30
an O and an h and these two things
00:25:33
together have a negative charge of one
00:25:35
minus these are polyatomic ions are
00:25:38
called a hydroxide ion and the reason
00:25:40
why they have a charge here is because
00:25:42
notice that their oxidation numbers
00:25:45
haven't changed because we're not adding
00:25:47
or removing electrons from the rest of
00:25:50
the water molecule so these numbers are
00:25:53
just staying the same as they were over
00:25:56
here you add these oxidation numbers up
00:25:59
and you getus oneus one so that's the
00:26:02
charge of this ion okay so this is how
00:26:06
the reduction happens with
00:26:08
pictures let's look at how we can
00:26:10
actually write an equation actual half
00:26:13
reaction for what's going on here we
00:26:15
start with two molecules of H2O then we
00:26:19
gain two electrons so plus 2 e
00:26:23
minus and that gives us one molecule of
00:26:26
H2 and then get two o
00:26:31
minus so that's the half reaction here
00:26:34
that's a half reaction for the reduction
00:26:35
of hydrogen now let's take a look at the
00:26:38
half reaction for the oxidation of
00:26:41
oxygen okay just like up here we start
00:26:45
with two molecules of
00:26:49
H2O and for the oxidation of oxygen it's
00:26:52
going to be like we pull off these two
00:26:55
oxygen
00:26:56
atoms to make a molecule of o2 oxygen
00:26:59
gas now how about the electrons in this
00:27:02
case well both of these oxygen were
00:27:05
minus two for their oxidation number
00:27:07
over here and then they became zero over
00:27:09
here so each one of them has to
00:27:14
lose two electrons to become zero this
00:27:19
one was minus two then it loses two
00:27:21
electrons become zero this one was minus
00:27:24
two it lost two electrons to bump its
00:27:26
oxidation number up it's losing
00:27:28
electrons to zero so that's what's going
00:27:32
on here now where are these electrons
00:27:36
going well the electrons are going to
00:27:40
the anode because it's the anode and
00:27:43
oxidation reduction reactions that is
00:27:46
pulling in electrons okay so this is
00:27:50
what's happening with the oxygen what
00:27:52
about the rest of this well we have four
00:27:54
hydrogens left over after we pull off
00:27:57
those oxygens and their oxidation
00:27:59
numbers are not changing because we're
00:28:01
not adding or removing electrons so
00:28:04
we're just going to get four
00:28:07
H+ over here left over that have an
00:28:10
oxidation number of plus one because
00:28:12
that's not changing let's do the same
00:28:14
thing that we did up here let's write a
00:28:17
half reaction for the process this is a
00:28:19
little bit more challenging as before
00:28:21
I'm going to write it incorrectly first
00:28:23
and then we're going to fix it okay so
00:28:24
we start with 2 H2O
00:28:28
and then we lose four electrons -2 -2 so
00:28:34
-4
00:28:36
electrons and that gives
00:28:38
us O2 +
00:28:42
4 h plus these up here now as you
00:28:46
probably know we can't use the
00:28:48
subtraction sign in a chemical equation
00:28:51
so we have to make this four electrons
00:28:55
and put it over here so this is what
00:28:57
we're going to yet instead we just move
00:29:00
this four electrons over here 4 e minus
00:29:03
there we
00:29:04
go okay there we go now we can see it
00:29:07
and these are the half reactions for the
00:29:09
reduction of hydrogen and the oxidation
00:29:12
of oxygen now let's combine them put
00:29:15
them together okay now so for combining
00:29:17
these half reactions we want them to
00:29:19
have the same number of electrons the
00:29:22
reduction half reaction that only has
00:29:23
two electrons we have four here so the
00:29:26
way we're going to solve this is we're
00:29:27
going to take this whole equation and
00:29:30
we're going to multiply it by two and
00:29:33
distributing this two across the
00:29:35
equation we are going to end up with
00:29:38
this 4 H2O four electrons 2 H2 and 4 oh
00:29:43
minus so that is our new reduction half
00:29:46
reaction now we can take these two half
00:29:50
reactions and add them together we're
00:29:52
going to get this we take everything
00:29:54
from this side of the equation and put
00:29:56
it here 4 H2O 4 4 e minus 2 H2O then we
00:30:00
have our arrow and then we have 2
00:30:03
H2 4 oh minus O2 + 4
00:30:08
h++ 4 e minus all right now there are a
00:30:13
few things that we can do here if
00:30:14
something appears on both sides of the
00:30:18
uh of the arrow here we can cancel it
00:30:19
out okay so we'll get rid of this one
00:30:21
and we'll get rid of this one but that's
00:30:23
not all we can do look at this we have
00:30:25
four o minus here and we have 4
00:30:29
H+ oh minus and H+ combine to make water
00:30:35
now also look at this we have four H2O
00:30:38
here and 2 H2O here so we can combine
00:30:42
these to get six H2O all right so here's
00:30:48
how we can rewrite it we pull these
00:30:51
together and get 6 H2O we get rid of the
00:30:53
electrons there and then we have 2 H2 we
00:30:57
combine 4 oh minus and 4 H+ to get 4 H2O
00:31:01
and then we have our oxygen but you know
00:31:04
what there's actually one more thing we
00:31:06
can do because look we have H2O on both
00:31:08
sides of the equation so I can subtract
00:31:12
it so we can get rid of it from one side
00:31:14
I'm going to do Min -4 H2O here I'm
00:31:17
going to do minus 4 H2O here that's
00:31:21
completely going to get rid of the H2O
00:31:23
on this side and it's going to leave me
00:31:25
with 6 - 4 2
00:31:28
H2O on this side here is the same
00:31:31
balanced equation that we used when we
00:31:33
started you put the half reactions
00:31:35
together and this is what you get so
00:31:37
that is the electrolysis of water
00:31:39
hydrogen is reduced it gains electrons
00:31:43
this happens at the cathode the sight of
00:31:44
reduction and H2 is produced there then
00:31:48
oxygen is oxidized it loses electrons
00:31:52
this happens at the anode the site of
00:31:54
oxidation where the oxygen is produced
00:31:57
we got these two electrodes in these
00:32:00
upside down test tubes and the gas the
00:32:03
hydrogen and oxygen collects at the top
00:32:06
and we've seen that we get twice as much
00:32:09
hydrogen gas as oxygen and that's just
00:32:11
because in our balanced chemical
00:32:13
equation there's a ratio of two
00:32:15
hydrogens to one oxygen so that is why
00:32:19
we get twice as much hydrogen here as
00:32:22
oxygen here so that's how electrolysis
00:32:25
works that's how you put electrical
00:32:27
energy into a chemical reaction to make
00:32:30
something happen that wouldn't happen
00:32:32
otherwise something like taking sodium
00:32:34
chloride and breaking it apart into
00:32:36
sodium metal and chlorine gas or
00:32:38
something like taking water and
00:32:41
splitting it apart into hydrogen gas and
00:32:43
oxygen gas
