Galvanic Cells

[@mohammadfattal9303]

A tip for you guys , if your finding it hard knowing whether the anode or cathode is reduction or oxidation , just look at the fifth letter of either reduction or oxidation. reduCtion- it starts with C so its definitely cathode oxidAtion- with A so Anode so oxidation happens at anode and reduction at cathode

[@jelloreyes1]

or that anode and oxidation both begin with vowels

[@varun009]

Angelo Reyes I like his way better even though I've been wired to automatically know which is which.

[@israelsornoza1769]

Or you could just think of which letter comes first... Anode, Oxidation, Negative terminal Cathode, Reduction, Positive terminal

[@pretzelover]

Israel Sornoza Beautiful, thank you

[@sachitechless]

I've been taught Cathode / Reduction, Consonants, Andoe / Oxidization, Vowels.

[@blizzrd6578]

I could not, for the life of me, picture in my head what the salt bridge was actually doing. Thanks to you, I now can and have a much better understanding of the galvanic cell! Thank you.

[@propnash]

browsing YOU TUBE for last 5 hours , finally you are the only one who explained from elementary level.. thank you

[@waterfoker8558]

i've searched all over for a good explanation of what happens to the ions as they build up and what's the purpose of the salt bridge and this video is the only one that explains it near the end of the vid... thanks

[@amershloul2247]

Skip to 9 :01 for galvanic cell :)

[@jschlatt]

amer shloul youre doing the lord's work son

[@young-igotana-jamie5316]

God bless you,iyou made it look so simple and informative!

[@yashgupta9316]

Easy way to remember what happens(oxidation or reduction) at cathode or anode:Just remember ANode OXidation (an ox) and REDuction CAThode(red cat).

[@tamagonyan]

Thanks for the tutorial! I finally understand what's happening with batteries and how the potentials for each half reaction are applied.

[@JamesLactao]

Thanks a lot for this. I'm currently teaching General Chemistry and your explanation is a good refresher for me, having not taught Chem in a long while.

[@matheusbarbosa2575]

Dude, I'm in engineering chemistry right now and the professor sucks at lecturing. I can literally skip a week of lecture and do watch these 20 minute videos. Thank you soooooo much!

[@oliverhug3]

Wish I had a teacher like that in the past

[@dopexox]

What I love about chemistry is that it is so relative to real life situations like in this video Khan was talking about the positive ions wanting to stay and the negative ions wanting to leave and that's I make sense chemistry by implicating it to life

[@sigmabond1289]

dis s by far d best video ive seen....so very happy!!! thnx a lot!

[@Djlawson1000]

I'm straight up boned for tomorrows test... pray for me fellow students.

[@JonnyBravoZero]

+Djlawson1000 howd it go?

[@MaartenvanRossemLezingen]

+Djlawson1000 Yeah how did it go?

[@Djlawson1000]

C on this exam, but passed my AP exam. I truly am blessed!

[@Djlawson1000]

Well I received credit for the course, so I'll take it.

[@MaartenvanRossemLezingen]

Oh man I'm so glad I'm done with high school and chemistry now :P

[@beingstudious9300]

Sir...."your small little note that doesn't make a big difference" was actually very interesting......😀😁thank you😄

[@reaalex]

The way you explain the concepts completely engages me to love science, keep up the great work :)

[@cheblichebli8237]

Man my teacher sucks at teaching chemistry thanks to you I understood this.Appreciate it

[@edrismoradi5739]

I really like your explanation! Great job. thank you

[@zacharyivanhawkins251]

The "voltages" that Sal is speaking of (known values) are known as standard REDUCTION potentials. +0.76v, as Sal suggests, is the standard oxidation potential of Zn(s) --> Zn^2+(aq). I think the best thing to learn is that E(cell) = E(cathode) - E(anode), and that the half-reaction with the highest standard REDUCTION potential will occur at the anode. So...E(cell) = (+0.34V) - ( -0.76v) = 1.1v for this reaction. I'm pretty sure most tables listing electrical potentials will list the reduction potential, so E(cathode) and E(anode) are both Stand.Reduction potentials found in those tables.

[@khanacademy]

You are correct. Even though the electrons flow from the anode to the cathode, the convention is to say that "current" is flowing from the cathode to the anode. Maybe I'll make another short video to clear this up.

[@ull893]

Khan Saab, all i wanted is an explanation for the salt bridge..it was hard to understand the salt bridge part. I looked all the videos available,,,all of them said, " Salt bridge is used to maintain the electrically neutrality of the solution" now what did that mean that to me..a Big BS..You are the only one to explain the salt bridge properly...Great job Sir..and congrats on you being nominated for the google award..!!

[@maxpayne5257]

Thank you! your explanation is much better and clear than my shitty copy and paste book

[@bennylincon6033]

Incredibly helpful, keep up the good work

[@JacobLJacques]

This is ridiculously helpful i have an exam tomorrow ans had to know this concept

[@MikalaRamos]

This clarifies everything!!!

[@DrZale]

Good explanation / diagrams, I was able to grasp these concepts even though its been a few years since my gen ed chemistry course ;)

[@audreykaoisthebest11]

ive learned more from this 18 minute video than i have from my chemistry teacher all semester

[@mhehar3yahoo]

The current on the anode is considered a positive current according to international convention. However, anode is considered positive in an electrolytic cell and negative in galvanic cell. While, cathode is the opposite.

[@Oelov]

the day that this video was released... my favorite date of the year!

[@eyadsaleh12]

unbelievable explanation thanks

[@BoredEnoughToDie]

Thank you so much. This is one of the possible questions in the redox reactions chapter in my 11th grade exams and I really want to score good.

[@brodiearbuckle]

movement of ions from the salt bridge compensate for the increasingly positive charge on the left hand side (anode) and increasingly negative charge on the rhs (cathode). say the salt bridge was pot. nitrate KNO3 then the increases in "positiveness" in left hand side is compensated for by an influx of NO3- nitrate ions, from the salt bridge. similarly the increasing positiveness is compensated for by K+ ions.

[@RImAPhan]

You're amazing! You answered all the questions I was thinking of during studying this chapter without me even asking. :)

[@brandonjgallegos]

the cathode is the positive electrode (terminal). Electrons flow from anode to cathode in a galvanic cell. sooo electrons flow from the negative electrode to the positive electrode because they are attracted to the positively charged cathode. the top comment shows a great mnemonic for this. about 13:00 in the video explains this pretty well

[@KoreaxxLove]

@AmirTunes Well, this reply is really late, but for anyone who is wondering...It occurs spontaneously due to a potential energy difference. The potential energy of electrons is higher in the anode than in the cathode, so electrons flow spontaneously from the anode to the cathode.

[@NJKjonasfan4ever]

where did you do your studies? high school, university, etc must be real good schools cause your teaching is so good!

[@TheLegendaryNinufa]

2 years. 2 bloody years I've been writing exams on this and only now, in less than 18 minutes, you've managed to explain it in a way where I actually know wtf is going on.

[@mle225]

@Villacis80 Actually it is. Just because it only has one charge doesn't mean it isn't a transition metal.

[@B3rNd92]

great :) im german but your way of explaining is that good that its easier for me to watch your version in english than the teacher's in german

[@salut295]

My essay is going to be a peace of cake, thanks to you!

[@GenericCoder]

@AmirTunes Its because electronegativity which is the measure of how much atom want to attract electron. The Zinc electron would tend to jump to the Cu.

[@Francesco_Armillotta]

Wonderful explanation :)

[@TravelWithTea8]

So the electons will never be in the liquid solution?

[@mcbaq]

the convention is that in the equations the electrons are always placed on the left side of the equilibrium and so this would mean the E value of it is -0.76, also because the equation for the standard cell potential is..........E(cell)=E(positive terminal) - E(negative terminal)...... the answer would be.............. 0.34-(-0.76)=0.34+0.76= 1.1V

[@ExitPro]

You explain everything so simple and awesome compared to the books that tries to pull the whole marathon run, just over something as simple as this

[@lillymitton7181]

Anode and Oxidation both start with vowels, Cathode and Reduction both start with consonants

[@smartaleck05]

Cathode (on the right); it's the electrode that gains electrons, so yes.

[@thehelifreak]

Awesome video . Thanks a lot

[@MCWon212]

Thanks man! I have to make a 97 to make an A in my chem class tomorrow. I have a feeling that I will make it happen!

[@amm23ka]

Thankyou SO much. This is amazing.

[@sinekonata]

Does the KCl in the salt bridge so willing to separate into ions that it does it almost for free? Or does the ionisation or at least the movement of ions towards their preferred solutions bear some cost in the total energy produced by the battery?

[@aznbryanc]

Thanks so much for this. Helped me out big time!

[@hellokittydimaggio]

@AmirTunes b/c on the activity series table, zinc is more higher on the table than copper, which means its more easily oxidized (go from Zn to Zn2+), if it were the other way around and copper was the solid, I don't think the reaction would take place bu im not sure...

[@Blueknightex]

By the way an ionic bond is between a metal and a non-metal.(two 'single' elements). SO4 2- is not a non- metal it is a "molecule"(made up of elements sulfur and oxygen). So when Cu 2+ is bonded to it they form a "molecule".

[@ELLo1997]

@AmirTunes because Copper is more noble ten Zinc. The non-noble metal is always getting oxidiced (Zn --> Zn+² + 2e-) and the noble one wants to get reduced into his elemental state (Cu+² --> Cu + 2e-). i hope that helped..

[@xinrui9181]

love all your videos! wish u r my professor!!! =)

[@proffezur]

Wow... The US is very behind. I learned this in grade 12, and learned even more advanced concepts dealing with electro chemistry... But hey what can you do, this is but one reason why CANADA PWNS ALL!!!

[@shouryap]

Oh yeah! That is correct. If the device produces power, then the cathode is positive and the anode is negative.

[@hpx4060]

What I got out of this: If the copper can get some, it will get hard, making the zinc wet

[@andrewp303]

lol thats what i use, i love how out of all the fancy and logical sounding methods like 'oilrig' and 'leo the red cat' i remember "gerc"

[@AcrobaticlCow]

this stuff is really helpful, thanks

[@poojamehta8498]

Ty...ur videos r vry helpful

[@asiunia1982]

You are a god! Thanks man!

[@7Supernova7]

hello, interesting videos, wich job would have to do with these kind of things,, cells, electricity through chemical reactions ? cant decide what job

[@siulreynoso7271]

Good vid. Helped a lot.

[@cnfused100]

@AmirTunes nd @povern7 its bcz the E value of Cu is less positive than Zn thus making it easier to reduce hope it helps :)

[@RedEnergySounds]

Thank you man. Needless to say that your voice is JUST like charlie the unicorn

[@tre-moon-dous6122]

i bet everytime he makes a video for a chemistry problem, he didnt even do any revision, he just went with it..

[@pianoman1928]

Great video! A quick question if anybody can answer. So is the life of the battery or galvanic cell, than, limited by the amount of this "pseudo-solution" in the salt bridge? I would imagine that at some point, the # of ions of the of the salt bridge would be exhausted and this the reaction would cease.

[@topilopi123]

Great vid!

[@TypescriptErrorsCentral-hg7hv]

I really wonder how long the process of flowing electrons from anode to cathode will continue? I assume that the electrons of Zn might end or finish at some point and it would not be like infinite electron production. If that is the case how long this process will take???

[@leongckl4773]

Does it matter what kind of solution the zinc and copper are dipped into? and what kind of compound the salt bridge is made up of?

[@ukidding]

what is the oxidising agent?...is it chlorine ion ( from the salt bridge)? what is the reducing agent ?

[@MrBlash93]

Thank you for your video

[@DrMisaSam]

This guy has a really cool voice.

[@HarshPrriyaOfficial]

Is a cathode positive or negative? I think cathode is negative because It attracts cations, which are positively charged.

[@annekatownsend6784]

To Khan Academy, or anyone who knows how to answer this Q, In a Galvanic Cell, a Voltmeter is connected across the two half cells and it has a very high resistance. But this would inhibit the flow of current between the two half cells, therefore where would the ions that want to jump out of the solution and form solid atoms get their electrons from ??

[@medwatt]

Correction : Conventional current flows in the opposite direction of electrons. Hence at 12:27, the current arrow should have been reversed. Please note !!

[@kylesimon1715]

During the half reaction for Zn, shouldn't it keep its +2 Charge on the product side of the reaction? It just wasn't written and I have been doing it that way this whole time; or does it not make a difference?

[@Keatz09]

Well, the test tomorrow is going to kill me.

[@johndoe-bq1xt]

A cathode is the negative terminal and an anode is a positive terminal.

[@digiconvalley]

i couldnt understand the positive and negative terminal thing. cathode is the negative electrode, isnt it?

[@allanahgirl]

I looooove your videos! I just can't wrap my mind around the fact that Zn has a reduction potential of 0.76V and Cu has 0.34V. I thought the higher the reduction potential, the more willing it will be gain electrons not give away electrons. could you please explain this? btw, you're awesome!

[@gamefaq]

tiny errors. but i still enjoyed the entire video. keep it up! at around 5:30, you left the 2+ charge off the Zn on the right side of the half reaction. at around 12:30, you said that a current was flowing but you drew an arrow going to the right. maybe you should have said that its the electrons that are flowing to the right since current flows to the left in your galvanic cell.

[@juni172]

thank you so much

[@h0nk3yt0nk]

phenomenal

[@beautifulquranrecitationle631]

My concern is that for Zn they're giving the value as a negative and Cu as a positive is the same as you have just explained like how badly the electrons wanna move

[@shouryap]

Cathode is positive? Anode is negative?

[@dellnegerpaul]

There is a misstake: the negative Anion goes to the positiv anode, positive Kation to negative katode

[@stucrampton]

zn actually has a reduction potential of -0.76V so you were right

[@FDSeeker111]

ANOX (anode is oxidation) REDCAT (reduction @ cathode) and OILRIG (Oxidation Is Loss of electrons, Reduction Is Gain of electrons)

[@Adben65]

a good mnemonic is OILRIG Oxidation Is Loss Reduction Is Gain

[@samerapornpan8423]

So, becuase it has a higher standard potential then Zn, Cu oxidizes which makes it a place where the reduction occurs and therefore is a cathode. But Zn, on the other hand, is place where the oxidation occurs; it reduces Cu, and hence an anode.......or what? And I'd like to ask how the standard potential in this paticular case is measured. I just know how one would caculate the electric potential between 2 ponit charges with one of them being fixed; intergral of work done to move the other charge from infinity to a place where distant beteewn them is r, but right now I just can't see the relationship between them or if there's a connection at all.

[@irmb5teS]

thats great, i was wondering, have you done electrolysis?

[@KobePlayz]

good video though,but how did you get the .34v in half reaction?,and .76v in the other reaction?.

[@atong518]

thank you for the help :)

[@MrFeatherTouch]

in the part where the zinc and copper bars are in solution why are there already copper ions in the solution? is it the same as why there are zinc ions in its respective solution? Because of the dissociating power of water? As in; water strips ions from both bars creating soltuions with metal ions?

[@sochillification]

OIL RIG Oxidation is loss...Reduction is gain (of electrons)

[@smashadams9811]

Yeah, current is in the opposite direction of electron flow.

[@GreatVgnc]

That was a very good video, but I would suggest going more over spontaneous reactions, as in the Zn redox. reaction

[@LordSorontur]

Dear Sir As a school project I built a very simple lead-acid battery to investigate cycle fade. The capacity of my lead-acid battery decreased as the number of cycles increased, as expected. Surprisingly enough, the capacity increased after a 24 day period of deep discharge. I did the same thing three more times (so a couple of cycles followed by a long period of deep discharge) and every time the capacity had increased after the period of deep discharge. The battery did become more difficult to charge (to induce current flow a voltage of about 10 to 16 volts was necessary, just for a few seconds) and eventually it stopped working. However, I was very surprised to see that the capacity loss after a few cycles, and I was wondering whether you could enlighten me. I assume you will not have time to answer my question, but I'd greatly appreciate if you could shed some light on this issue. I have attached my results to this email, in case you are willing to take a look. Thanks in advance, Nol Duindam