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.
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
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
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!
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.
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
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.
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.
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..!!
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.
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
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.
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.
@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.
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!!!
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
@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...
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.
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!
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
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?
@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.
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???
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 ??
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".
@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..
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.
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.
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
I've watched all the previous videos and have to say this one confused me quite a bit. Could you do a more in depth video explaining the "why's" there seems to be so much assumptions made without any basis.
really nice vid. if anybody's looking for a really nice overview of galvanic cells, i stumbled across a video on some guy's channel called J Co Review... it's short, sweet, and taught me in 5 mins what my prof failed to teach me in 45 lol
![โอ้เธอช่าง... - บี้เดอะสกา ft. ต๋อง เทวัญ (Prod. by ป๋าเพชร) [Official MV]](http://i.ytimg.com/vi/zbWhiLFmVL0/mqdefault.jpg)
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.
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
or that anode and oxidation both begin with vowels
Angelo Reyes I like his way better even though I've been wired to automatically know which is which.
Or you could just think of which letter comes first...
Anode, Oxidation, Negative terminal
Cathode, Reduction, Positive terminal
Israel Sornoza Beautiful, thank you
I've been taught Cathode / Reduction, Consonants, Andoe / Oxidization, Vowels.
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
browsing YOU TUBE for last 5 hours , finally you are the only one who explained from elementary level.. thank you
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!
Wish I had a teacher like that in the past
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.
God bless you,iyou made it look so simple and informative!
dis s by far d best video ive seen....so very happy!!! thnx a lot!
Sir...."your small little note that doesn't make a big difference" was actually very interesting......😀😁thank you😄
Man my teacher sucks at teaching chemistry thanks to you I understood this.Appreciate it
Thanks for the tutorial! I finally understand what's happening with batteries and how the potentials for each half reaction are applied.
The way you explain the concepts completely engages me to love science, keep up the great work :)
Easy way to remember what happens(oxidation or reduction) at cathode or anode:Just remember ANode OXidation (an ox) and REDuction CAThode(red cat).
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
Skip to 9 :01 for galvanic cell :)
amer shloul youre doing the lord's work son
Incredibly helpful, keep up the good work
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.
I really like your explanation!
Great job. thank you
I'm straight up boned for tomorrows test... pray for me fellow students.
+Djlawson1000 howd it go?
+Djlawson1000 Yeah how did it go?
C on this exam, but passed my AP exam. I truly am blessed!
Well I received credit for the course, so I'll take it.
Oh man I'm so glad I'm done with high school and chemistry now :P
Thank you! your explanation is much better and clear than my shitty copy and paste book
ive learned more from this 18 minute video than i have from my chemistry teacher all semester
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.
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..!!
This clarifies everything!!!
You're amazing! You answered all the questions I was thinking of during studying this chapter without me even asking. :)
This is ridiculously helpful i have an exam tomorrow ans had to know this concept
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
the day that this video was released... my favorite date of the year!
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.
Good explanation / diagrams, I was able to grasp these concepts even though its been a few years since my gen ed chemistry course ;)
Thankyou SO much.
This is amazing.
unbelievable explanation
thanks
Thanks so much for this. Helped me out big time!
Awesome video . Thanks a lot
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.
Wonderful explanation :)
My essay is going to be a peace of cake, thanks to you!
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
this stuff is really helpful, thanks
where did you do your studies?
high school, university, etc
must be real good schools cause your teaching is so good!
You are a god! Thanks man!
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
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!
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.
Good vid. Helped a lot.
Ty...ur videos r vry helpful
love all your videos! wish u r my professor!!! =)
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.
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"
Thank you for your video
@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.
Thank you man. Needless to say that your voice is JUST like charlie the unicorn
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!!!
Great vid!
thank you for the help :)
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
Cathode (on the right); it's the electrode that gains electrons, so yes.
Oh yeah! That is correct. If the device produces power, then the cathode is positive and the anode is negative.
Anode and Oxidation both start with vowels, Cathode and Reduction both start with consonants
i bet everytime he makes a video for a chemistry problem, he didnt even do any revision, he just went with it..
So the electons will never be in the liquid solution?
Thank u really helpful !!
@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...
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.
thank you so much
This guy has a really cool voice.
What I got out of this:
If the copper can get some, it will get hard, making the zinc wet
@Villacis80 Actually it is. Just because it only has one charge doesn't mean it isn't a transition metal.
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!
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
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?
@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.
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???
phenomenal
Well, the test tomorrow is going to kill me.
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 ??
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".
thank you!
@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..
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.
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.
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
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?
I've watched all the previous videos and have to say this one confused me quite a bit. Could you do a more in depth video explaining the "why's" there seems to be so much assumptions made without any basis.
thats great, i was wondering, have you done electrolysis?
khan academy saves my life once again.
Thanks so much!!!
A cathode is the negative terminal and an anode is a positive terminal.
really nice vid. if anybody's looking for a really nice overview of galvanic cells, i stumbled across a video on some guy's channel called J Co Review... it's short, sweet, and taught me in 5 mins what my prof failed to teach me in 45 lol
There is a misstake: the negative Anion goes to the positiv anode, positive Kation to negative katode
Is a cathode positive or negative?
I think cathode is negative because It attracts cations, which are positively charged.
thank you sal
13:35 "zinc zumping off" made me lol :p...everything seems funny when you're trying to cram every bit of a 2 year ib chem course in one night -__-
zn actually has a reduction potential of -0.76V so you were right
Oh my god he knew what I was going to say!
@AmirTunes nd @povern7 its bcz the E value of Cu is less positive than Zn thus making it easier to reduce hope it helps :)
Thank you
lol everyone's waiting until a test is coming to watch these kinds of videos meanwhile my teacher actually tells me to
Chem makes me cry
That was a very good video, but I would suggest going more over spontaneous reactions, as in the Zn redox. reaction