# Tag Info

3

The main mistake is rather algebraic and forgetting the electrochemical conventions. When we write this equation, we follow the convention that all electrode potential values will be inserted right from the table with their signs intact, whether it is an oxidation or reduction. Don't change the sign of the electrode potential value. The sign of the electrode ...

3

It has been a while since I took electrochemistry so I'm not sure about the formal procedure that you're using. You wrote the correct overall reaction. $$\ce{2H3O+ + Fe -> H2 + Fe^{2+} +2H2O}\tag{1}$$ and you almost wrote the correct half cells reactions (should be $\ce{Fe^{2+}}$ in equation 3): $$reduction: \ \ \ce{2H3O+ + 2e− ->H2}\tag{2}$$ ...

2

If it may help you to understand how the Daniell cell works, you may use a language full of imagery and say that the zinc metal absolutely wants to loose its electrons, so as to go back to its initial state on Earth, that is $\ce{Zn^2+}$ like in the mineral $\ce{ZnS}$ called blende. To be allowed to carry out this transformation, $\ce{Zn}$ needs somebody or ...

2

It is a very good questions from a student who seems to be thinking deeply. I have been thinking to write on this topic for the last 7-8 years. In short the poles of the batteries are electrostatically charged and one can actually "sense" this charge with the help of sensitive electroscopes which were known in the time of Volta. The label anode or cathode ...

2

Firstly, I would replace the word "feasible" with "favorable". I'm also going to replace $E_{cell}$ with $E_{OCV}$, where the open circuit voltage (OCV) is the potential of the cell without any applied electric potential. So you're right in that if the $E_{OCV}$ is positive, the net reaction is thermodynamically favorable: it will occur spontaneously if ...

2

The primary problem is too low permeability = too high resistence of the gloves, causing high voltage drop where it should be minimal one. The gloves are not hydrophilic enough for electrolyte soaking to get low resistance. The remaining voltage - after subtracting the glove voltage drop - is not high enough to cause electrolysis by significant current. ...

1

the background limits ‘are the potentials where the cathodic and anodic currents start to flow at a working electrode when it is immersed in a solution containing only an electrolyte added to decrease the solution resistance (a supporting electrolyte). Bard's book is notoriously complex. Some bright scientists are not good at communication. Richard Feynman ...

1

In electrolysis, $Cu^{2+}$ is reduced in two steps, first to $Cu^+$ and later on to $Cu$. Of course $Cu^+$ is automatically disproportioned into $Cu$ and $Cu^{2+}$ in acidic conditions. But in neutral solutions, $Cu^+$ may react with $H_2O$, forming an unwanted red precipitate of $Cu_2O$. This will affect electroplating of copper.

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There exist two methods for teaching electrochemistry, and of course two schools of teachers. The two methods are equivalent, but they are exactly the opposite of one another. I will take an example to explain it correctly : Let us speak of the Daniell cell Zn/Cu, which uses reduction potentials equal to -$0.76$ V for Zn and +$0.34$ V for Cu, if the ions ...

1

The best reagent for detecting Cr(VI) in aqueous solution is the diphenylcarbazide, which produces a red color in presence of Cr(VI). The sensibility limit is as low as 0.2 ppm Cr(VI). This method has been developed one hundred years ago. See 1) M. A. Moulin, Dosage du chrome, Bull. Soc. chip. 31, 295 (1904). 2) H. Crossley, Diphenylcarbazide. An indicator ...

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It does not matter if the cell was previously already used in circuit or not.( unless the cell is exhausted ) For both electrodes, there is ongoing bidirectional exchange of the positive metallic cations, what changes the electrode potential. At equilibrium, both processes go by the equal rate with the equilibrium potential, given by the Nernst equation. ...

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