10
votes
Electrolysis with salt water on steel plates creates horrible black liquid
The applied current drives sodium ion to the cathode (negative pole) where hydrogen is evolved and the surrounding medium becomes more alkaline.
The more interesting - in the sense of catastrophic - ...
- 12.4k
7
votes
Accepted
Why sodium and calcium swapped their positions in electrochemistry series and metal reactivity series?
The electrochemistry series is based on the thermodynamic parameter - standard redox potential, directly linked to standard molar Gibbs energy of a formal reaction (See e.g. this libretexts doc):
\...
- 27.9k
6
votes
Why do we sometimes change the sign for standard electrode potentials?
The answer is right, but I find the double negative pretty unintuitive. The question tells you that
$$\begin{align}
\ce{2Mn^3+ + Cu &-> 2 Mn^2+ + Cu^2+} & E^\circ_\mathrm{cell} &= \pu{+...
- 65.8k
5
votes
Electrolysis with salt water on steel plates creates horrible black liquid
It is probably a mix of Fe++, Ni++ and Cr+3 oxides and hydroxides. This is a common trick by RO system salespeople to convince people how terrible their water is. They electrolyze a nail, the more ...
- 789
5
votes
Accepted
Electrolysis with salt water on steel plates creates horrible black liquid
Just count the number of electrons that you provided to the electrodes during 2 hours: 120 x 60 x 2 A=14,400 Coulomb. 1 Coulomb = 6,240,000,000,000,000,000 electrons! Do this multiplication with 14,...
- 32.7k
5
votes
Why do we sometimes change the sign for standard electrode potentials?
The standard redox/electrode potential for a half-reaction
$$\ce{ox^{m} + n e- -> red^{m-n}}$$
is defined within thermodynamics as
$$\Delta G^°_\mathrm{r}=-nFE^°_\mathrm{r}$$
for a formal reaction
$...
- 27.9k
4
votes
Why do we sometimes change the sign for standard electrode potentials?
This is how I applied what I learnt in my undergraduate freshman chemistry class to answer the given question:
In the given cell, the copper has been oxidized and the $\ce{Mn^3+}$ has been oxidized. ...
4
votes
Electrodeposition of aluminum
Aluminum can be obtained by electrolysis of $\ce{AlCl3}$ in DMSO, as shown by you in your answer, iblue. But it should be stated that
the solution should be absolutely anhydrous
once deposited on ...
- 21.2k
3
votes
Electrolysis when E_cell = 0
You are confused because you are mixing two different concepts. Half-cells belong to the field of potentiometry when no electric current is passing through the circuit. So that calculations you do ...
- 32.7k
2
votes
Accepted
Electrodeposition of aluminum
So, time went by and I got a little wiser. Answering my own question in the hopes that it may be useful to someone, somewhere, sometime.
The issue is that aluminum has an electrode potential way ...
- 181
1
vote
Why do we define molar conductivity?
Molar conductivity reflects ion or ionic compound behaviour, while conductivity reflects rather their concentration. For high dilution, the former is nearly constant, the latter nearly proportional to ...
- 27.9k
1
vote
Where is the LITHIUM in NMC Cathode?
(Reusing my deleted comments:)
$\ce{Ni + Mn + Co}$ do not make 100%, as they are there in form of mixed oxide. Each 33% rather means they are in 1:1:1 ratio. E.g. for purely $\ce{Co}$ cathodes, the ...
- 27.9k
1
vote
What endothermic reactions can be effectively reversed by electrolysis?
Any elemental, i.e. single step, reaction and many more complicated reactions that can reach equilibrium, can be reversed. The forward and reverse reactions in an equilibrium situation follow the same ...
- 789
1
vote
Electrolysis with salt water on steel plates creates horrible black liquid
Warning! In the process of this experiment, you most possibly have created some amount of toxic, carcinogenic, and environmentally harmful waste. Read further for answer to your question and more ...
- 11
1
vote
What starts the reaction in a voltaic cell?
I think your iterpretation of electrochemical cell is incorrect.
Firstly, the electrode is not dipped
in a neutral electrolyte. You must have seen that whenever an electrolyte is represented for an ...
- 11
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