Questions tagged [electrochemistry]

The branch of chemistry that deals with the study of redox reactions and how they can be applied to generate electricity (in electrochemical cells) and to carry out non-spontaneous reactions using electricity (electrolysis).

Filter by
Sorted by
Tagged with
6
votes
1answer
5k views

If the ferric ion is more stable than the ferrous ion, then why is it readily reduced to the latter?

The standard reduction potential value for the Ferric ion: \begin{align} \ce{Fe^3+ + e- &<=> Fe^2+} & E^\circ &= 0.77 \end{align} The value is positive, hence it means that ferric ...
6
votes
1answer
280 views

AgI and AgCl reduction potentials

The reduction potential for $\ce{AgI}$ is $-0.15\ \mathrm{V}$ and for $\ce{AgCl}$ it’s $0.22\ \mathrm{V}$. As $nFE =-\Delta{G} = T\Delta{S} - \Delta{H}$ this must imply that $\ce{AgI}$ is a stronger ...
6
votes
1answer
1k views

Why soak filter paper in K2SO4?

From a description of my experiment: Potassium iodide crystals are place in the middle of filter paper soaked with potassium sulphate and phenolphthalein. Two electrodes are placed on the filter on ...
6
votes
1answer
997 views

Does water vapor in the air oxidize copper?

My friend is installing copper pipes in his house, which is going to be in a humid area, and he says that copper will only be oxidized by the air and the excess water vapor in the humid air won't ...
6
votes
1answer
17k views

Why is the water reduction of oxygen favored in acidic conditions?

The standard reduction potential of diatomic oxygen in acidic conditions is +1.23 volts. However, the standard reduction potential of diatomic oxygen in basic conditions is only +0.40 volts. Why is ...
6
votes
2answers
271 views

Will a film of oil on water retard evaporation (of water) and prevent air and atmospheric impurities from diffusing into it?

I vaguely recall hearing that a layer of oil on water will slow down the evaporation of water, as well as serving as a barrier that would prevent (or retard) the diffusion of air and atmospheric ...
6
votes
1answer
774 views

Does conductivity change in a solution due to rust?

I plan on conducting an experiment in which I place an iron nail in water and analyze its rate of corrosion into rust with different concentrations of NaCl. My original plan was to cover the water in ...
6
votes
1answer
336 views

How are the chemical reactions of the table of standard reduction potentials experimentally determined?

My background: I've read several books and articles on electrochemistry and even do photoelectrochemical research in a lab, so I'm somewhat familiar with the concepts and techniques. In texts on ...
6
votes
1answer
931 views

Corrosion of a galvanic couple made with silver and gold

If a bangle is made out of gold and silver, connected with each-other would there be corrosion happening? If so, can it be explained using the galvanic series? Also do those metals undergo oxidation ...
6
votes
1answer
177 views

galvanic corrosion in the wild: where is the reduction?

Galvanic corrosion occurs of an active metal (i.e. iron or zinc) in contact with a passive metal (i.e. copper) in a conductive solution. A famous example is the corrosion of iron girders in contact ...
6
votes
3answers
5k views

What can be used as an electrolyte in water to perform electrolysis other than salt?

I am looking for an electrolyte to use in water to perform electrolysis. It can't be salt, as salt ($\ce{NaCl}$) would cause the chemical reaction of $$\ce{2H2O + 2NaCl -> Cl2 + H2 + 2NaOH}$$ or ...
6
votes
1answer
34k views

What determines the strength of reducing and oxidizing agents?

The best reducing agents are located at the bottom left of the periodic table (low electronegativity) and the best oxidizing agents are located at the top right of the periodic table (high ...
6
votes
2answers
6k views

What current and voltage are best for electrolysis rust removal?

I weld carbon steels all the time, and sometimes I get parts from the scrapyard. Unfortunately, these parts are generally oxidized, so I've been assembling an electrolysis tank for it. This tank ...
6
votes
2answers
979 views

Nernst equation and electrolysis

Let's say we have a stable solution of $\mathrm{A}_{\left(\mathrm{aq}\right)}^{2+}$ and $\mathrm{C}_{\left(\mathrm{aq}\right)}^{+}$ , with their respective counter-ions. The associated redox ...
6
votes
2answers
4k views

What is the role of hydrochloric acid in a copper electroplating bath?

Considering water as a given, the third most important ingredient in a copper electroplating solution, as a short survey of related recipe webpages will show you, is hydrochloric acid (HCl). Here's a ...
5
votes
5answers
2k views

Electrolysis of Water

What is the mechanism for the electrolysis of water? I understand that hydrogen and oxygen gas are made, but how exactly does this happen when electrons are passed through water? A diagram would be ...
5
votes
1answer
2k views

Delta G for Standard Hydrogen Electrode reaction

I’m dealing with electrochemistry problems. For the following reaction $$\ce{2H+ +2e- <=>H2}\quad E^\circ=0\ \mathrm{V}$$ Does it make sense to say $$\Delta G^\circ=-nFE^\circ=0$$ Which would ...
5
votes
1answer
13k views

How to find the band gap for a compound?

I have processed a si/polymer hybrid using a silane coupling agent which I need to determine the energy gap / band gap. Would you please let me know the procedure to go about determining the band gap?...
5
votes
1answer
2k views

How can I produce hydrogen gas efficiently and cheaply?

I have been intrigued by one of the principles of chemistry lately- electrolysis. In my knowledge, electrolysis is a quite dangerous operation as the decomposition of water produces hydrogen and ...
5
votes
2answers
11k views

Correct equation for Ionic Conductivity (λ) in Solutions?

We haven't started on Electrochemistry at school yet, but I did manage to find some time to read up on the topic. One thing I've noticed from when I started, is that different books and sites use ...
5
votes
3answers
15k views

What is the difference between molar conductance and molar conductivity?

I'm learning (or at least trying to learn) about electrochemistry, but a major obstacle to that, is that different books I refer use different terms for the same symbols. So in a last ditch attempt to ...
5
votes
3answers
35k views

Why is the reaction between potassium permanganate and hydrogen peroxide spontaneous?

When hydrogen peroxide is mixed with potassium permanganate, oxygen gas and water vapour are formed, according to the reaction (source): $$\ce{2MnO4- + 3H2O2 -> 2MnO2 + 2H2O + 3O2 + 2OH-}$$ This ...
5
votes
2answers
5k views

Why do electrons follow from Zn to Cu but not Cu to Zn in the lemon battery experiment?

In the lemon battery experiment, as I understand, both $\ce{Zn}$ and $\ce{Cu}$ meet acid in the lemon, cause $\ce{Zn}$ and $\ce{Cu}$ release electrons to form $\ce{Zn^{2+}}$ and $\ce{Cu^{2+}}$. So ...
5
votes
1answer
287 views

Will nitrate be able to oxidise mercury?

We have the following data: \begin{align} \ce{NO3- + 3 e- &-> NO} &\quad E^\circ_1 &= \pu{0.96 V}\\ \ce{Hg^2+ + 2 e- &-> Hg} &\quad E^\circ_2 &= \pu{0.86 V} \end{align} ...
5
votes
1answer
407 views

Is a strontium-fluorine battery the highest voltage battery using pure elements?

Strontium has a very low standard electrode potential and fluorine has a very high one. $$ E_{\ce{F2 + 2e^- -> 2F^-}} = 2.87\mathrm{V} $$ $$ E_{\ce{Sr -> Sr^+ + e^-}} = -4.10\mathrm{V} $$ In ...
5
votes
2answers
3k views

How to determine the potential of a cadmium zinc cell under standard conditions?

I write the half-equations: \begin{align} \ce{Zn &<=> Zn^2+ + 2e^-}& E^\circ &= +0.763~\pu{V}\\ \ce{Cd^2+ + 2e- &<=> Cd}& E^\circ &= +0.403~\pu{V} \end{align} In ...
5
votes
2answers
519 views

Lemon Battery works on water?

My son and I were using a mini science experiment kit for creating batteries with copper, zinc, and lemonade, similar to the famous lemon battery project. My son's hypothesis was that the liquid had ...
5
votes
1answer
478 views

The spontaneity of a redox reaction

Suppose we have a redox reaction and we want to see in what direction the reaction is spontaneous. We do this by comparing the standard reduction potentials of the sub-reactions available in the main ...
5
votes
1answer
158 views

Will oxidation/reduction of copper still occur in an electrochemical cell if it is not in an aqueous environment?

Notation of the reduction and oxidation of copper typically includes the aqueous state. Illustrated below: $$\ce{Cu(s) -> Cu^2+(aq) + 2e-}$$ This event usually occurs at 0.34 V. What if the copper ...
5
votes
1answer
2k views

Galvanic cell involving a hydrogen electrode and copper electrode in sodium hydroxide

A galvanic cell consists of a standard hydrogen electrode and a copper electrode. Suppose that the copper electrode is immersed in a solution that is $0.100\ \mathrm{M}$ in $\ce{NaOH}$ and that ...
5
votes
2answers
501 views

Formation of species in electrolysis

I understand the principles of electrolysis of salts in aqueous solutions, but there are two points on which i am unsure. At the positive electrode, how can you work out which ions will ...
5
votes
1answer
134 views

Why can some redox half-reactions be combined and some cannot? [duplicate]

I mean by "combining" is to make a new half-reaction equation and not an overall equation for a reaction in whole. For instance, I was trying to arrive at the following half-reaction: $\ce{MnO2(s) + ...
5
votes
1answer
847 views

In a galvanic cell, why does an electrode with a higher potential “pull” the electrons from the electrode with a lower potential?

I'm doing Grade 12 Chemistry and I'm unsure of this, taking the hydrogen electorde as having a potential of 0 volts. I'll use the copper-zinc cell as an example. Just let me know if I've got the full ...
5
votes
3answers
10k views

Express the maximum work from a voltaic cell

The net cell reaction of an electrochemical cell and its standard potential is given below: $$\ce{ Mg + 2Ag+ ->Mg^{2+} + 2Ag} \ \ \ \ \ \ \ \ E^\circ=3.17\:\mathrm{V}$$ The question is to find the ...
5
votes
2answers
293 views

Decreasing magnitude of peaks in cyclic voltammogram?

I'm in an instrumentation course and we covered cyclic voltammetry earlier in the semester and will be doing an experiment in CV next week. My question is this: If you have a reaction and sweep the ...
5
votes
1answer
2k views

Would an amalgam filling under or next to a gold crown cause any electrochemical reaction?

Would a mercury amalgam filling deteriorate faster if it was in contact with a gold crown?
5
votes
3answers
1k views

Why does a complete discharge destroy a Li-Ion-Battery?

I read that completely discharging a Lithium Ion Battery is a very bad idea because it will lose plenty of capacity. But why? I know that the reaction (fot the LiFePO4 battery) is: $$ \ce{LiFePO4 + ...
5
votes
1answer
9k views

How would using different salts in a salt bridge effect the voltage generated by a voltaic cell?

If I use a range of different nitrate solutions (e.g. calcium nitrate, iron nitrate) for the salt bridge in a voltaic cell, what effect would it have on the flow of ions in the voltaic cells? Will ...
5
votes
2answers
145 views

In a simple chemical cell

Why do the electrons, arising from the oxidation of the anode, flow through an external circuit? Why does it not just flow through the electrolyte and reduce the cathode? Why do the electrons give the ...
5
votes
2answers
3k views

Standard hydrogen electrode, why hydrogen?

Why is the hydrogen electrode used as the reference to set electrode potentials? Could any other element be used instead?
5
votes
1answer
695 views

Iodometric titration of copper – standard electrode potentials

Upon inspection of the standard electrode potentials for the half reactions for both $\ce{Cu^2+}$/$\ce{Cu+}$ and $\ce{I2}$/$\ce{2I-}$, it becomes apparent it should be the iodide ions that act as the ...
5
votes
1answer
558 views

how to measure dissolved oxygen?

How do you measure dissolved oxygen reliably in a culture of cells? This page has info on one sensor: http://water.me.vccs.edu/concepts/domeasure.html how would you know that this sensor is working - ...
5
votes
1answer
2k views

How to calculate the potential via Hess's law? Is my textbook wrong about this?

It is my understanding that to apply Hess' Law to this equation the top equation sign would be reversed and the outcome would be +0.65 V. Often the system produces incorrect answers. I was looking ...
5
votes
2answers
1k views

Side products during the electrolysis of Copper Sulfate?

Using good quality reagents, during the electrolysis of $\ce{CuSO4}$ (at $\mathrm{15V ~ \& ~ 2A}$), I have noticed a significant amount of Hydrogen generated at the negative electrode in addition ...
5
votes
2answers
863 views

Unknown white precipitate in electrolysis of water

I was electrolysing water using a copper anode and zinc cathode. The water was from the tap and where I live is very hard. I was using about 20V between the two electrodes. As I applied the voltage,...
5
votes
1answer
2k views

Butler-Volmer equation with concentration dependence?

For a simple elementary reaction on electrode \begin{equation} O+e^-\rightleftharpoons R \end{equation} We can derive the Butler-Volmer equation. But it seems that the formula found on John Newman's ...
5
votes
1answer
89 views

Is the subtrahend in the Nernst equation related to ohmic drop?

Let us consider the Nernst equation $$E= E^\circ -\frac{2.303RT}{nF} \log Q$$ which once at $\pu{298.15 K}$, is the equivalent of $$E= E^\circ - \frac{0.059}{n} \log Q .$$ Does the part of the ...
5
votes
1answer
663 views

How can Nernst equation apply in this redox reaction?

$$\ce{CuSO4 + Zn -> ZnSO4 + Cu}$$ What is the cell potential of the voltaic cell with copper and zinc electrodes if the system is at 50 degrees and the solutions are both at 1 mol? How can it ...
5
votes
2answers
853 views

How much electricity could be generated by a person's stomach acid?

Motorola has a device that is powered by stomach acid. Given that a battery consumes the electrolyte as it generates a charge, how much power could be generated using a device such as this? Let's ...
5
votes
1answer
157 views

Measuring distance in a conductive liquid

What is needed to measure distance between two electrodes imersed in seawater ? I have tried measuring the voltage across the path (a suposed resistance) with a constant current source (about 10uA) ...