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).

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22 views

Why does the application of external mechanical pressure increase the performance of lithium-ion batteries?

Many electric vehicle batteries - specifically lithium-ion ones considered for this query - can be subjected to external mechanical pressure because it increases battery performance. What components ...
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Orientation of external cell when voltage is supplied by it to voltaic cell so as to oppose its cell potential

Given below is a page from our Chemistry Textbook: As it can be seen, the direction of $E_{ext}$ in figure $3.2(c)$ is opposite to the direction in figures $3.2(a)$ and $3.2(b)$. I understand that $...
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Which is more efficient way to generate energy using hydrogen: direct hydrogen combustion or through fuel cell? [closed]

Which is more efficient way to generate energy using hydrogen: direct hydrogen combustion or through fuel cell? Please explain so that even a primary school student can understand.
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[Co(H2O)6]3+ vs [Co(NH3)6]3+ oxidising water

Cobalt(III) complexes cannot be prepared by addition of the ligand to a solution of the metal cation because the aqua cation $\ce{[Co(H2O)6]^3+}$ has no stable existence in solution. It is strongly ...
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What is 'absorbance power' in electrochemistry?

I have been asked $\ce{250 mL}$ solution of unknown molarity of $\ce{CuSO4}$ in water was electrolysed using platinum electrodes. After the passage of a current $2 \times 10^{-3}$ ampere for $19.3$ ...
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Why do we need salt bridge in a cell during potentiometric measurement as there is no or minimum redox activity at electrodes?

In electrochemical cell, we need salt bridge to maintain electrical neutrility in both halves cells during redox reaction?. But in during potentiometric measurement, no or minimum current is drawn and ...
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what does Area(A) in Randles-sevcik equation refer to? geometrical area of electrode or electrochemical active surface area/

In the Randles-Sevcik equation, $$i_p = 0.4463 \ nFAC \left(\frac{nFvD}{RT}\right)^{\frac{1}{2}}$$ we have an area $A$ in the formula. is this the electrochemically active area or geometrical area? ...
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Van Der Waals Interactions [closed]

The radius of one sphere is 5 nm, and another sphere is 10 nm. Determine the van der Waals interaction for the following conditions: a) Distance between the spheres is 20 nm and the hamaker constant ...
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Water electrolysis [closed]

What happens when the power source is cut off from the electrodes? Do the electrons that travelled from the anode to cathode return back to the anode? Are the electrodes re-usable?
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Reduction Potential of Fe[(C2O4)3]3- /Fe2+

I need the standard reduction potential of the couple $\ce{[Fe(C2O4)3]^3-}$ / $\ce{Fe^2+}$ . I searched for it in many reduction potential tables on the web in vain. If someone can tell me where to ...
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How can the difference between surface energy and electrostatic repulsion be calculated in electroplating?

When metals are electroplated unto surfaces, there are a myriad of forces at play. To set a clear example, if one were to electroplate a magnet with a diamagnetic metal such as bismuth, there will be ...
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Electrodes selection in electrolytic cell [closed]

In electroplating, why is metal to be electroplated connected to positive terminal of the battery only????
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What is exactly molar conductivity? [closed]

I know molar conductivity is conductivity of solutions by molarity, but then I see on next page of my book it defines molar conductivity $\Lambda$ as follows: $$\Lambda = \frac{\kappa a}{l},$$ where $...
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Why is HNO3 a stronger oxidising agent than H3PO4?

Why is $\ce{HNO3}$ a stronger oxidising agent than $\ce{H3PO4}$? $\ce{N}$ and $\ce{P}$ have the same oxidation number. Is it the electronegativity difference between $\ce{N}$ and $\ce{P}$?
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Entropy change during electrolysis of water

Consider the electrolysis of water reaction: $$\ce{H_2O -> H_2 + 1/2O_2}$$ At room temperature and atmospheric pressure, the change in enthalpy of this reaction is $\Delta H = \pu{+286 kJ mol-1}$. ...
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1answer
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Considering Gibbs energy or electrode potential to find disproportionation tendency

The following data was given (without the asterisks and footnote) asking us to find the oxidation states that would have a tendency to disproportionate - By tendency to disproportionate, I understood ...
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Thickness of proton exchange membrane (Nafion)?

I am looking into using a proton exchange membrane for a bio-energy cell experiment. Previous scholars have been using Nafion as a PEM to place between the anode and cathode (air-cathode). the ...
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What is the reason for decomposition of layered cathode materials?

Articles like this claim oxygen can evolve from layered metal oxide cathode materials when charging the Li-ion battery. Is it the high positive potential given to the cathode while charging pulling ...
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Why can we disregard stoichiometric coefficients when computing reduction potentials?

A $\ce{Cr(s) | Cr^3+ || Cd^2+ | Cd(s)}$ galvanic cell has redox half reactions: $$ \begin{align} \ce{Cd^2+ + 2e- &-> Cd(s)} &\quad E^\circ &= \pu{-0.4 V}\tag{R1}\\ \ce{Cr^3+ + 3e- &-...
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1answer
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Conductance and concentration of a strong electrolyte

I learnt that with the increase of concentration, conductance of tr electrolyte decreases. While looking for the reason I found in my textbook that if concentration increase, amount of ions increases ...
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Electrochemical etching of silicon

I am doing some research on porous silicon in electrochemical biosensors. I have come across the electrochemical etching method to produce porous silicon for the biosensors. I have also come across ...
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faraday laws of electrolysis

I came across this question: A quantity of electrical charge that brings about the deposition of 4.5 g $\ce{Al}$ from $\ce{Al^{+3}}$ at cathode will also produce the following volume (STP) of $\ce{H2}...
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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 ...
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Cathodic protection

My doubt is regarding cathodic protection. I have understood protection of metal by using sacrificial anodes as its a clear example of an electrochemical cell. However, in ICCP we make a less reactive ...
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What an electrolyte “really” does in electrolysis?

I am reading about electrolysis and I have trouble to understand why an electrolyte must be added in order for electrolysis to occur. I have read this question but still can't get it. The definition ...
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In a perfect electrolytic cell, would the anode and cathode change by the same amount

If I had a theoretically perfect electrolytic cell, such as one with Copper anodes and cathodes, and a copper nitrate solution, over a given time period with a voltage applied, would the change in ...
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Potential difference between metallic electrodes in water

If I dip two pieces of metal in tap water I measure a potential difference between the two electrodes with a common digital voltmeter. For example, for Cu and Al I measured 0.55 V and for Cu and Fe I ...
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1answer
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Why Does Electrical Work Cause Changes in Internal Energy of the System? [closed]

If we look at system at constant temperature and volume which is galvanic cell, first law of thermodynamics states: $$ dU = dQ + dW'$$ Where W' is electrical work exchanged with surroundings and Q is ...
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What are the half-cell redox reactions of water in different pH solutions?

While reading about the electrolysis of aqueous sodium chloride solution, I realized that the half-cell reactions depend on the pH of the solution. According to my understanding, the following ...
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Why are conductance and conductivity additive in nature? [closed]

In my book, it is written that: $κ_{electrolytic solution} = κ_{electrolyte} + κ_{solvent}$ $G_{electrolytic solution} = G_{electrolyte} + G_{solvent}$ Where $κ$ and $ G$ are conductivity and ...
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What are the similarities / differences between the terms anode / cathode and oxidizing agent / reducing agent? [closed]

I'm kind of confused on how to distinguish the terms anode and cathode from oxidizer and reducer or oxidizing agent and reducing agent. Some references prefer to use one over the other in discussions ...
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What if kinetic energy of ejected electron = 0

When hf ≥ work function, Then the electron still comes out. So, if I say kinetic energy of ejected electron = 0, it should still come out. Right ? Then, how does the electron even move out or gets ...
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Calculating time needed to coat an object using the process of electrolysis

Suppose we have an object with a surface area of $S=\pu{1.5 dm2}$, and we need to coat it with hard chrome. The thickness of the coat should be $d=\pu{80 \mu m}$. The mixture used for coating is of ...
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What does the horizontal axis on cyclic voltammograms mean?

In cyclic voltammograms (like the one in the attached image) what exactly is the horizontal axis' voltage refering to? Is it the measured voltage between the reference electrode and working electrode? ...
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What Does Electrical Work Represent in Context of Electrochemical Cells?

If cell operates reversibly than change in Gibbs energy of system equals electrical work of the cell. As far as I know electrical work is work done by electric field when charge moves between certain ...
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How to measure chlorine content using ORP sensor?

In my project I need to measure pH, turbidity, and chlorine level of treated drinking water. I found sensors for measuring pH, turbidity, and also chlorine. The actual problem begins is that the cost ...
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2answers
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Does a zinc metal coating react with coffee in a coffee grinder?

I'm restoring an old coffee grinder and I want to give the grinder mechanism a nice zinc / silver coating. But I read it is not safe for zinc to be in contact with acidic foods. When I look at the ...
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1answer
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Can you create a temporary bond in between an atom and a filter by electrically charging the filter?

I want to be able to turn a filter on and off by electrically charging the filter so that it creates a temporary bond that blocks up the filter then, by discharging the filter, releasing the temporary ...
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Enthalpy of Reaction and Efficiency of Electrochemical Energy Devices

For electrochemical energy devices such as batteries or fuel cells working reversibly, efficiency is defined as: $$ \eta = \frac {\Delta_rG^⦵} {\Delta_rH^⦵} $$ Since cell operates reversibly Gibbs ...
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Calculating the value of equilibrium constant using cell potential differences

Calculate $\Delta G^\circ$ and $K$ at $\pu{25 ^\circ C}$ for the following reactions. (a) \begin{align} \ce{Cu^2+ + 2e- &-> Cu}\quad E^\circ = \pu{0.34 V} \\ \ce{Fe^3+ + e- &-> Fe^2+}\...
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Grotthuss mechanism and diffusion of hydroxyl ions

Does a new water molecule form and result in a new hydroxide being formed?
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How does the membrane potential change so drastically during an action potential?

I understand that the Nernst potentials $$V = \frac{k_\mathrm{B}T}{e} \ln\left(\frac{c_\mathrm{out}}{c_\mathrm{in}}\right)$$ for all ions inside and outside a cell barely change when an action ...
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How does an anode metal come into solution if it cannot react with an electrolyte?

From what I understand, an anode material is chosen so that it does not react with the anode electrolyte solution. I was just wondering, then, that when you have a galvanic cell which has a Mg metal ...
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1answer
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How is it possible to electroplate using an Al3+ solution, when water is a stronger oxidant?

Suppose that I wanted to electroplate Al(s) onto a Cu(s) Cathode, (using an Aluminium Nitrate solution and Al(s) anode). At standard conditions, Al(s) is the strongest reducing agent, which is good. ...
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What is a suitable material for a cathode in electroplating experiment?

I am going to do an electroplating experiment, whereby I will be using a Cu(NO3)2 solution to plate onto a cathode. What is an easily accessible cathode which I can use for this? Would a strip of Ag (...
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Why do galvanic cells need a salt bridge while electrolytic cells don't?

I see the questions of why a galvanic cell needs a salt bridge and why a electrolytic cell doesn't need a salt bridge being answered separately but I still can't grasp why you are not allowed to mix ...
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Will an alloy leaching in an acid act as both anode and cathode?

If an alloy is placed in an acid where selective leaching is occurring, will the alloy act as both anode and cathode? If the alloy does act as both anode and cathode then will the potential difference ...
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1answer
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More ions form pairs when concentration of acid increases, does that decrease the speed of reaction?

Electrical conductivity decreases as an acid becomes more concentrated because more ions form pairs. However, does that affect the speed of reaction of the acid as there is a smaller concentration of ...
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219 views

Electrochemistry - Redox & Electroplating

I've stumbled across an electrochemistry problem that I need help on: $$\ce{Fe~|~Fe^{+2}~||~Cl^{-},Cl2~|~Pt}$$ I understood that iron is at the anode and is being oxidized, however I do not know ...
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1answer
1k views

Variable oxidation state of transition metal ions

Transition metals can form stable ions with different oxidation states. But I am confused why doesn't only the most stable state exist. Let me clarify my question more: $$\ce{Ti^{2+} -> Ti^{3+} + ...

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