22 votes
Accepted

Why does the Co³⁺/Co²⁺ couple have such a high reduction potential?

The electronic configuration has nothing to do with it. The reduction potentials of $\ce{Ni^3+}/\ce{Ni^2+}$, $\ce{Cu^3+}/\ce{Cu^2+}$ and $\ce{Zn^3+}/\ce{Zn^2+}$, if they have been/could be measured, ...
orthocresol's user avatar
22 votes
Accepted

Can carbon dioxide be reduced to carbon monoxide and oxygen to produce energy?

Unfortunately, the question as stated is thermodynamically impossible. Let's look at the proposed reaction: $$\ce{CO2(g) -> CO(g) + O(g)}$$ This reaction is simply a bond dissociation (specifically,...
Nicolau Saker Neto's user avatar
12 votes

Why exactly are standard potentials additive?

Following on Derek's great answer, it is very important to remind that the conventional way we use to add half-cell potentials is a consequence of the conservation of energy. Therefore, we should look ...
truffaut's user avatar
  • 311
12 votes
Accepted

Cyclic Voltammetry - HOMO and LUMO levels

Yes, you can "convert" this way, but you're correct to be skeptical. Let's start with interpreting the cyclic voltammetry curves themselves. (figure from Wikipedia) Note that the "peak" actually ...
Geoff Hutchison's user avatar
10 votes

Can carbon dioxide be reduced to carbon monoxide and oxygen to produce energy?

You’re looking at bond dissociation energies. They, however, do not give a good picture. A better place to start looking is the standard enthalpy of formation. The linked Wikipedia article provides an ...
Jan's user avatar
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9 votes
Accepted

What exactly is formed when K2Cr2O7 is reduced?

The dichromate ($\ce{Cr2O7^2-}$) ions are strong oxidizing agents at low pH. During the redox process, each chromium atom in the dichromate ions (oxidation state = +6) gains three electrons and get ...
Mathew Mahindaratne's user avatar
9 votes

Why is hypochlorite a stronger oxidizing agent than other oxychlorides?

First, hypochlorite ($\ce{ClO−}$) is not a strong oxidizing agent compared to other chloride oxyanions, at least in acidic medium. Under standard conditions in acidic medium, chlorous acid ($\ce{HClO2}...
Mathew Mahindaratne's user avatar
8 votes
Accepted

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

The half-potential you've given for strontium is only for the first ionisation. The half-potential you'd actually get is $\pu{-2.899 V}$ for the stable dication to give a cell potential of $\pu{5.769 ...
gsurfer04's user avatar
  • 1,286
8 votes
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Will nitrate be able to oxidise mercury?

It would really help if you copied the entire half cell reaction. The atoms must balance in a valid half cell reaction! So there are: \begin{align} \ce{NO3− (aq) + 2 H+ + e− &<=> NO2 (g) + ...
MaxW's user avatar
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8 votes
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Why chlorate(V) is one of the primary products of disproportionation reaction between chlorine gas and hot concentrated NaOH?

The explanation you have gathered is not correct. $\ce{NaOH}$ is not an oxidizing agent. The conversion of hypochlorite to chlorate is a very complicated reaction so there is no direct formation of ...
AChem's user avatar
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7 votes
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Why is hypochlorite a stronger oxidizing agent than other oxychlorides?

Besides the the thermodynamic aspects discussed by Matthew, consider the kinetic aspects. Oxidation by a chlorine oxyanion involves displacement of oxygen from its bond with the chlorine. Such a ...
Oscar Lanzi's user avatar
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7 votes
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What does the salt actually do during electrolysis?

A salt like $\ce{Na2SO4}$ is essential in electrolysis. It provides ions $\ce{Na+}$ and $\ce{SO4^{2-}}$ which are attracted by the electrodes in the solution and migrate to them. When they arrive near ...
Maurice's user avatar
  • 28.3k
7 votes

Why is my battery of galvanic cells not enough to power a lamp rated for a lower voltage than the battery provides?

It is not a problem of voltage. It is a problem of current and power. Whatever its nominal voltage, your bulb has a power to be known in watts. If your $\ce{Zn/Cu}$ cells are not able to produce the ...
Maurice's user avatar
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6 votes
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Stronger reducing agent

According to this Wikipedia entry: "[electronegativity] is a chemical property that describes the tendency of an atom to attract electrons (or electron density) towards itself. then according ...
airhuff's user avatar
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6 votes

How to refine manganese metal from manganese(IV) oxide found in batteries?

You may heat mixture of $\ce{MnO2}$ with charcoal to higher than $\pu{850 °C},$ in the absence of air. Manganese will be produced in the solid state by reduction of the oxide. But it is sensitive to ...
Maurice's user avatar
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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{+...
orthocresol's user avatar
5 votes
Accepted

Calculating Ratio of Stability Constants

You used all the information from the question except the line that would have helped you solve it The concentrations of iron-containing species satisfy the relations $[\ce{Fe^2+}] = [\ce{Fe(CN)_6^...
orthocresol's user avatar
5 votes

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

gsurfer04 is right that it wouldn't be strontium. If you're going really outlandish and willing to use explosive compounds, then the highest possible cell voltage would be obtained with the following ...
Jacob Johnston's user avatar
5 votes
Accepted

Can molten aluminium be used to reduce iron oxide (rust) into iron?

Short answer: Yes. Take a look at the Ellingham Diagram. The line for aluminium oxide is lower than the line for the all the iron oxides. This indicates greater stability of aluminium oxide, or in ...
getafix's user avatar
  • 8,475
5 votes
Accepted

Electrolysis of water: Which equations to use? (IB Chem)

For the acidic electrolysis, use the reactions where $\ce{H+}$ occurs. As $\ce{OH-}$ is not available in considerable amount there as a reagent, neither it is created as a product. Generally,...
Poutnik's user avatar
  • 41.3k
5 votes

Disproportionation of silver(I) in aqueous solution

It is convenient to solve problems like that with a Latimer diagram, which is a great tool for predicting conditions for the reactions of disproportionation and synproportionation. A generic Latimer ...
andselisk's user avatar
  • 37.6k
5 votes

Why can't iodide be oxidised to iodate in acidic medium?

Permanganate oxidizes iodide to iodine $\ce{I2}$ at all pH values. In acidic conditions, the reaction is finished here. But in basic solution, the iodine $\ce{I2}$ is transformed into iodide and ...
Maurice's user avatar
  • 28.3k
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 $...
Poutnik's user avatar
  • 41.3k
4 votes
Accepted

Will magnesium undergo a redox reaction with zinc(II) or copper(II)?

Let’s assume for a second that magnesium reacts only with the zinc. The reaction would occur according the following equation: $$\ce{Mg + Zn^2+ -> Mg^2+ + Zn}$$ You have already identified, if I ...
Jan's user avatar
  • 68k
4 votes

Can molten aluminium be used to reduce iron oxide (rust) into iron?

Aluminum can indeed reduce iron oxide, but you may not get iron metal. Aluminum and iron constitute one of many pairs of metals that form intermetallic compounds. Reference [1](https://doi.org/10.1007/...
Oscar Lanzi's user avatar
  • 56.9k
4 votes

Prevention of rusting

Galvanizing isn't just a protective coating in the sense that it avoids contact between the iron and the oxidant. Zinc oxidizes more easily than iron, and since both conduct electricity, you can have ...
SendersReagent's user avatar
4 votes

How to calculate the pH of a redox reaction between nickel(IV) oxide and silver?

For the following reaction: \begin{gather} \ce{NiO2(s) + 4 H+(aq) + 2 Ag(s) -> Ni^2+(aq) + 2 H2O(l) + 2 Ag^+(aq)}\\ E^\circ = \pu{2.48 V} \end{gather} Calculate the $\mathrm{pH}$ of the solution if ...
mematusz's user avatar
  • 131
4 votes

Decreasing magnitude of peaks in cyclic voltammogram?

Perhaps your observation is an indication of irreversible reaction conditions. More specifically, a tight deposit on the electrodes hampering the advancement of the electrochemical reactions. This ...
Buttonwood's user avatar
  • 29.7k
4 votes

Single electrode potential measurement

Electrodes transport electrons produced from one half-cell to another, thus producing an electric charge. You need to have a reference value to compare it to in order to obtain the relative potential. ...
Melanie Shebel's user avatar

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