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Questions tagged [redox]

Redox is the portmanteau of reduction and oxidation. This tag should be used in questions where both the reduction and the oxidation process are under focus. This tag is not limited to inorganic chemistry. If the question is specifically about either reduction or oxidation (not both) of an organic compound, use [organic-reduction] or [organic-oxidation] instead.

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Burning magnesium ribbon

I know that this might sound wrong but, in the reaction $$\ce{2 Mg(s) + O2(g) → 2 MgO(s) + energy}$$ isn't oxygen supposed to be oxidised as it has excess electrons $(\ce{O^2-})$ and can donate a ...
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Equivalent weight in case of disproportionation reaction

We all know that $\text{Equivalent weight} = \frac{\text{Molecular weight}}{\text{n-factor}}$ However consider a reaction like: $\ce{Br2 + OH- -> Br- + BrO3- + H2O}$ where oxidation numbers of $\...
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Reaction between copper and silver(I) nitrate in aqueous medium

What is the reaction between $\ce{Cu}$ and $\ce{AgNO3}$ taking place in aqueous medium? The answer given was: "Only" oxidation of $\ce{Cu}.$ My concern is: how is only oxidation of $\ce{Cu}$ ...
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Redox problem involving Na2S and HSO4- [on hold]

I'm trying to complete a question on an assignment that says Show all steps in determining the number of electrons an atom of sulfur loses when it changes from sodium sulfide to hydrogen sulfate ...
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2answers
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Can lead(II) oxidize tin metal in aqueous solution?

According to my textbook, element $\ce{X}$ can oxidize element $\ce{Y}$ if $\ce{X}$ was lower in the activity series. Lead is lower than Tin in the activity series table in the textbook, but the ...
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2answers
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Is this balanced redox equation correct? [closed]

I'm trying to balance an equation using oxidation numbers $\ce{MnO4^- + H+ + Cl- -> Mn^2+ + Cl2 + H2O}$ my suggestion: $\ce{MnO4- + 8H+ + 5Cl- → Mn^2+ + 2.5Cl2 + 4H2O}$ the 2.5 $\ce{Cl2}$ is ...
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242 views

Reason of dissociation of water molecule in electrolysis

$\ce{H2O}$ molecule is dissociated into $\ce{OH-}$ and $\ce{H+}$ ions on reduction at the cathode in electrolysis. But what happens at the atomic level to $\ce{H2O}$ that proton and hydroxide ions get ...
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How do metals split the oxygen double bond during corrosion?

For a metal like $\ce{Mg}$ to corrode into $\ce{MgO}$, the double bond in $\ce{O2}$ must break. Since the dissociation energy of $\ce{O2}$ is 500 kJ/mol, using estimates from the Boltzmann ...
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1answer
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Why does hydrogen burn spontaneously in fuel cell at room temperature?

It's well known that if you mix $\ce{H2}$ and $\ce{O2}$ in ambient conditions, the $\ce{H2}$ will be stable indefinitely, and will only react with $\ce{O2}$ to form water when ignited by a flame. The ...
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1answer
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Redox titration or iron(II)

The concentration of $\ce{Fe^2+(aq)}$ can be determined by a redox titration using A. $\ce{KBr}$ B. $\ce{SnCl2}$ C. $\ce{KMnO4}$ (basic) D. $\ce{KBrO3}$ (acidic) Can anyone please ...
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83 views

Reaction of potassium with water

In general, when we put potassium into water, it will produce potassium hydroxide and hydrogen: $\ce{2K + 2H2O ⟶2KOH + H2}$ However isn't the following reaction also possible? $\ce{2K + H2O ⟶K2O + ...
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Products of Redox Equations [duplicate]

I was just wondering how would you know the products of a redox equation, or if that could even be derived from just knowing the reactants. For example when Potassium permanganate reacts with a ...
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How to write equations for a reaction of metals with water

Please write two equations for reacting lithium with water and barium with water. Make sure to add the states of matter after each compound. Currently, for lithium I have the equation $$\ce{2Li(s) +...
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3answers
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Can Iron(III) oxide oxidize elemental iron in a nitrogen environment under room temperature without any catalysis? [closed]

Will there be electron transfer to allow this process to happen: $\ce{2 Fe(III) + Fe(0) -> 3 Fe(II)}$
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Reaction mechanism of combustion of hydrogen

After a discussion about the usefulness of hydrogen fuel for cars with a friend of mine, I wondered what the reaction mechanism for combustion of $\ce{H2}$ was. I only study (well almost) organic ...
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Sulphuric acid in as oxidant [duplicate]

I find difficult to understand how do I get to the products of the following reaction: $$\ce{2NaBr(s) + 2H2SO4(aq) -> Br2(l) + SO2(g) + Na2SO4(aq) + 2H2O(l)}$$ after checking the oxidation ...
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Reaction of DIBALH with alkyl cyanides

I was recently studying reactions involving DIBALH (diisobutyl aluminium hydride) and saw that it's reaction with alkyl cyanide yielded R-CH2NHOH according to Jerry March whereas in Solomons the ...
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1answer
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What are the half reactions for the redox reaction between SO2 and iodine?

What are the half reactions for the redox reaction between $\ce{SO2}$ and iodine? The relevant chemical equation: $$\ce{ SO2 + H2O + I2 -> H2SO4 + 2HI}$$ This is what I think it is, not sure if ...
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1answer
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Reaction between copper(II) iodate and iodide

I was attempting the following question from IChO 1989, which involved balancing of redox equations. One may just expect this to be a typical iodate-iodide redox reaction, usually employed in ...
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2answers
240 views

Leaching of copper using zinc

Why can we not use zinc for extracting copper from a solution containing $\ce{Cu^2+}$ ions even though it is a better reducing agent than $\ce{Fe}$? I am studying metallurgy and I cannot understand ...
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Electric potential of a redox reaction (without solids)

I need someone to help me with a problem: We have a solution which is $\pu{0.1 M}$ of $\ce{KMnO4}$ and $\pu{0.1 M}$ $\ce{Fe^2+}$ and has $\mathrm{pH}=0$. Given the electrical reduction potential of ...
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Determine the oxidation number of sulfur in SF6

I've just started learning about redox chemistry and oxidation numbers. I can work out most of the oxidation number questions, but I don't know how to determine the oxidation number of sulfur in $\ce{...
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Can a cation form a bond with only the oxygen in hydroxide ion?

$$\ce{Al2O3 + 2 NaOH → 2 NaAlO2 + H2O}$$ In this reaction between an amphoteric oxide and a base, I do not understand how $\ce{Al}$ makes a bond with oxygen atoms since the water is found in the ...
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Does reduction/ oxidation take place separately at a half cell electrode?

In the redox reaction chapter, we learn that oxidation and reduction go hand in hand. The oxidising agent oxidises by accepting the electron released by the reducing agent and gets reduced in the ...
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1answer
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Why do Cu⁺ ions spontaneously form copper metal and Cu²⁺ ions in solution?

The standard electrode potentials for three reactions involving copper and copper ions are: $$ \begin{align} \ce{Cu^2+(aq) + e- &-> Cu+(aq)} &\quad E &= \pu{+0.15 V} \\ \ce{Cu^2+(...
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3answers
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What is the strongest oxidising agent?

I searched for the strongest oxidising agent and I found different results: $\ce{ClF3}$, $\ce{HArF}$, $\ce{F2}$ were among them. Many said $\ce{ClF3}$ is the most powerful as it oxidises everything, ...
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Why does the following “Battery” experiment work?

I did the following experiment: Experimental setup: Two electrodes (one made out of Iron,the other made out of Copper) are put into a (bluish) Copper(ii) sulfate lotion. Then, one connect a ...
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1answer
374 views

What do the half-reactions need to be for balancing a redox reaction in an acidic medium?

Balance the following reaction: $$\ce{CuS + SO4^{2-} -> CuO + SO2}$$ Below, the number mentioned in the parenthesis is the oxidation number of sulfur. I have found out that the oxidation half-...
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1answer
42 views

Disproportionation of 2 KO₂ + 2 H₂O → 2 KOH + H₂O₂ + O₂

How is the following reaction a disproportionation reaction? $$\ce{2 K\overset{-1/2}{O}_2 + 2 H2\overset{-2}{O} ->2 KOH + H2\overset{-1}{O}_2 + \overset{0}{O}_2}$$ In this, the OS are $-1/2$, $-2$...
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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 ...
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Nitrate reaction with iron minerals

I am trying to find literature or an answer to what happens to nitrate as it comes in contact with iron oxides. Does the nitrate get reduced to ammonium in all cases of iron(II/III) oxides? What is ...
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Can carbon dioxide be used as oxidant for iron?

Determine whether it is possible for $\ce{CO2}$ to be an oxidant for $\ce{Fe}$. Justify your choice by comparing the corresponding half reactions. I found the following half-reactions, both on ...
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1answer
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How can I find the emf of a cell given the individual reduction and oxidation reactions and their respective potentials? [duplicate]

If I am given the individual oxidation and reduction half-equations, how can I find the emf of the combination? For example: $$ \begin{align} E^\circ(\ce{Fe^3+}/\ce{Fe^2+}) &= \pu{0.77 V}\\ E^\...
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What is the mechanism of the Clemmensen reduction?

I have learned that we can reduce a ketone to an alkane using the Clemmensen reduction, where we treat the ketone with amalgamated zinc in the presence of $\ce{HCl}$. My book didn't mention the ...
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1answer
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In a galvanic cell, why do electrons move through the wire from zinc to copper?

I understand that there is aqueous $\ce{Cu^2+}$ in this scenario which pulls on the electrons from the zinc causing the electrons to move through the wire, but how does the electronegativity of $\ce{...
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1answer
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Reverse Cannizzaro reaction to make aldehydes?

Is it possible (and practicable) to reverse Cannizzaro reaction (disproportionation of aldehydes to carboxylic acids and alcohols) to produce aldehydes from carboxylic acid and alcohol without need to ...
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1answer
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Will heating of KClO3 be considered disproportionation?

In all examples of disproportionation I have seen, there is one particular atom whose oxidation state is both increasing and decreasing to give rise to different products For example, on heating ...
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1answer
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Why do alpha-hydroxy ketones respond positively to Tollens', Fehling's, Benedict's, Schiff's and HgCl2 tests?

I learnt from a certain textbook that aldehydes and formic acid respond positively to Tollens', Fehling's, Benedict's, Schiff's and HgCl2 tests. However, in another textbook I read that even alpha-...
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Why does temperature affect cell potential?

The Nernst equation describes the relationship between cell potential and temperature. But why does temperature affect cell potential? My understanding is that the collision model of kinetics is not ...
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1answer
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Corrosion of iron: no electron pushing mechanism?

Why does the oxidation-reduction reaction between iron, water, and $\ce{O2}$ gas to form rusts lack an electron pushing mechanism and a specific sequence of steps? $$\ce{4Fe^0(s) + 3 O2(g) + 2n H2O(l)...
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1answer
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Experimental measurment of thiosulphuric acid decomposition kinetics

Problem I am trying to do a kinetics analysis on the following reaction: $$\ce{Na2S2O3 {(aq)} + 2 HCl {(aq)} -> S {(s)} + 2 NaCl {(aq)} + SO2 {(g)} + H2O {(l)}}$$ Suggested Method However, most ...
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1answer
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What is the balanced chemical equation for a redox reaction between a lithium-cobalt battery and a graphite electrode?

I'm doing a project for my last year of secondary school on lithium cobalt batteries and got confused about the equation. This is the only equation I can find (source: www.science.org.au): \begin{...
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Negative Voltage for Full Redox Reaction?

I have a question about voltages including redox reactions. I know that half equations may have negative voltages when choosing what is undergoing reduction, and what is undergoing oxidation in a ...
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1answer
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How does calcium chloride act as a sequestrant (food science)?

This Wikipedia page lists common sequestrants (with respect to food science). As stated on the page: A sequestrant forms chelate complexes with polyvalent metal ions, especially copper, iron and ...
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Half equations for H2O2 for its reducing and oxidising nature in acidic and alkaline medium

Is there a complete list of all the half equations for $\ce{H2O2}$ - both oxidation and reduction, in acidic and alkaline conditions? I've looked on the internet but can't seem to find a list with all ...
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1answer
2k views

Why does NaCl act as a catalyst for the reaction of CuSO4 + H2O + Al?

I am analyzing a reaction between water sulfate copper and aluminum. A chunk of $\ce{Al}$, e.g., aluminum foil. I realize that a layer of $\ce{Al2O3}$ forms on the surface of the $\ce{Al}$, ...
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1answer
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Does cathodic protection work for air oxidation?

I'm not expert in cathodic protection, but does it work with metals under air oxidation? Is it possible to protect a metal from air oxidation by applying an electrode to it? Or it has to be inside an ...
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1answer
52 views

Oxidation of Sodium Hydroxide in Ethanol?

So I read recently that: Alcoholic solutions of sodium hydroxide will oxidize in air, turning brown. First is this true? And if so what is oxidizing? I can't think of what sodium hydroxide ...
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Reduction of oximes with lithium aluminium hydride

I know that $\ce{LiAlH4}$ is good a reducing agent and it donates hydride ions but then I am not able to understand the mechanism of this reaction. I attempted this way I am not understanding what ...