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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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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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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283 views

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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116 views

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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115 views

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 help me on this ...
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2k 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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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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Hydrogen peroxide and glycerol combination

Is the mixing of store-grade hydrogen peroxide 3% and glycerol in the ratio of 1:2 (V/V) at room temperature affecting the decomposition rate of hydrogen peroxide?
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Will (3R,4S,5R)-1,3,4,5,6-pentahydroxyhexan-2-one tautomerise in nitric acid?

The following question was sent to me .The question is " Which of the following is A ?" The given answer was a,b,c Background If both ends of an aldose chain are oxidized to carboxylic ...
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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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147 views

Which functional group gets reduced first?

The following is a reduction reaction. In the reduction of 2 to 3, keto group undergoes reduction by nucleophillic addition. Ester could undergo nucleophillic acyl substitution to give an aldo group, ...
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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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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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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 voltmeter ...
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1answer
738 views

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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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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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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148 views

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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Two cells are connected in series. If x g of silver are deposited in cell 1, what volume of oxygen is given off in cell 2? [closed]

I got the answer correct but I'm pretty sure my methodology was wrong. How would you solve such a question?
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568 views

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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212 views

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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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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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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183 views

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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1answer
281 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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The equivalent weight of HNO3 in the following reaction [closed]

The equivalent weight of HNO3 in the following reaction is ‘x’, then the value of x/21 is 3Cu+8HNO3⟶3Cu(NO3)2+2NO+4H2O in this I atempted by using redox formulas but my answer is comming 1 but ...
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888 views

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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524 views

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

There is a list of standard electrode potentials at 298 K from the p. 23 of IB Data Booklet 2016. Which of the following equations (forward/backward reactions), from the two possible ones involving ...
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What defines a discharged battery?

In the case of an AA Alkaline battery, what actually happens inside the battery once it is fully discharged? What components of the battery change as we use it?
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Redox Combustion Reactions

Consider a combustion reaction like the complete combustion of ethane. Here is what I have for the complete combustion as well as the oxidation and reduction: $$\ce{\overset{-3}{C}_2\overset{+1}{H}_6 +...
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695 views

Equation for reaction between chlorine fluoride and potassium bromide

The equation given in the answer key was $$\ce{ClF + 2KBr → KCl + KF + Br2}$$ However won't the $\ce{KCl}$ also react with $\ce{ClF}$ to form $\ce{KF}$ and $\ce{Cl2}$, resulting in the net reaction ...
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What is the flow of electrons, cations, and anions in a voltaic cell (please see image attached)?

This is an IB question. The mark scheme says that the correct answer is A and only A. But I believe B is also correct. The following is my thought process. Since A is more reactive, it undergoes ...
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113 views

What do electrons usually do when lead acid battery is idle?

Lead acid batteries operation are governed by Redox reactions for charging and discharging. But, what do electrons usually do when lead acid battery is idle? And why? Assumptions: Say more ...
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Reduction Potentials [closed]

Standard electrode potential values can be used to judge the reducing ability of a metal. When I was introduced to this topic a simple picture was painted: you put a metal into a solution of its ions. ...
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187 views

Confusion on electrode potentials

Standard electrode potential values can be used to judge the reducing ability of a metal. When I was introduced to this topic a simple picture was painted: you put a metal into a solution of its ions. ...
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1answer
57 views

Determining the half-reaction equations for extraordinary redox reaction? [closed]

I have the following question stated in the science teacher exam: Write the half-reaction equations for the following reaction by using oxidation numbers: $$\ce{Na2SO3 + Na2CrO4 -> ...
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1answer
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The role of temperature in Nernst equation

When measuring a non-standard voltaic cell’s electrode potential, regardless the standard conditions, as long as the concentration of product and reactant the same, a non-standard cell’s potential ...
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1answer
56 views

Understanding the setup of a chemistry lab about redox

In chemistry lab we were looking at oxidation and reduction reactions. To determine the relative activity of several metals we observed reactions between the metals and aqueous solutions of dissolved ...
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575 views

Will hydrogen chloride dissolved in ethanol react with magnesium?

Magnesium will react with aqueous HCl to form magnesium chloride and hydrogen gas. Simple. But I've just read in my textbook that HCl in a solution of ethanol no reaction will take place. There is no ...
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The effect of a voltmeter on the electron flow of a voltaic cell

Due to a voltmeter’s strong resistance nature, how could electrons flow from anode to cathod? It is more reasonable to assume that a voltmeter would stop the redox reaction because the electrons could ...
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Where does Free Energy go in a Redox Reaction?

This doubt came to my mind while answering the following question: Why does a voltaic cell not operate unless the two separate compartments are connected by an external circuit? The answer seems ...
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No sign flipping while figuring out the emf of voltaic cell?

I learnt that for a voltaic cell, the value for the $E_\text{cell}^\circ$ when the reaction is spontaneous is given by $$E_\text{cell}^\circ = E_\text{cathode}^\circ - E_\text{anode}^\circ, \label{...
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Why does increasing the concentration of oxidizing agent decrease the E° in a galvanic cell?

In a galvanic cell, when we add ions of the oxidation agent (in this example, Zn2+) to the anode solution, it decreases the cell potential. However, if the Zn2+ ions aren't involved in the redox ...
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772 views

Formamide and Hoffmann Bromamide Reaction

I encountered a problem to identify the compound which does not give Hoffmann bromamide degradation reaction. One of the options was formamide, and it was given as the answer. Why can't formamide ...
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1answer
2k views

Potassium Manganate and Acidified Potassium Dichromate colour changes [closed]

I would be obliged if somebody could explain the colour changes for the reduction of potassium manganate and acidified potassium dichromate. I understand that for potassium manganate, it is being ...
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1k views

Why is fluorine a oxidising agent? [closed]

An oxidizing agent pulls the electron cloud of the substance being oxidized towards itself, for example: $$\ce{F2 + 2 X- -> 2F- + X2}\qquad (\ce{X} = \ce{Cl}, \ce{Br}, \ce{I})$$ We also know that ...
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Kinetic model of proton reduction

One of my colleagues is working on a homogeneous catalyst ($\ce{X}$) for proton reduction. The simplified proposed mechanism for it is the following. $$\ce{X + 2 e^- ->[$k_1$] X^{2-}} \tag{1}$$ ...
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Instead of using an Ag/AgCl electrode, can I simply use another beaker and connect it to my solution via a salt bridge? [closed]

I'm trying to perform a potentiometric titration as part of my high school laboratory work, by reducing iron(III) to iron(II), and measuring the voltage change as I add cobalt(II) (to reduce it). The ...
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145 views

How much of Ag has formed on the Cu tile?

$\pu{9.547 g}$ $\ce{Cu}$ tile is added to an $\ce{AgNO3}$ solution. After some time, $\ce{Cu}$ was taken out of the solution, washed, dried and weighed. The mass appeared to be $\pu{9.983 g}$. How ...
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1answer
64 views

Why this redox equation occurs on basic medium?

I have the following redox equation that I need to balance: $$\ce{MnO4-(aq) + SO3^2-(aq) → MnO2(s) + SO4^2-(aq)}$$ The problem says that it happens on basic medium, but I don't see the $\ce{OH-}$ ...

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