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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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Why is sulfuric acid used in the Jones oxidation of alcohols?

When oxidising primary alcohols, $\ce{K2Cr2O7}$ is used because it's a useful & readily available oxidising agent. Why does the sulfuric acid need to be added? Does it have to do with the ...
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1answer
30 views

Potassium Manganate and Acidified Potassium Dichromate colour changes [on hold]

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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How to determine the iron content in spinach from a titration with permanganate solution?

I used titration to find the mass of iron in a $5~\mathrm{g}$ sample of spinach after leaving the spinach to soak in tap water for 5 different amount of times. I added $\ce{H2SO4}$ to the solution and ...
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1answer
175 views

The reaction of iron with sulfur to produce Iron(II) sulfide is inconvenient (for me)

I am taking a lot of iron properties this semester, but I have found some contradicting piece of information about the reaction of iron with nonmetals illustrated with two cases \begin{align}\ce{ **...
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What is the difference between galvanization and sacrificial protection?

If we use zinc in both methods, then the same process occurs: zinc corrodes in preference to iron, and eventually zinc has to be replaced. So what's the difference?
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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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1answer
516 views

Why do disproportionation reactions take place?

I want to know what are the conditions when disproportionation reaction is feasible. Is it just because of stability factors or it has other dimensions to it. As an example: $$\ce{3HNO2 -> HNO3 + ...
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1answer
35 views

Do the salt bridge ions have to match the ions in the half-cells solutions?

Does the salt bridge in a galvanic cell have to have the same ions as the ones in the solutions? E.g. does it need to have nitrate ions if the half-cells contain copper nitrate and zinc nitrate, or ...
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2answers
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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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23 views

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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1answer
33 views

What is the first ionization energy of the hydride ion?

What is the first ionization energy for hydride? Since there are two electrons in the s orbital, I suppose it should be more stable than hydrogen, despite the extra electric charge, so the ionization ...
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Does Br2/H2O oxidize all aldehydes?

In many books, it is mentioned that aldehydes are easily oxidized even by mild oxidizing agents. However, I have never seen bromine water explicitly mentioned. But in the carbohydrates chapter, it is ...
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1answer
123 views

Removing Rust with Coke

I've seen a few videos on cola being used to remove rust, I've tried it myself too so I know that it works. Now the thing that's bothering me is that this apparently contradicts what I've learnt ...
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1answer
43 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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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 ...
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2answers
120 views

Acidic, Basic, and Neutral Medium

So I'm new to this concept and I can't find any proper explanation to this. What does it mean for a reaction to occur in an acidic, basic, or neutral medium?
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1answer
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Why is water instead of hydroxide ions used to balance oxygen atoms in redox half equations?

When balancing half equations of redox reactions, $\ce{H2O}$ is used to balance any oxygen atoms? For example, this half equation $$\ce{NO3- → NH4+}$$ is balanced into: $$\ce{NO3- + 8 e- + 10 H+ → ...
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2answers
807 views

Sodium Polysulfide production from NaOH and Sulfur

Does the sulfur also oxidize the $\ce{OH-}$ radicals after the $\ce{Na2S4}$ chains form? Something like this: $$\ce{9S + 4NaOH -> 2Na2S4 + SO3 + H2O}$$
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1answer
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Is electrolysis of molten silver nitrate possible? [duplicate]

Since the salt is molten, the only ions are $\ce{Ag+}$ and $\ce{NO3-}$, and both of them can only do a reduction reaction. Who goes to the anode? Also, there is no acid in the solution — only the salt ...
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1answer
18 views

Can a half-reaction be oxidation if it has the higher reduction potential?

I am working on a problem that provides these two half-reactions: $$ \begin{align} \ce{Fe^3+ (aq) + e- &-> Fe^2+ (aq)} &\quad E^\circ_\mathrm{red} &= \pu{+0.77 V}\\ \ce{S2O6^2- (aq) + ...
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38 views

Can a part of a compound be a reducing agent?

I have the equation: $$\ce{2 Cu2O + Cu2S -> 6 Cu + SO2}$$ My doubt is that since copper is reduced (it goes from $+1$ to a $0$ O.S.), then which of the two reactants is reduced? Or why would it ...
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Why iron reacts differently with concentrated and dilute sulfuric acid?

When $\ce{H2SO4}$ is dilute, $ \ce{Fe +H2SO4 -> FeSO4 + H2} $ and when $\ce{H2SO4}$ is concentrated, $\ce{3Fe +8H2SO4 -> FeSO4 + Fe2(SO4)3 + 4SO2 +8H2O}$ What made the reaction with ...
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785 views

Does Temperature Affect Rate of Reaction of Electrolytic Cell

I completed an electrolysis experiment. I used copper electrodes and a copper sulphate solution, and my independant variable was the temperature of the electrolyte. I was just wondering if increasing ...
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1answer
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How do we get NaClO3 in the reaction between Cl2 and NaOH?

From problem no. 4080 in a Russian example exam set: $$\ce{6NaOH + 3Cl2 -> NaClO3 + 5NaCl + 3H2O}$$ How do we get that $\ce{NaClO3}$? I can't seem to guess. I found this explanation on YouTube, ...
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Why is salt needed when using vinegar to clean pennies?

Let's say you have a solution that is vinegar and it has salt ($\ce{NaCl}$) dissolved in it. Then you place old dull pennies in it. Then you look at it 5 minutes later and the pennies are clean and ...
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2answers
2k views

Balancing a REDOX reaction using the oxidation number method, in acidic solution

I am trying to balance the REDOX equation shown below, but I got stuck after balancing the major atoms. Where can I go from here? I know I need to balance the H and O atoms, and make sure the charges ...
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2answers
39 views

Is the reaction involving a proton transfer a redox reaction?

$$ \begin{align} \ce{H2S (aq) + NH3 (aq) &→ NH4+ (aq) + HS- (aq)}\tag{1}\\ \ce{Pb(s) + 2 FeCl3 (aq) &→ 2FeCl2 (aq) + PbCl2 (aq)}\tag{2} \end{align} $$ Which of the following statements ...
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2answers
6k views

Redox: Oxidation and Reduction

I don't get the difference between the gain or loss of electrons in a reaction and changes in oxidation state. Based on my notes and some research: Gain or loss of electrons A substance is oxidised ...
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2answers
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Can compounds (or only elements) be referred to as oxidising and reducing agents?

In the reaction $$\ce{3CuO (s) + 2NH3 (aq) <=> N2(g) + 3H2O(l) + 3Cu(s)}$$ the oxidation number of $\ce{Cu}$ goes from $+2$ in the reactant side to $0$ in the products, and so it is reduced. ...
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2answers
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Waste water treatment [closed]

This is a very simple question: Why are oxidized compounds generally thought to be less toxic/polluting than reduced species? This is used in waste water treatment where oxidizing agents (such as ...
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1answer
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Identifying if reaction is reduction or oxidation. Is there an error in this question?

I am looking at this reaction: I am trying to determine if it is reduction or oxidation. In the initial molecule I calculate the overall oxidation numbers as: ...
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3answers
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Please explain why dioxygen difluoride is so dangerous

I just read this article that mentioned that dioxygen difluoride is very dangerous. The terms it uses are "awful", "violently hideous" and "deeply alarming". But I couldn't get a handle on exactly ...
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0answers
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OF2 vs O2F2 oxidising strength

My teacher said that OF2 is the third most powerful oxidising agent after F2 and atomic O, but I think O2F2 should be even more oxidising, since it less stable than OF2. I just read on quora that O2F2 ...
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2answers
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What gas are the bubbles that evolve in the redox reaction of copper(II) chloride and aluminum?

When aluminum (foil) is placed in an aqueous solution of copper(II) chloride, the aluminum atoms lose electrons to the copper(II) ions and replace them to form aluminum chloride, and to free up ...
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1answer
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Does iron(III) sulfate react with copper?

As my understanding, there should be an oxidation-reduction reaction: $$ \ce{2 Fe^3+ + Cu → 2Fe^2+ + Cu^2+} $$ However, I always see the process using $\ce{FeCl3}$ to etch copper, but I never ...
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1answer
41 views

Compound having highest standard reduction potential

Which compound has highest SRP (standard reduction potential) value, e.g. the strongest oxidising agent? In most tables $\ce{F2}$ is at top with $E^\circ = \pu{2.87 V}$, but I've found a table listing ...
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1answer
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Oxidation of acetone using SeO2

I was trying to look-up the mechanism of reaction of organic compounds with SeO2, but I am not able to understand it. I would really appreciate if someone can predict the end product with the ...
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Why do NaNO3 + Al + NaOH yield ammonia?

From Russian test problem 4301: $$\ce{3NaNO3 + 8Al + 5NaOH + 18H2O -> 8Na[Al(OH)4] + 3NH3(g)}$$ How does ammonia evolve here? Is it that we get hydrogen gas evolving in the reaction between Al ...
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Copper Mirror Reaction

I would like to create a copper mirror on a plate of sandblasted glass. I know that a reaction exists: $$\ce{CuSO4 + N2H2 -> Cu + N2 + H2SO4}$$ I know that such a plate of copper is very weak. ...
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Why is the reaction of calcium oxide with sulfur dioxide to form calcium sulfite not a combination redox reaction?

I understand that a combination reaction is one where two substances combine to form a third substance, like with $$\ce{2Na + Cl2 -> 2NaCl}.$$ I do not understand why $$\ce{CaO + SO2 -> CaSO3}$...
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1answer
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Can an iodine clock reaction work without using a strong acid?

I'm going to do an iodine clock reaction for a project and we had to submit the materials and safety sheets for the experiment a while ago. I thought I could do one by using hydrogen peroxide, sodium ...
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What does [O] denote in organic redox reactions? [duplicate]

I've seen a few examples in the lectures we've been having and I wasn't able to find any sources talking about it. I think I remember a previous teacher saying it was a symbol for oxidation itself, ...
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1answer
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What exactly is a reducing equivalent and what does it do?

I've encountered this term in the context of cellular metabolism, but I can't seem to find an explanation of what a reducing equivalent is or why it is named this way. Wikipedia was not really helpful,...
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1answer
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What are good examples of questions that make college students think about chemistry concepts? [closed]

I am teaching the second semester of general chemistry at the college level. The course tends to get bogged down in calculations, and sometimes we forget about the big picture and what is going on at ...
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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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Standard electrode potential

What is meant by the following: Electrode potential for $\ce{M^3+/M}$ Is it standard oxidation potential (SOP) or reduction potential (SRP)? What does a high positive or negative value for SRP and ...
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3answers
3k views

How can chlorine have an oxidation number of 3 in chlorite?

I am studying redox reactions right now and I'm a bit confused about something: $\ce{ClO2^-}$ is a compound ion and in a compound ion the sum of oxidation state of participating ions has to be equal ...
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1answer
102 views

Oxidation of sodium thiosulfate by iodine

When $\ce{Na2S2O3}$ reacts with $\ce{I2}$, it undergoes a redox reaction as $$\ce{2 Na2S2O3 + I2 -> Na2S4O6 + 2 NaI}$$ Sulfur is being oxidized from a $+2$ state to a $+2.5$ state. Why isn't it ...
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Mechanisms of Birch and Bouveault-Blanc Reductions

The question is all about the sequence of a possible Birch- and Bouvault-Blanc-Reduction in this exemplary substrate. With which reduction the mechanism begin? My first attempt was to classify the ...
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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 ...