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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 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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2answers
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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
32 views

Why does copper decrease in mass when reacted with silver nitrate?

I did a lab recently of the reaction of copper and silver nitrate. $$\ce{Cu(s) + 2AgNO_3(aq) -> Cu(NO_3)_2 + 2Ag(s)}$$ I measured the mass of copper before and after the single replacement ...
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1answer
36 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
27 views

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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0answers
22 views

Oxidation of Metals

Solid metal crystals are composed of metal cations bound to delocalised electrons whereby the metal cations exhibit a full outer shell. So why do solid metals undergo oxidation when the metal cations ...
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0answers
16 views

Oxidation of a metal by an inorganic acid [on hold]

What is the effect of particule size and temperature on the reaction of a metal and an inorganic acid? I need it for a paper that I have to hand in but I cannot find the answer anywhere and I haven't ...
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0answers
19 views

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
39 views

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
39 views

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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11 views

Will there be electrical conductivity when two platinum metal strips are connecting with hydrochloric acid? [closed]

In the following set-up, the bulb does not light up. Which of the following changes may light up the bulb? (1) Replacing platinum electrodes with silver electrodes (2) Replacing silver chloride powder ...
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1answer
71 views

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
22 views

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
24 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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0answers
48 views

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 ...
3
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1answer
160 views

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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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
41 views

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
53 views

Working principle of simple chemical cells

I have just learnt about simple chemical cells but I have no idea how to determine which cells will work and which will not and the working principle of those cells. I know that a chemical cell with $...
3
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2answers
125 views

What are the products formed when nitrogen dioxide reacts with water?

I've seen two different equations for the reaction of nitrogen dioxide with water: $$\ce{2NO2 + H2O -> H+ + NO3- + HNO2}$$ and $$\ce{3NO2 + H2O -> 2H+ + 2NO3- + NO}$$ Are both of these ...
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2answers
49 views

How to balance this redox reaction taking place in a basic medium?

How to balance this reaction which is taking place in a basic medium? $$\ce{Al + MnO4- -> MnO2 + Al(OH)4-}$$ My Attempt Reduction half reaction: $$ \begin{align} \ce{4 H+ + MnO4- + 3 e- &-&...
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1answer
69 views

Replacement for Centrifuge in Calcium Content Determination

Basically, I'm performing a lab investigation to determine calcium content in different milk sorts. Since my school didn't have any EDTA, I'm using Sodium Oxalate to form a precipitate with Calcium ...
3
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1answer
39 views

Calculating the standard reduction potential for the oxidation of water

I was working with Latimer and Frost diagrams for oxygen when I came across what seems to me a contradiction. From the Latimer diagram for oxygen below, we know the standard reduction potential for ...
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1answer
47 views

Half-Reactions of Hydroxide [closed]

The following is the equation I have: $$\ce{Ca(s) + 2H2O(l) -> Ca(OH)2 v + H2 ^}$$ I am tasked to write the half-reaction equations for both the oxidation and/or reduction process. So, currently ...
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1answer
584 views

How exactly does a battery work (specifically Pb/H2SO4/H2SO4/PbO2 lead acid battery)?

Specifically talking about the lead-acid battery, I understand (or think I understand) this much: The anode, in the presence of the electrolyte, $\ce{H2SO4}$ will be oxidised: $$\ce{Pb (s) + SO4^2- (...
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1answer
1k views

Explaining the colour change in the potassium permanganate titration of Fe2+ ions

In the redox titration: $$\ce{MnO4- + 8H+ + 5Fe^2+ -> Mn^2+ + 4H2O + 5Fe^3+}$$ the colour change which occurs is purple to colourless, because of the decreased concentration of permanganate ions. ...
2
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0answers
53 views

Abnormal reaction of grignard reagent

My book states that: When isopropyl magnesium bromide is added to diisopropyl ketone, the expected tertiary alcohol is not obtained; instead the secondary alcohol; diisopropyl carbinol is obtained ...
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2answers
112 views

Reduction of hydrogen sulfide by silver

Why can $\ce{H2S}$ be reduced by $\ce{Ag}$ when left in air: $$\ce{2 Ag + H2S -> Ag2S + H2}$$ If silver is a noble metal that should not reduce hydrogen?
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1answer
42 views

Do redox reactions always contain pure elements?

According to a video by the Organic Chemistry Tutor, a quite well-known chemistry channel on YouTube, you can easily identify a redox reaction by seeing if there are atoms in their elemental states on ...
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1answer
33 views

Does berylium gain or lose electrons?

Does beryllium want to gain or lose electrons? I know it has 4 protons, 2 valence electrons, and it will gain or lose 2 electrons, but what is it?
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5answers
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Which is anode and which is cathode?

A maybe (hopefully) simple question about the denotations of "anode" and "cathode". The below image is a schematic of a polymer solar cell from http://www.plasticphotovoltaics.org/lc/lc-...
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0answers
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Can PCl5 act as an reducing agent?

I know that in PCl5 phosphorus is in +5 state and can't go in any further state. But in a book of my coaching class they state that it can act as an reducing agent through chlorine. Is this statement ...
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1answer
99 views

Why is the conjugate of a strong oxidizing agent a weak reducing agent?

I am a grade 12 student. While I was reviewing some electrochemistry, I had the following question. Take this reduction half-reaction: $$\ce{F2 (g) + 2e- <=> 2F- (aq) + $\pu{2.87V}$}$$ I know ...
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2answers
231 views

Why won't removing the salt bridge cause the battery to recharge?

If I understand correctly, the salt bridge in a battery is used to move positive ions towards the side that is becoming more negative, and negative ions towards the side that's becoming positively ...
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0answers
32 views

Production of alkyl halides [duplicate]

One of the famous reactions of production of alkyl halides is the reaction of hydrogen halide with alcohols. The synthesis of the alkyl halide is different depending upon the halogens. I was taught ...
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1answer
149 views

How to convert micromolar concentrations into molar quantities, when the volume is also known

\begin{array}{c|cccccc} \text{Sample} & \text{Ammonia} & \text{Phosphate} & \text{Silicate} &\text{Nitrate + nitrite} & \text{Nitrite} & \text{Mn} \\ & (\pu{\mu M}) & (...
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0answers
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Can iodometry analyse the peroxide radicals of palmitic acid after it has been heated?

I know that oleic acid in palm oil forms hydroxide radicals to form aldehydes in their secondary oxidation. Does a palmitic acid go under a similar process?
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2answers
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How does copper reduce dilute nitric acid to nitric oxide and concentrated nitric acid to nitrogen dioxide?

Here are the 2 equations: \begin{align} \ce{3Cu + 2NO3- + 8H+ &<=> 3Cu^2+ + 2NO + 4H2O} & E &= 0.62~\mathrm{V}\\ \ce{3Cu + 2NO3- + 4H+ &<=> 3Cu^2+ + 2NO2 + 2H2O}& E &...
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1answer
880 views

In a galvanic cell where the two electrodes are in the same electrolyte solution, why do reduction and oxidation occur separately?

In a certain book, I was presented with the following solution: An iron nail is attached by a piece of wire to a magnesium ribbon, and the iron and magnesium are placed into the same container, with ...
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0answers
21 views

Half-reaction for ammonium nitrate comproportionation into dinitrogen monoxide.

Ammonium nitrate comproportionates into dinitrogen monoxide in the following reaction: $\ce{NH4+ (aq) + NO3- (aq) -> N2O(g) + 2H2O (l)}$ I attempted to write the half-reactions by calculating ...
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3answers
99 views

Balancing the Redox reaction by Half reactions

I'm having trouble balancing this reaction using half reactions: $$\ce{I2 + KOH -> KI + KIO3 + H2O}$$ I so far know that Iodine is reduced when it forms KI(oxidation no decreases from 0 to -1) and ...
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1answer
83 views

How to apply oxidation numbers in the reaction to form hydrogen peroxide from a superoxide?

In the following reaction: $$\ce{2O2- (aq) + 2H+ (aq) <=> H2O2 (aq) + O2(g)}$$ I see where some oxygen atoms have lost electrons, but I do not see what has gained electrons. On the reactant ...
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0answers
39 views

Why does standard reduction potential get multiplied by the change in oxidation state and not by the number of electrons transferred?

The whole basis of Frost diagrams is to have a graphical representation of the Gibbs free energy of formation ($\Delta{G}_{f}$) of different oxidation states of an element using the proportional ...
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0answers
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Manganese (II) oxidation by air

I am studying the reaction of dissolved dioxygen with manganese(II) hydroxide for the Winkler method: 2Mn(OH)2(s)+O2(aq)⟶2MnO2(s)+2H2O(l) The ...
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1answer
397 views

Why isn't hydration an oxidation reaction?

http://chemistry2.csudh.edu/rpendarvis/OxRed.html states, Addition or removal of water does not involve, by itself, an oxidation or a reduction reaction. The addition of water to an aldehyde to ...
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1answer
2k views

Is there a database which give reaction constant?

For instance, I have a chemical reaction like : $$\ce{Fe^{2+} + $0.5$O2 + H^{+} ->Fe^{3+} + $0.5$ H2O}$$ And I would like to use Action-Mass law, but I need to have equilibrium constant for this ...
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1answer
49 views

Oxidation states for covalent compounds [duplicate]

Yesterday, I came across $\ce{SO2}$ and was supposed to write the reduction and oxidation half reactions. However, I do not understand the reason why S is assigned the oxidation number of 4+. Oxygen ...
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4answers
12k views

Why is Cr(2+) a stronger reducing agent than Fe(2+) in water?

According to me, $\ce{Fe^{2+}}$ should be a better reducing agent because $\ce{Fe^2+}$ - after being oxidized - will attain a stable $\ce{d^5}$ configuration, whereas $\ce{Cr^2+}$ will attain a $\ce{d^...