Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

0
votes
2answers
33 views

The equivalent weight of HNO3 in the following reaction [on hold]

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 ...
0
votes
1answer
34 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 ...
4
votes
1answer
77 views

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 ...
3
votes
1answer
3k 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. ...
3
votes
1answer
95 views

Pourbaix diagram and the order of the species

Figure 1. Pourbaix diagram of iron (Source) The line between $\ce{Fe}$ and $\ce{Fe^2+}$ is there because the potential $\ce{Fe/Fe^2+}$ is $\pu{-0.44 V}$. The same applies for $\ce{Fe^2+/Fe^3+}$ with $...
16
votes
5answers
34k views

Painting metal, does it matter if all rust is removed before?

In the context of automobile repair work, assume a metal surface has rust over it. Does it matter if all of the rust is removed before the metal surface is painted? If it does matter, then why? It ...
0
votes
2answers
162 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?
3
votes
3answers
84 views

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?
4
votes
1answer
182 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 ...
14
votes
7answers
54k views

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 (Source (WBM)). (The figure text is quoted as well for the ...
1
vote
1answer
189 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 ...
4
votes
0answers
474 views

Cobalt Oxalate / Potassium Permanganate Titration

My class just did a lab today where we mixed cobalt oxalate with $40~\mathrm{mL}$ of $\ce{H2SO4}$ and then titrated it with $\ce{KMnO4}$ (potassium permanganate). I need the mole ratio of cobalt ...
3
votes
1answer
161 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}) & (...
3
votes
3answers
638 views

Why can wood burn all the way to charcoal instead of just creating a passivating charcoal layer?

I know burning to charcoal is actually incomplete combustion because charcoal can also burn. When a strike anywhere match burns, it burns all the way to charcoal but the charcoal doesn't further burn. ...
4
votes
3answers
28k views

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 ...
1
vote
1answer
31 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 ...
2
votes
2answers
224 views

What happens to iron electrodes (attached to a battery) in copper(II) sulphate solution?

After a few hours, the following observations were made: The solution turns green. My guess: $\ce{FeSO4}$ is formed. There are reddish-brown and black powder deposits on both the electrodes. The ...
2
votes
0answers
131 views

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 ...
1
vote
3answers
58 views

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 ...
19
votes
4answers
56k views

Why is salt needed when using vinegar to clean pennies?

Let's say you have a solution that is vinegar and it has salt (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 looking ...
5
votes
2answers
162 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 ...
-1
votes
1answer
41 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 ...
-2
votes
4answers
87 views

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. ...
0
votes
3answers
67 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. ...
2
votes
1answer
40 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 -> ...
0
votes
1answer
36 views

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 ...
2
votes
2answers
286 views

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 ...
0
votes
1answer
44 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 ...
0
votes
0answers
32 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 ...
2
votes
2answers
34 views

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 ...
3
votes
3answers
146 views

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{...
-1
votes
0answers
31 views

Why do oxidation states of N between 1 and 4 disproportionate in acidic medium?

To quote text from a standard book: In the case of nitrogen, all oxidation states from +1 to +4 tend to disproportionate in acid solution. For example, $$\ce{3HNO2 -> HNO3 + H2O + 2NO}$$ ...
15
votes
4answers
7k views

How could I cause metal to rust rapidly?

I'm writing a novel set in the mid-nineteenth century. One of my characters needs to cause an iron padlock to rust rapidly, ideally within a matter of hours. The lock doesn't need to rust away ...
0
votes
1answer
39 views

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 ...
0
votes
1answer
11k views

How to balance the reaction equation of potassium permanganate, calcium oxalate, and sulfuric acid step by step?

I have been desperately trying to balance the following equation, and finally (ultima ratio) used an online program to get it done (posted the same question there as well). $$\ce{KMnO4 + CaC2O4 + ...
12
votes
2answers
4k views

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, ...
4
votes
3answers
22k views

When does hydrogen peroxide act as a reducing and when as an oxidising agent? [closed]

My chemistry books details out both, the oxidizing and reducing properties of hydrogen peroxide, $\ce{H2O2}$. Its reducing properties: It reduces $\ce{Cl}$ to $\ce{HCl}$ It reduces $\...
1
vote
1answer
2k views

Hydrogen gas' reducing property

I just went though a reaction wherein hydrogen gas is liberated and hence restricts the product formed to ferrous and not ferric salt. I just want to know how H2 gas gets its reducing property? It has ...
3
votes
1answer
390 views

How does vinegar get rust off these coins

As experiment I found some really nasty rusty coins on the street. They were green. After looking on a website I found vinegar could eliminate the rust. It worked pretty well. I know this is a redox ...
5
votes
2answers
2k views

How to determine the potential of a cadmium zinc cell under standard conditions?

I write the half-equations: \begin{align} \ce{Zn &<=> Zn^2+ + 2e^-}& E^\circ &= +0.763~\pu{V}\\ \ce{Cd^2+ + 2e- &<=> Cd}& E^\circ &= +0.403~\pu{V} \end{align} In ...
4
votes
1answer
2k views

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 ...
0
votes
1answer
99 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 ...
4
votes
0answers
5k views

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 ...
0
votes
1answer
210 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{ **...
0
votes
3answers
6k views

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?
3
votes
0answers
71 views

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. $$\ce{X + 2 e^- ->[$k_1$] X^{2-}} \tag{1}$$ ...
1
vote
1answer
540 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 + ...
0
votes
1answer
38 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 ...
1
vote
2answers
92 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 ...
2
votes
0answers
26 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 ...