Questions tagged [reaction-control]

Questions related to the chemical and physical influences that influence the rate and probability of chemical reactions. Not to be confused with [catalysis] or [reaction-mechanism].

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15 views

What are the chemical principles behind paper/ink deterioration over time and how do I prevent them? [duplicate]

I have been working on a time capsule for the past few months, in which I decided to not include any electronics (ie: no USB). I am done writing the content of the capsule, but I have some concerns ...
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1answer
18 views

Catalysts to accelerate foamy polyurethane reaction

This is the reaction that I am referring to: https://www.youtube.com/watch?v=EoRUSo0BWC0 I am interested in finding catalysts to accelerate this fun chemistry demonstration. I have heard that some ...
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22 views

Why does the reaction with copper and nitric acid change with concentration? [duplicate]

Depending on the concentration of nitric acid, copper undergoes two distinct reactions. For dilute concentrations of nitric acid, the reaction is $$3\text{Cu}+8\text{HNO}_3\rightarrow 3\text{Cu(NO}_3\...
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Role of pH in azo C-coupling reaction, continued

In the question, "What is the role of pH in azo coupling reaction of diazonium with phenol and aniline?" asked by @DhrubaBanerjee and answered by @Klaus-DieterWarzecha, I find several ends untied. I ...
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2answers
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Can equilibrium be calculated at any time of an acid base reaction and still be the same? [closed]

Should the equilibrium constant $K$ be calculated at the end of an acid-base titration or can we calculate it in the middle of the titration for example? If so, will the calculated equilibrium ...
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1answer
65 views

Why do we use Δ to mean heating?

To express heating, we usually use $\Delta$ over reaction arrows like \begin{align} \ce{CaCO3 ->[\Delta] CaO +O2}. \end{align} Why do we use $\Delta$ to mean heating during chemical reactions? I ...
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1answer
97 views

Which reaction rate formula is suited for diatomic molecules in a plasma?

I am an experimental physicist, so I unfortunately do not know much about chemistry except the basics. For my current study, I am investigating diatomic molecule formation in plasma. These diatomic ...
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69 views

Why mixture turns brown upon heating, during esterification with H2SO4?

In the lab I was synthesising an ester with sulphuric acid as a catalyst. However the mixture turned brown and my teacher said I had burnt the acid, but what does this actually mean?
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1answer
20 views

What are standard controllers for automatic pH control?

My background in control theory comes from electrical engineering (robots, motors, etc.) and I want to build a control system for automatic pH control. Can I directly apply my knowledge from ...
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1answer
130 views

When is a reaction said to be under kinetic control, is it not easily reversible?

If we consider this reaction: Compound 1 + Compound 2 --> Compound 3 I understand that if a reaction is under kinetic control, the less stable (e.g. a mono-substituted diene) is formed and if the ...
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1answer
226 views

Change of first order rate constant with temperature [closed]

In the decomposition of $\ce{N2O5}$, the time taken to reduce the concentration of $\ce{N2O5}$ half of the original amount is 12 min at $\pu{50^\circ C}$, while 5 h at $\pu{25^\circ C}$ and 10 days at ...
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Why is direct addition not preferred in this reaction? [duplicate]

According to HSAB, direct addition is more preferrable in this reaction with the hard carbonyl carbon electrophile and the hard grignard reagent. But answer given in my book is that with 1,4- addition....
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1answer
39 views

Which chemicals can counter the corrosion of tamperproof hardware encryption chips?

I'm moving from software implementations to hardware. I need to reverse engineer silicon chips, though the tech that I want to study may have a corrosive chemicals that's supposed to destroy the chip ...
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How to predict and measure excess values of reactivity ratios for copolymerization with three monomers?

I ask this question because I haven't found interesting literature on the subject and I would like to know if my way to think is good or pure bullshit. Also the question is quite long because I have ...
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2answers
315 views

What is the relationship between the constant of equilibrium (Kc) and the position of equilibrium? [duplicate]

I understand that the constant of equilibrium is a ratio of the concentration of the products to the reactants and that this value allows one to estimate whether the position of equilibrium lies to ...
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2answers
289 views

Half life of Nitrofurantoin

Both wikipedia and Toxnet list the half-life of Nitrofurantoin as 20-60 minutes in the blood plasma. Can anyone explain how this is so short, especially for an antibiotic, and how it still has time to ...
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1answer
144 views

Creating water from hydrogen and oxygen [closed]

Assuming a scientist has two canisters: One with a liter of pure gas of hydrogen (single atoms gas), and one with half a liter of pure gas of oxygen (single atoms gas). The scientist desires to ...
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64 views

Is chemical equilibrium possible at any temperature and pressure?

Consider the chemical reaction ${\rm Na+Cl\to NaCl}$ by mixing ${\rm Na}$ with ${\rm Cl}$ (or by mixing ${\rm NaOH}$ with some acid). This process is exothermic while the reverse ${\rm NaCl\to Na+Cl}$ ...
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1answer
210 views

How to explain the products of the nucleophilic aromatic substitution of 1-chloro-3-methylbenzene with NaOH?

I guess this reaction is a nucleophilic aromatic substitution where $\ce{ONa-}$ is the nucleophile $\ce{Cl-}$ the leaving group, is that right? Methyl group is a ortho-, para- director. So why should ...
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1answer
885 views

Arrhenius equation in exothermic reactions

According to the Arrhenius equation, the rate of reaction increases when the temperature increases. But according to Le Chatelier's principle, the reaction rate decreases when the temperature ...
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1answer
282 views

A chamber to control concentration of a vapor: Is there a name for this equipment?

Mechanical engineer here so please excuse me if my question seems dumb to you! I want to have a chamber $(\approx 40 \times 30 \times \pu{30 cm})$ to control concentration $(\pu{ppm})$ of a flammable ...
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1answer
4k views

What visual observations can confirm that a reactant is the limiting reagent?

I have this lab question for the lab called Copper Collection Stoichiometry, where we choose an amount of the limiting reagent (iron) for a reaction between copper (II) sulfate and iron. We are to ...
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184 views

Aza-enolates: why no reaction at N

My understanding is that aza-enolates have an advantage over enamines in enolate-type alkylations because the reaction at N is less likely. As a result, unactivated electrophiles can be used (i.e. ...
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2answers
777 views

Mechanism of Halogenation of Alkene

In the above reaction, we use a non-polar compound (such as CCl$_4$) as a solvent. Then, why does the Br$_2$ polarise on attack by the alkene, even though a non-polar solvent does not encourage ...
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Can carbocation rearrangements have kinetic and thermodynamic products? [closed]

As the figure in this webpage says, at low temperatures, the major product of hydrohalogenation of 1,3-butadiene is the kinetic product, the 1,2-addition product. At high temperatures, the major ...
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1answer
346 views

E2 Reactions in Cyclic Structures

In my textbook, the percentages of anti-eliminations are given which are quite contrary to expectations. The reason is also not given quite clearly. Why does the preference for anti-periplanarity ...
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1answer
95 views

Hydride Donating Ability [closed]

We know that some compounds can donate $\ce{H-}$ anion to attain stability. What are the conditions under which it occurs and what should be the extent of stability of the product for this pathway to ...
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2answers
631 views

Does gravity affect the rate of a chemical reaction?

For example, on planets with lower gravity, would the rate of reactions be lower because the reactants are slower to mix with one another?
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1answer
1k views

Can the summation of activation energy and reactant's initial internal energy change with temperature?

Look at the graph. The orange arrow represents the summation of activation energy and reactant's initial internal energy. Can it change with temperature? Is there any specific name for this summation?
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Aluminium etching

I'm trying to etch a very fine pitch ($\pu{0.5 mm}$) aluminium stencil for use with SMT printed circuit board making. I've done some reading on the topic and found that the safest way probably is to ...
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1answer
92 views

How to stop a lye + oil + water reaction in aluminium container?

I was making soap using a guide for the first time. I accidentally used an aluminium container. It has lye and olive oil in it and was kept on the stove; now it is bubbling and not ceasing (I've ...
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3answers
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Why do we need sulfuric acid in creating alkyl bromide and not in creating alkyl iodide from alcohol and hydrogen halide?

i) $\ce{R-CH_2-OH + HBr ->[H_2SO_4] R-CH_2-Br + H_2O}$ ii) $\ce{R-CH_2-OH + HI -> R-CH_2-I + H_2O}$ What role does sulfuric acid play in the first reaction? Why are we not using it in the ...
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2answers
188 views

Chemical oscillators that behave like a double pendulum

Oscillating chemical reactions such as BZ-reaction or chemical clock typically result in sequential systematic changes, most notable of which is arguably coloring. Though underlying mechanism can be ...
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1answer
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Formation of α,β-unsaturated ketones

In Claisen-Schmidt condensation I've used $\ce{NaOH}$ catalyst. Can I use $\ce{KOH}$ instead of $\ce{NaOH}$?
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4answers
14k views

Why should the temperature be maintained at 0–5 °C in a diazotisation?

I know that in a diazotisation reaction, the temperature should be carefully maintained within the range of 0–5 °C by use of an ice bath. Why is this so? How does the temperature affect the stability ...
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Enantiomers in anisotropic achiral chemical environments

Consider a functionalised molecular box or cage which has an electrostatic gradient due to positively charged groups one one of its faces. This environment is achiral as there are reflection ...
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1answer
2k views

Python package for modelling chemical reactions

I'm looking for a package that is compatible with Python 3 and can actually do work with reactions along with, for instance, referencing values. Ideally, it should also not be a package that will take ...
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1answer
95 views

Continuous chemical reaction network versus chemical reaction network - difference?

I'm reading a paper entitled Reachability Problems for Continuous Chemical Reaction Networks and as I was reading it I realized: I have no idea what the difference is between a continuous chemical ...
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1answer
420 views

Noyori hydrogenation and the Curtin–Hammett principle

My question is relating to how the Curtin–Hammett principle applies to homogeneous hydrogenation using chiral ligands. Figure 0: An example of a quadrant diagram used as a mnemonic to predict the ...
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157 views

Can activated charcoal retain adsorbtion properties even when submerged in liquids?

This is following a question on Skeptics Stackexchange, where apparently medical science claims that activated charcoal can adsorb poison when ingested. One of the members posted a related question on ...
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115 views

Could stabilized aqueous ozone be bottled to prevent half life/sanitization window?

Could stabilized aqueous ozone be bottled to prevent half life/sanitization window? Typically upon creating stabilized aqueous ozone, it has a shelf life and a sanitization window of 24 hours from ...
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1answer
594 views

Why is the product of the reaction between iron and steam is iron (II, III) oxide and not iron (II) oxide or iron (III) oxide? [duplicate]

The reaction between Iron and steam in my textbook is given as this: $$\ce{3Fe + 4H_2O <=> Fe_3O4 + H_2} $$ My question is why these following reactions are not possible or do not happen. $$\...
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How well will molten iron chrysolite (fayalite) react with hydrogen?

The equation balances nicely, but would the reaction tend to proceed this way? What temperature and time would be needed? $\ce{Fe2SiO4 + 2H2 -> 2H2O + 2Fe + SiO2}$ There is no problem with ...
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163 views

Will Ethanol degrade Silicone or “RTV” specifically “RTV 734”, or cause it to “leach” ingredients at temperatures below 250 degrees farenheit?

Will Ethanol degrade Silicone or "RTV" specifically RTV 734, a flowable sealant produced by Dow Corning, or cause it to "leach" ingredients at temperatures below 250 degrees Fahrenheit? Such as in ...
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3answers
97 views

Why do some reactions need to be maintained at a particular temperature for prolonged periods of time?

Some reactions require that temperatures of 70–100 °C to be maintained for periods of time as long as 24 hours. Why is this so?
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1answer
67 views

Hydration reaction

Currently I'm measuring the rate of completion of a hydration reaction by putting a temperature probe in the middle of a cup full of reagents and measuring the temperature in an isolated box. The main ...
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1answer
428 views

Equation for collision frequency of molecules/ions in aqueous solution?

There are equations that describe collision frequency in the gas phase, but I am wondering if this collision theory has been extended to describe the collisions of molecules and/or ions that are ...
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2answers
107 views

Dimethylene Cyclohexane to Octalin-1,4-Dione | Hydroboration vs. Ozonolysis Pros Cons

With regards to the following synthesis, what are some pros and cons of using hydroboration oxidation followed by oxidation of the alcohols compared to ozonolysis. More specifically, how do the two ...
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1answer
310 views

How does haloform reaction take place if the reactants NaOH and X2 react with each other?

If $\ce{NaOH}$ reacts with halogen to produce $\ce{NaX}$ and $\ce{NaXO3}$, then how does haloform reaction take place?
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3answers
770 views

Hydrogen reactions with catalysts

I have a question about reactions involving hydrogen using catalysts. I'm a layman, so forgive me if my questions seem elementary. Reacting hydrogen plus oxygen and a flame reacts, unleashing energy (...