30
votes
Accepted
Won't the net effect of a catalyst be zero if it creates a new path with lower activation energy?
Your realisation is correct and something chemistry teachers try to hammer into their students’ heads time and time again (and yet, the point is still often lost):
Catalysts will never change the ...
- 67.3k
22
votes
Accepted
Difference between Lindlar and Rosenmund catalysts
This is a rather interesting question because these names actually refer to classes of reactions (specific to certain reagents and products), and aren't constrained by specific proportions of ...
- 23.9k
14
votes
Accepted
Is it possible to make an anticatalyst?
Some substances do exist that slow down reactions and they're different from catalytic inhibitors/poisons. Such substances are called negative catalysts. Here is one example I can think of right now:
$...
- 4,114
14
votes
Accepted
What is the chemical formula of KIT-6?
According to original paper (1), KIT-6 is a highly ordered cubic $Ia3d$ silica ($\ce{SiO2}$) templated by Pluronic P123 ($\ce{[EO20PO70EO20]}$) block-copolymer surfactant. As a source of $\ce{Si}$, ...
- 37.4k
13
votes
What is an example of chemical reaction that can be assisted by both an inorganic catalyst and an enzyme?
A good example is the conversion of hydrogen peroxide to oxygen and water
$$\ce{2H2O2 ->2H2O + O2}$$
It can be catalyzed by catalase, which has one of the highest known turnover numbers, or by an ...
- 20.8k
12
votes
Won't the net effect of a catalyst be zero if it creates a new path with lower activation energy?
Yes, one expects both forwards and backward reactions to speed up as you suggest; there seems to be no reason why microscopic reversibility would be suspended. The point of the catalyst will be to ...
- 30k
12
votes
What can I use as a fuel for an engine with carbon dioxide as the oxidizer?
Usually when we say something "burns", it's being oxidized. In the case of carbon dioxide only the oxygen can be oxidized, by displacing it as the element; that requires fluorine or a sufficiently ...
- 53.2k
11
votes
What is the chemical formula of KIT-6?
KIT-6 is a mesoporous silica, the chemical formula is the same for all silica which is $\ce{(SiO2)_n}$. The tridimensional structure though is usually represented as
- 1,331
11
votes
What is an example of chemical reaction that can be assisted by both an inorganic catalyst and an enzyme?
There are many many examples of reactions that are usually done in biological systems with an enzyme, but can be done outside in the lab with general acid or base catalysis.
Take for example the ...
- 5,637
9
votes
Accepted
Do catalysts shift equilibrium constant towards 1?
TL;DR Your Maxwell–Boltzmann diagram up there is not sufficient to describe the variation of rate with $E_\mathrm{a}$. Simply evaluating the shaded area alone does not reproduce the exponential part ...
- 71.1k
9
votes
Accepted
Is palladium on carbon acting as an oxidising or reducing agent?
Palladium on carbon ($\ce{Pd/C}$) is neither an oxidant nor a reductant. The reaction is the dehydrogenation of piperidine: $\ce{C5H11N -> C5H5N + 3H2}$ and here, $\ce{Pd/C}$ is merely a catalyst.
...
- 71.1k
9
votes
How do I heat my borosilicate reflux column?
That should pose no issue regarding the glass
Without images to see how unevenly you will apply the heat, I have to modify my instinctual reaction "That cannot possibly be an issue" to "Most likely ...
- 2,747
9
votes
How do I heat my borosilicate reflux column?
The first answer is great and the borosilicate glass can indeed survive harsh conditions. Here I'd like to suggest a DIY-project to improve the efficiency of the heater and make the column be warmed ...
- 37.4k
8
votes
How does a catalyst accelerate both forward/reverse reactions simultaneously?
The idea is that the activation energies is lowered for both the forward and backward reactions.
Though the activation energy for the backward reaction is higher than the activation energy for the ...
- 23.9k
8
votes
Accepted
What is an active centre of a catalyst?
The active centre is the site where the substrate binds to the catalyst in order for catalysis to take place. On a molecular level, most catalysts (or most substances really) are not just flat ...
- 15.3k
8
votes
Would singlet oxygen in the engine cause a more efficient combustion?
This hypermileage scheme is one of the more interesting ones I've come across, so I think it's worth some discussion. I don't know much at all about the engineering aspects of internal combustion ...
- 28.3k
8
votes
Accepted
Stability of transition and post-transition metal alkoxides
Alkali metal, main group, and transition metal (TM) alkoxides all have significantly different chemistry. Early- and Late-TM alkoxides also have different behaviour, so we should split this family ...
- 2,324
8
votes
Accepted
Catalysist activation energy - the Brønsted-Evans-Polanyi relation
First, a note on the Bell-Evans-Polanyi (BEP) equation:
The form you've written it in disguises what the constant $\alpha$ tells you. From the wikipedia article, it's said that $\alpha$ is a number ...
- 12.9k
8
votes
Accepted
Multiple "/" in catalysts
There should be only one "/" symbol. When more are used, it should be unambiguous from the context what is the carrier, e.g. in your case it would be more appropriate to use a dash:
$$\ce{Mn-Fe/Al2O3}...
- 37.4k
7
votes
Platinum group metals: Why are platinum and palladium great catalysts and not the others?
For those like me who weren’t sure, the platinum group metals are made up of platinum, palladium, iridium, ruthenium, rhodium and osmium.
I don’t understand where you’re getting the idea from that ...
- 67.3k
7
votes
Platinum group metals: Why are platinum and palladium great catalysts and not the others?
Platinum, palladium, and rhodium have a D-Orbital electron structure on the surface of their atoms which encourages the temporary sticking of other molecules. When other molecules stick, the overall ...
- 71
7
votes
What is role of palladium in hydrogenation reactions?
The general catalysis cycle of hydrogenation reaction is pretty simple and AFAIK well documented. It consists of for reactions, all well documented in metalloorganic chemistry.
Hydrogen activation. ...
- 21.5k
7
votes
Accepted
How exactly does the oxidation of TEMPO by NaOCl/KBr work?
I would propose the following mechanism:
Note that the oxygen radical anion isn't that bad as a leaving group as the Cl-O bond is weak. It can participate in an electron transfer with chloride anion, ...
- 14.2k
7
votes
In this specific case is the proton considered product or catalyst?
As you've illustrated with your figure from the Wikipedia article, a catalyst appears as the same compound on each side of a chemical equation. The short answer to this part of your question is that ...
- 17.4k
7
votes
Accepted
Why aren't chaperones considered catalysts?
I don’t think you are wrong. Actually molecular chaperones have been named enzymes in some texts. The molecular chaperones comprise several unrelated classes of proteins that have rather different ...
- 5,084
7
votes
What is an example of chemical reaction that can be assisted by both an inorganic catalyst and an enzyme?
Sucrose inversion (hydrolysis of sucrose into fructose and glucose).
Done with invertase — that's how human body breaks it down and that's how bees make honey.
Done with any acid at elevated ...
- 790
6
votes
Accepted
Why are hydrogenation reactions exothermic?
Let's take a look at an example of a hydrogenation reaction, namely the hydrogenation of ethene to give ethane
$$\ce{CH2\bond{=}CH2\ (g) + H2 (g)-> CH3\bond{-}CH3 (g)}$$
And now let's ...
- 168
6
votes
Reaction intermediates of MnO2 catalyzed H2O2 decomposition reaction
I am adding a more recent study to complement the answer given by tschoppi. This journal addresses the kinetics and mechanism for the decompostion of $\ce{H2O2}$ on transition metal oxide surfaces. ...
- 4,284
6
votes
Accepted
Why is the Jacobsen's catalyst with tert-Butyl groups a better catalyst for epoxidation?
This type of oxygen transfer reaction consists of a two step
catalytic cycle, wherein, first an intermediate (salen)$\ce{Mn^V}$ oxo complex is generated, and then the activated oxygen is added to the ...
- 8,465
Only top scored, non community-wiki answers of a minimum length are eligible