Questions tagged [catalysis]

This tag is appropriate for reactions, their mechanisms, their kinetics, when catalysts of any kind are involved.

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11
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2answers
11k views

Reaction intermediates of MnO2 catalyzed H2O2 decomposition reaction

Manganese dioxide catalyzes the decomposition of hydrogen peroxide to water and oxygen gas. But what are the intermediates in this catalyzed reaction?
13
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1answer
405 views

Is it possible to make an anticatalyst?

I'm wondering if it is possible, theoretically, to create compounds which perform the opposite function of a catalyst (thus an anticatalyst). That is to say, could a compound be made which raises the ...
23
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4answers
15k views

Platinum group metals: Why are platinum and palladium great catalysts and not the others?

Platinum and palladium are great catalysts. At the same time, other metals of the so-called platinum group metals are not. What are the atomic level reasons for this?
5
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2answers
13k views

Why is platinum used as a catalyst in fuel cell electrodes (and elsewhere)?

I have rather basic knowledge of chemistry (at the level of a first year college class). But maybe somebody can still clarify with some simple words: What makes platinum a good catalyst for the ...
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2answers
807 views

Do catalysts shift equilibrium constant towards 1?

I want to be able to understand shifts in equilibrium from the maxwell boltzmann distribution. One thing I cannot get my head around is the effect of catalysts on the equilibrium position - supposedly ...
23
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3answers
528 views

Energy-efficiency aside, what are the chemical constraints on CO₂ capture and methanation?

Synthesising $\ce {CH4}$ from air and water (in a non-biological process) has been proposed as one form of energy storage. What are the chemical constraints at play here? That is to say, what sort of ...
8
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1answer
13k views

Isomerisation of alkanes under Lewis acidic conditions

My textbook says: n-Alkanes on heating in the presence of anhydrous aluminium chloride and hydrogen chloride gas isomerise to branched chain alkanes. But no mechanism is given. After a little ...
5
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2answers
34k views

Hydrogenation stereochemistry-Pd,Pt, Ni catalysts

When my textbook talks about hydrogenation using Pt, Pd or Ni heterogeneous catalysts, it never mentions if it is anti or syn addition. It simply jumps on to say that for alkynes, NiB2 (P-2) catalysts ...
13
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3answers
2k views

A misunderstanding about the energy profile of reactions with a catalyst involved

All of us are aware of the importance of the catalysts in bio-chemistry. For a high school learner like me, catalysts ,and therefore, enzymes play a bridge-like role that connect high school bio to ...
9
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2answers
8k views

How can a catalyst not be included in a rate equation if, by definition, it speeds up a chemical reaction?

I thought that anything not in a rate equation was automatically zeroth order and therefore did not affect the reaction. However, I have heard that catalysts can be involved in a reaction while not ...
7
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2answers
10k views

Demonstrating decomposition of hydrogen peroxide using iron(III) nitrate catalyst

I need a way to prove/show that hydrogen peroxide was decomposed through use of catalyst. I want to ensure that my catalyst: $\ce{Fe(NO3)3}$ or iron(III) nitrate is a catalyst, not a reactant/ ...
7
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1answer
126 views

Multiple "/" in catalysts

What does it mean if a catalyst has multiple "/" symbols, such as $\ce{Mn/Fe/Al2O3}$? Does it mean either $\ce{Mn}$ or $\ce{Fe}$, or does it mean both are supported on $\ce{Al2O3}$?
15
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3answers
937 views

Won't the net effect of a catalyst be zero if it creates a new path with lower activation energy?

A catalyst will provide a new path with a lower activation energy (Figure 1). Won't this mean the forward and backward reactions will both speed up (as they both have a lower activation energy path to ...
28
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1answer
613 views

How does Palladium dissociate H₂ so easily?

If I understand correctly, $\ce{H2}$ in the presence of $\ce{Pd}$ readily dissociates as it dissolves into the metal. With the dissociation energy for the $\ce{H—H}$ bond being so large, how is this ...
15
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2answers
7k views

Difference between Lindlar and Rosenmund catalysts

Is there any difference between the Lindlar and Rosenmund catalysts? I've checked around, and it seems the same compounds are used to make both. Is there a difference in their reactivities or are they ...
17
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1answer
658 views

What is the chemistry behind this "petrol from air" technology?

A recent news report in the UK claimed a breakthrough in making a petrol equivalent from carbon dioxide and water: A small British company has produced the first "petrol from air" using a ...
12
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4answers
11k views

Is there a catalyst that will reduce an alcohol to an alkane?

There are many reduction methods of going from an alcohol to an alkane: http://www.transtutors.com/chemistry-homework-help/hydrocarbons/reduction-of-alcohols.aspx And there are catalytic methods of ...
12
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1answer
307 views

What might serve as an initial starting photocatalyst for this large water-splitting solar simulator?

Question: What might serve as an initial starting photocatalyst for this large water-splitting solar simulator? Surely there must have been some planned experiments! The Gizmodo article Insane Light ...
4
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3answers
3k views

Which has higher rate of hydrogenation - methyl propene or trans-2-butene?

Which has higher rate of hydrogenation- methyl propene or trans-2-butene? I know that cis-2-butene has a higher rate of hydrogenation than both of these due to steric reasons, but here, both of these ...
7
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2answers
7k views

Why are hydrogenation reactions exothermic?

I learned that all reactions that yield hydrogen are endothermic (such has reforming) and reactions that use up hydrogen are exothermic (FCC cracking, hydrogenation, etc.). But why is this so? I know ...
5
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2answers
3k views

Rate of catalytic hydrogenation of alkenes

What does the rate of catalytic hydrogenation of alkenes depend upon? What'd be the increasing order of rate towards catalytic hydrogenation of the following alkenes, A (2-methylpropene), B (cis-but-2-...
4
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1answer
7k views

What are the roles of pyridine and DCM in the acylation of an alcohol?

What role does pyridine and $\ce{CH2Cl2}$ play in this reaction? (Prior to this step, the corresponding carboxylic acid was converted to the acyl chloride using DMF, oxalyl chloride, and DCM.) This ...
3
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1answer
215 views

Catalyst discovery

How are catalysts for chemical reactions found? Given a hoped for reaction, let's take the hydrogenation of carbon monoxide to methanol as an example, do chemists: Proceed directly from some ...
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0answers
223 views

How are catalysts discovered for a particular reaction? [duplicate]

I want to understand how are catalysts discovered for a particular chemical reactions say for example $\ce{Fe,~Mo}$ for Haber's Process reaction of $\ce{N2}$ & $\ce{H2}$. Reactions as examples ...
4
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1answer
100 views

What is the rate expression for decomposition of $\ce{H2O2}$ in the presence of a catalyst?

What is the rate expression for decomposition of $\ce{H2O2}$ in the presence of a catalyst? As far as I know for catalase, it is like this: $$\ce{Rate = k[H2O2][Catalase]}$$ I don't know what it is ...
2
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2answers
237 views

Dependence of the rate of a catalysed reaction on substrate concentration?

In my answer to this question: Master equation for catalyst and substrate binding?. I made the assumption along the following lines: If we have a substrate concentration $[S]$ then the rate of ...
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1answer
1k views

Why can sulfur act like a catalyst?

In the reaction of combustion of gunpowder, Sulfur is used to speed up the reaction and acts like a catalyst in that it increases the rate of reaction. However, unlike a catalyst, it is used up in ...
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0answers
82 views

What chemicals could be added to human urine to cause harmful chemicals to precipite out?

What chemicals could be added to human urine to render it drinkable with no harmful side effects? Urine is salty and contains other dissolved solids. Thus, drinking untreated urine would result in ...
0
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1answer
247 views

Catalytic energy profiles (is this Wikipedia image misleading?) [duplicate]

I am looking at the image below from the Wikipedia page for energy profiles in chemistry. I do not understand why the "$E_a$ (with catalyst)" is labeled as it is. I would argue that is not the ...
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1answer
1k views

How do catalysts provide alternative routes for reactions?

According to collision theory, a reaction will take place between, say, two molecules, if the collision between the atoms has a sufficiently high kinetic energy (to meet the activation energy ...
0
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2answers
9k views

Hydrogen peroxide: catalyst changes colour during peroxide decomposition

When adding iron(III) chloride to hydrogen peroxide, the hydrogen peroxide decomposes. Iron(III) chloride is a catalyst. But when it is first added, it changes its colour to dark brown, then near ...