what is catalyst?

Answer 1

In chemistry, a catalyst (Greek: καταλύτης, catalytēs) is a substance that decreases the activation energy of a chemical reaction (see also catalysis) without itself being changed at the end of the chemical reaction. Catalysts participate in reactions but are neither reactants nor products of the reaction they catalyse (a strange 'exception' is the process of autocatalysis). They work by providing an alternative pathway for the reaction to occur, thus reducing the activation energy and increasing the reaction rate. More generally, one may at times call anything that accelerates a reaction, without itself being consumed or changed, a "catalyst" (for example, a "catalyst for political change").

A promoter is an accelerator of catalysis, but not a catalyst by itself. An inhibitor inhibits the working of a catalyst.



Definitions
Catalysts generally react with one or more reactants to form a chemical intermediate that subsequently reacts to form the final reaction product, in the process regenerating the catalyst. The following is a typical reaction scheme, where C represents the catalyst, A and B are reactants, D is the product of the reaction of A and B:

A + C → AC (1)









B + AC → ABC (2)
ABC → CD (3)
CD → C + D (4)
Although the catalyst (C) is consumed by reaction 1, it is subsequently produced by reaction 4, so for the overall reaction:

A + B + C → D + C
the catalyst is neither consumed nor produced.

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Catalysts and reaction energetics

Generic graph showing the effect of a catalyst in an hypothetical exothermic chemical reaction. Notice that the catalysed (red) pathway, despite having a lower activation energy, produces the same final result.Catalysts work by providing an (alternative) mechanism involving a different transition state and lower activation energy. The effect of this is that more molecular collisions have the energy needed to reach the transition state. Hence, catalysts can perform reactions that, albeit thermodynamically feasible, would not run without the presence of a catalyst, or perform them much faster, more specific, or at lower temperatures. This can be observed on a Boltzmann distribution and energy profile diagram. This means that catalysts reduce the amount of energy needed to start a chemical reaction.

Catalysts cannot make energetically unfavorable reactions possible — they have no effect on the chemical equilibrium of a reaction because the rate of both the forward and the reverse reaction are equally affected (see also thermodynamics). The net free energy change of a reaction is the same whether a catalyst is used or not; the catalyst just makes it easier to activate.

The SI derived unit for measuring the catalytic activity of a catalyst is the katal, which is moles per second. The degree of activity of a catalyst can also be described by the turn over number or TON and the catalytic efficiency by the turn over frequency (TOF). The biochemical equivalent is the enzyme unit.

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Types of catalysts
Catalysts can be either heterogeneous or homogeneous. Biocatalysis is often seen as a separate group.

Heterogeneous catalysts are present in different phases from the reactants (for example, a solid catalyst in a liquid reaction mixture), whereas homogeneous catalysts are in the same phase (for example, a dissolved catalyst in a liquid reaction mixture



reff:http://en.wikipedia.org/wiki/Catalyst

Answer 2

In chemistry, a catalyst (Greek: καταλύτης, catalytēs) is a substance that decreases the activation energy of a chemical reaction (see also catalysis) without itself being changed at the end of the chemical reaction. Catalysts participate in reactions but are neither reactants nor products of the reaction they catalyse (a strange 'exception' is the process of autocatalysis). They work by providing an alternative pathway for the reaction to occur, thus reducing the activation energy and increasing the reaction rate. More generally, one may at times call anything that accelerates a reaction, without itself being consumed or changed, a "catalyst" (for example, a "catalyst for political change").

A promoter is an accelerator of catalysis, but not a catalyst by itself. An inhibitor inhibits the working of a catalyst.

You could get more information from the link below...

Answer 3

Catalyst is a chemical substance to speedup the process and after the process the catalyst will be in the same condition.

Answer 4

a catalyst speeds up chemical reaction

Answer 5

Make fastening reaction, for example:

In hydrogen purification, we should remove CO
Then we should install reactor, with Nickel Catalist
CO + 3 H2 --> CH4 + H2O

In Ethylene purification, we should remove Acetylene (C2H2)
Then we should install reactor with palladium catalist
C2H2 + H2 --> C2H4

Usually the catalyst made from metal (high grade, expensive)
ea. Palladium, Gold, Silver, etc

Answer 6

Chemically, it's something that allows a chemical reaction to take place or speeds it up significantly but is not part of the reaction.

In other terms, it's something that sets off an event or makes it escalate.

Both definitions are about the same...

Answer 7

a catalyst i s something which alters the speed of the reaction but itself reains unchanged.

Answer 8

something that produces a reaction. e.g. Petrol and an ignition source are catalysts that produce fire

Answer 9

From my own journey, i could say that prepared faith is a catalyst to spirituality. i think that for me, spirituality without prepared faith is apt to bypass unfastened and do issues unsanctioned by utilising society. prepared faith is a ballast for my pursuit of spirituality: it keeps me grounded in conceptual certainty. of direction, your consequences could selection :-)

Answer 10

a catalys is a substance that changes the rate of a chemical reaction, to give some product but , it self reamains unchanged.