What is a Catalyst? | Best Chemistry Review

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Catalysts


Catalysts are substances that speed up the rate of a chemical reaction, without being consumed in the process. The way a catalyst works is first, by lowering activation energy. It lowers the activation energy that is required for a chemical reaction to proceed.


By lowering that activation energy, the chemical reaction can proceed more easily. Another way that a catalyst meets it’s objective is by providing a surface for molecules to come together and to bind.


To provide a service for molecules to come together to bind is faster than just random collisions of reactive molecules. That is how a catalyst meets it’s goal of speeding up the rate of a chemical reaction. We can classify catalysts as homogeneous catalyst and heterogeneous catalyst.


A homogeneous catalyst is in the same phase as the reactants. Say you have a liquid reactant and you have a liquid catalyst, then it’s a homogeneous catalyst. A heterogeneous catalyst is just the opposite of that.


The catalyst is in a different phase than the reactants are. Some examples of this would be, take liquid bromine for example, and it speeds up the breakdown of liquid hydrogen peroxide into liquid water and oxygen gas.


You have liquid bromine and you have liquid hydrogen peroxide, those are in the same phase, that’s a homogeneous catalyst. Take, for example, the combination of ethylene and hydrogen gases to make ethane gas.


It’s catalyzed by adding powdered nickel. You have powdered nickel which is in solid form, and everything else is in gas form, or the gas phase. In that reaction, nickel is a heterogeneous catalyst. An important point to remember is that catalyst are substances that speed up the rate of a chemical reaction, without being consumed in the process.



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Last updated: 10/18/2018

 

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