Why does reaction rate increase with a catalyst

A catalyst is a substance which increases the rate of a chemical reaction but it is not used up remains chemically unchanged at the end.

It provides an alternative reaction pathway of lower activation energy. Only a very small amount of catalyst is needed to increase the rate of reaction between large amounts of reactants. Key is licensed under a Creative Commons Attribution 4. Skip to content Chapter To gain an understanding of collision theory. You might find that the rate of reaction is limited by the concentration of the weaker solution, and increasing the concentration of the other makes no difference.

What you need to do is fix the concentration of one of the reactants to excess. Now you can increase the concentration of the other solution to produce an increase in the rate of the reaction. How does surface area affect a chemical reaction? If one of the reactants is a solid, the surface area of the solid will affect how fast the reaction goes.

This is because the two types of molecule can only bump into each other at the liquid solid interface, i. So the larger the surface area of the solid, the faster the reaction will be. Smaller particles have a bigger surface area than larger particle for the same mass of solid. There is a simple way to visualize this. Take a loaf of bread and cut it into slices.

Each time you cut a new slice, you get an extra surface onto which you can spread butter and jam. The thinner you cut the slices, the more slices you get and so the more butter and jam you can put on them. Rates usually increase when the concentration of one or more of the reactants increases.

For example, calcium carbonate CaCO 3 deteriorates as a result of its reaction with the pollutant sulfur dioxide. The rate of this reaction depends on the amount of sulfur dioxide in the air Figure 2.

An acidic oxide, sulfur dioxide combines with water vapor in the air to produce sulfurous acid in the following reaction:. In a polluted atmosphere where the concentration of sulfur dioxide is high, calcium carbonate deteriorates more rapidly than in less polluted air.

Phosphorous burns rapidly in air, but it will burn even more rapidly if the concentration of oxygen in is higher. Watch this video to see an example. However, in the absence of these catalysts for example, in the bottle in the medicine cabinet complete decomposition can take months. A catalyst is a substance that increases the rate of a chemical reaction by lowering the activation energy without itself being consumed by the reaction. Activation energy is the minimum amount of energy required for a chemical reaction to proceed in the forward direction.

A catalyst increases the reaction rate by providing an alternative pathway or mechanism for the reaction to follow Figure 3. Catalysis will be discussed in greater detail later in this chapter as it relates to mechanisms of reactions. Chemical reactions occur when molecules collide with each other and undergo a chemical transformation. Before physically performing a reaction in a laboratory, scientists can use molecular modeling simulations to predict how the parameters discussed earlier will influence the rate of a reaction.

The rate of a chemical reaction is affected by several parameters.