The key difference between positive and negative catalyst is that positive catalysts are substances that are capable of increasing the reaction rate, whereas negative catalysts are substances that are capable of decreasing the reaction rate.
A positive catalyst is a substance that can increase the rate of reaction without getting involved or consumed in the reaction process. A negative catalyst, on the other hand, is a substance that can decrease the rate of reaction without getting consumed during the reaction.
CONTENTS
1. Overview and Key Difference
2. What is a Positive Catalyst
3. What is a Negative Catalyst
4. Positive vs Negative Catalyst in Tabular Form
5. Summary – Positive vs Negative Catalyst
What is a Catalyst?
A catalyst is a chemical compound that can increase the rate of a reaction without itself being consumed. This compound can continue to act repeatedly in a chemical reaction. Basically, there are four types of catalysts: homogenous catalysts, heterogeneous catalysts, heterogenized homogenous catalysts, and biocatalysts.
We can also categorize them as positive and negative catalysts according to their effect on the rate of the chemical reaction.
What is a Positive Catalyst?
A positive catalyst can be described as a substance that can increase the rate of reaction without getting involved or consumed in the reaction process. These substances can increase the reaction rate or the reaction speed by lowering the chemical reaction’s activation energy. The decomposition of potassium chlorate in the presence of manganese dioxide catalyst (MnO2) is an example of this type of positive catalyst.
Figure 01: Catalysis Reaction Progress
Since positive catalysts can increase the reaction rate, they can also increase the yield of a chemical reaction. Increasing the reaction rate causes an increase of product given by the reaction per unit time.
What is a Negative Catalyst?
A negative catalyst can be described as a substance that can decrease the rate of reaction without getting consumed during the reaction. Sometimes, the chemical reactions can be retarded by the presence of foreign substances that are known as negative catalysts. An example of this type of catalyst is phosphoric acid, which acts as a negative catalyst to reduce the reaction rate of the decomposition of hydrogen peroxide. Moreover, we can say alcohols are also able to work as negative catalysts.
Moreover, negative catalysts can decrease the yield of a chemical reaction because they can decrease the reaction rate. Decreasing the reaction rate causes the reduction of the product given by the reaction per unit time.
What is the Difference Between Positive and Negative Catalyst?
Basically, there are four types of catalysts: homogenous catalysts, heterogeneous catalysts, heterogenized homogenous catalysts, and biocatalysts. However, there can be positive and negative catalysts as well, according to the catalyst’s effect on the rate of reaction. The key difference between positive and negative catalyst is that positive catalysts are substances that are capable of increasing the reaction rate, whereas negative catalysts are substances that are capable of decreasing the reaction rate. A positive catalyst works by lowering the activation energy to speed up the reaction; however, a negative catalyst cannot lower the activation energy, so the reaction rate is decreased.
The below infographic presents the differences between positive and negative catalyst in tabular form for side by side comparison.
Summary – Positive vs Negative Catalyst
We can categorize catalysts as positive and negative catalysts according to their effect on the rate of chemical reactions. The key difference between positive and negative catalyst is that positive catalysts are substances that are capable of increasing the reaction rate, whereas negative catalysts are substances that are capable of decreasing the reaction rate.
Reference:
1. “What Are (i) Positive Catalysts and (Ii) Negative Catalysts?” Topper.
Image Courtesy:
1. “Catalysis- Reaction progress” By Smokefoot – Wikimedia Commons (CC0) via Commons Wikimedia