Question

Why is manganese dioxide (MnO2) called a positive catalyst?

A. Because it speeds up a reaction.
B. Because it slows down a reaction.
C. Because it has a negative impact on reactions.
D. Because it remains inert in reactions.

Answer 1

Manganese dioxide (MnO2) is called a positive catalyst because it speeds up a chemical reaction without being consumed, and can be used repeatedly.

Step-by-step explanation:

Manganese dioxide (MnO2) is called a positive catalyst because it significantly speeds up a chemical reaction without being consumed by the reaction itself. This substance increases the rate by providing an alternative reaction pathway with a lower activation energy. After such a reaction, manganese dioxide returns to its original state and can be used repeatedly, which fits the definition of a catalyst. In chemical notations on equations, a catalyst is indicated above the yield arrow to show its presence in the reaction without listing it as a reactant or a product.