Sulfur dioxide is oxidized to sulfur trioxide in the following sequence of reactions: 2 SO2(g) + 2 NO2(g) → 2 SO3(g) + 2 NO(g) 2 NO(g) + O2(g) → 2 NO2(g). (b) Identify any molecule that acts as a catalyst or intermediate in this reaction.

A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It works by providing an alternative reaction pathway with a lower activation energy. In the context of the given reactions, identifying a catalyst involves recognizing any species that facilitates the conversion of reactants to products without undergoing permanent change.

An intermediate is a species that is formed during the reaction and is consumed in subsequent steps. It exists only transiently and is not present in the overall balanced equation. In the provided reactions, identifying intermediates requires analyzing the sequence to find any molecules that appear in one step and are used up in another.

A reaction mechanism is a detailed description of the steps involved in a chemical reaction, including the sequence of elementary reactions. Understanding the mechanism helps in identifying catalysts and intermediates, as it outlines how reactants are transformed into products. In this case, analyzing the two given reactions will reveal the roles of various molecules throughout the process.