Answer: The concentration of AB is being plotted in the graph.
Explanation:
In a chemical reaction, products are formed in a course of time from the reactants.
As, the time of the reaction proceeds, the reactants form products, which means that the concentration of the reactants decreases as the reaction proceeds in the forward direction. While, the concentration of products increase as the reaction proceeds.
Reactants are written on the left side and products are written on the right side.
\(AB\rightarrow A+B+\text{heat}\)
From the given graph, concentration of the species is decreasing as the time increases. Thus, the specie is a reactant which is AB.
Thus, the concentration of AB is being plotted in the graph.
