Answer:
Concentration, because the amounts of reactants and products remain constant after equilibrium is reached.
Explanation:
The rate of reaction refers to the amount of reactants converted or products formed per unit time.
As the reaction progresses, reactions are converted into products. This continues until equilibrium is attained in a closed system.
When equilibrium is attained, the rate of forward reaction is equal to the rate of reverse reaction, hence the concentration of reactants and products in the system remain fairly constant over time.
When deducing the rate of reaction, concentration of the specie of interest is plotted on the y-axis against time on the x-axis.
