A student made a graph to show the chemical equilibrium position of a reaction. The student forgot to label the y-axis of the graph.

What best explains the label that the student should use on the y-axis? A. Concentration, because as the amount of product decreases, the amount of reactant increases over time.
B. Reaction rate, as the rates of forward and backward reactions become equal at equilibrium.
C. Concentration, because the amounts of reactants and products remain constant after equilibrium is reached.
D. Reaction rate, as the rate of forward reaction increases and rate of backward reaction decreases over time.

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.