Question

When the rates of a forward and reverse reaction are equal in a reversible reaction, does this mean that the concentration of the reactants are constant or does this mean that the concentrations of the reactants and products have become equal? Please clarify.

Answer 1

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Answer 2

Just means that the system is at dynamic equilibrium. It means that rate of forward reaction = rate of backward reaction, hence concentration of reactants are constant.

Answer 3

Concentrations do not change, but then need not be equal. Consider an analogy: you earn exactly as much money as you spend each month. That's dynamic equilibrium, the "foward" rate (earning) exactly equals the "reverse" rate (spending).

But does that tell you how much money you have in the bank? Nope. You could have $100 at the end of each month, but earn and spend $5,000 every month. On the other hand, you could have $100,000 at the end of each month, and earn and spend $5000.

Think of reaction rate as income, and reactant concentration as wealth. Income is not wealth, although they are connected, in that income causes wealth (if you earn more than you spend), and sometimes wealth causes income (if you spend more than you earn).