How do reversible reactions reach equilibrium?

Reversible reactions reach equilibrium when the rates of the forward and reverse reactions become equal.

In a reversible reaction, reactants are converted into products and products are converted back into reactants. This process continues until a state of equilibrium is reached. Equilibrium in this context does not mean that the reaction has stopped, but rather that the rates of the forward and reverse reactions have become equal. This results in the concentrations of the reactants and products remaining constant over time.

The concept of equilibrium can be a bit tricky to understand because it's not about the amounts of reactants and products being equal. Instead, it's about the rates of the forward and reverse reactions being equal. Imagine a busy motorway with cars moving in both directions. If the number of cars entering the motorway is the same as the number of cars leaving, then the motorway is in a state of equilibrium. The same principle applies to reversible reactions.

The position of equilibrium can be influenced by changes in temperature, pressure, or concentration. For example, if you increase the temperature, the position of equilibrium will shift to favour the endothermic reaction (the reaction that absorbs heat). This is because the system will try to counteract the change and reduce the temperature by absorbing more heat. Similarly, if you increase the pressure, the position of equilibrium will shift to favour the reaction that produces fewer molecules of gas, as this will help to reduce the pressure.

In summary, a reversible reaction reaches equilibrium when the rates of the forward and reverse reactions become equal, resulting in constant concentrations of reactants and products. This state of equilibrium can be influenced by changes in temperature, pressure, or concentration.