Why do zero-order reactions have a constant rate?

Zero-order reactions have a constant rate because their rate is independent of the concentration of the reactants.

In more detail, the rate of a reaction is the speed at which the reactants are converted into products. This rate can be influenced by several factors, including the concentration of the reactants, temperature, pressure, and the presence of a catalyst. In a zero-order reaction, the rate of the reaction is not affected by the concentration of the reactants. This means that even if the concentration of the reactants changes, the rate of the reaction remains constant.

The rate law for a zero-order reaction is expressed as Rate = k, where 'Rate' is the rate of the reaction and 'k' is the rate constant. This equation shows that the rate of the reaction is equal to the rate constant, and it does not depend on the concentration of the reactants. This is why the rate of a zero-order reaction is constant.

The concept of zero-order reactions is particularly important in the field of enzyme kinetics. Many enzymatic reactions follow zero-order kinetics, at least under certain conditions. This is because enzymes can become saturated with substrate, and once this saturation point is reached, adding more substrate does not increase the rate of the reaction.

In summary, zero-order reactions have a constant rate because the rate of the reaction is independent of the concentration of the reactants. This is expressed in the rate law for a zero-order reaction, which shows that the rate of the reaction is equal to the rate constant. This concept is particularly relevant in enzyme kinetics, where many reactions follow zero-order kinetics under certain conditions.