First-order reactions

First-order reactions are chemical processes where the rate of reaction depends directly on the concentration of a single reactant. As the reactant's amount decreases, the reaction slows down proportionally. Imagine dye fading in sunlight; the faster the initial dye concentration, the faster the color disappears. Mathematically, the rate is proportional to the reactant's concentration (\(rate = k \times [reactant]\)). These reactions often follow exponential decay, meaning the amount of reactant decreases by a consistent percentage over equal time intervals. They are common in nature and industry, including radioactive decay and drug elimination from the body.