In an addition reaction, two or more molecules come together to form a single product, for example,
C₂H₂ + 2Cl₂ ⟶ C₂H₂Cl₄
This reaction consists of two successive additions. The product of the first reaction becomes a reactant and adds a second molecule of Cl₂ to form C₂H₂Cl₄
As you know, the rate of a first-order reaction depends linearly on the concentration of a single reactant. The rate of a first-order reaction that takes the form
