Cho phản ứng xảy ra trong pha khí sau:
H2 + Cl2 → 2HCl
Biểu thức tốc độ trung bình của phản ứng là
\(\nu=\dfrac{\Delta C_{H_2}}{\Delta t}=\dfrac{\Delta C_{Cl_2}}{\Delta t}=\dfrac{\Delta C_{HCl}}{\Delta t}\) \(v=\dfrac{\Delta C_{H_2}}{\Delta t}=\dfrac{\Delta C_{Cl_2}}{\Delta t}=\dfrac{-\Delta C_{HCl}}{\Delta t}\) \(v=\dfrac{-\Delta C_{H_2}}{\Delta t}=\dfrac{-\Delta C_{Cl_2}}{\Delta t}=\dfrac{\Delta C_{HCl}}{\Delta t}\) \(v=\dfrac{-\Delta C_{H_2}}{\Delta t}=\dfrac{-\Delta C_{Cl_2}}{\Delta t}=\dfrac{\Delta C_{HCl}}{2\Delta t}\)