In the Van't Hoff differential method to determine the order of a reaction, the initial rates and ar — Chemical Kinetics Chemistry Question
Question
In the Van't Hoff differential method to determine the order of a reaction, the initial rates $r_1$ and $r_2$ are precisely measured at two different initial concentrations $c_1$ and $c_2$. The order of the reaction $n$ is correctly given by which mathematical formula?
💡 Solution & Explanation
According to the rate law, $r = k c^n$. Therefore, $\log r = \log k + n \log c$. For two different concentrations, $\log r_1 = \log k + n \log c_1$ and $\log r_2 = \log k + n \log c_2$. Subtracting the two equations gives $\log r_1 - \log r_2 = n(\log c_1 - \log c_2)$. Rearranging yields $n = \frac{\log(r_1/r_2)}{\log(c_1/c_2)}$.