Q.Explain the rate determining step with an example.

Step 1. A multi-step reaction mechanism proceeds through a sequence of elementary steps, each with its own (usually different) rate.

Step 2. The SLOWEST of these steps acts as a bottleneck: no matter how fast the other steps are, the overall reaction cannot proceed any faster than this slowest step allows, so it 'determines' the observed overall rate -- hence rate-determining step.

Step 3. Example: the iodide-catalysed decomposition of hydrogen peroxide, $2H_2O_2(aq)\xrightarrow{I^-}2H_2O(l)+O_2(g)$, proceeds via Step 1 (slow, rate-determining): $H_2O_2+I^-\rightarrow H_2O+OI^-$, and Step 2 (fast): $H_2O_2+OI^-\rightarrow H_2O+I^-+O_2$. …

Define the rate-determining step as the slowest bottleneck step of a mechanism, then use the $H_2O_2/I^-$ two-step mechanis …

• Assuming the FIRST step written in a mechanism is automatically the rate-determining one -- it is determined by which step is …