Question

Reactions of which order show rate independent of concentration of reactant? Give one example.

Hint:

Zero-order: Rate $= k$ (constant). Units of $k$ are mol L$^{-1}$s$^{-1}$.

Answer 1

Step 1: Concept
The order of a reaction dictates how the rate depends on concentrations.

Step 2: Analysis
For a zero-order reaction, the rate law is: Rate $= k[A]^0 = k$ (constant). The rate is entirely independent of the concentration of the reactant. This occurs typically in heterogeneous catalysis where the catalyst surface is saturated.

Step 3: Conclusion
Zero-order reactions show rate independent of concentration. Example: Decomposition of ammonia on platinum or iron surface: $2NH_3 \xrightarrow{Pt} N_2 + 3H_2$.

Final Answer:

Zero-order reactions. Example: Decomposition of $NH_3$ on a hot platinum surface.