Chemical KineticshardMCQ SINGLE⭐ Must-Do

The thermal heterogeneous decomposition of gaseous Hydrogen Iodide () occurring specifically on the Chemical Kinetics Chemistry Question

Question

The thermal heterogeneous decomposition of gaseous Hydrogen Iodide ($HI$) occurring specifically on the solid surface of hot gold is a classical, widely tested textbook mechanism. What is the fundamental kinetic order of this specific high-pressure catalytic surface reaction?

Answer: A

💡 Solution & Explanation

At high initial pressures, the available active sites on the solid catalytic gold surface quickly become entirely saturated with $HI$ molecules. Because the physical surface can accommodate no more reactant, adding further gas mass cannot alter the decomposition rate, locking the kinetics firmly to a strictly constant Zero Order regime.

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