1.

Decomposition of NH_(3(g)) on platinum surface at high temperature is a zero order reaction. Explain.

Answer»

Solution :(1) The decomposition of `NH_(3(G))` on platinum surface is represented as,
`2NH_(3(g))overset(1130K)UNDERSET(Pt)rarrN_(2(g))+3H_(2(g))`
(2) Since it is a heterogeneous catalysed reaction, `NH_(3)` gaseous molecules at high pressure are adsorbed on the metal surface covering the surface area.
(3) The number of `NH_(3)` molecules adsorbed is small compared to `NH_(3)` molecules in the gaseous PHASE.
(4) Only the molecules adsorbed on the surface GET decomposed. Hence the rate of the decomposition becomes independent of the concentration (pressure) of `NH_(3)`. THEREFORE the decomposition reaction is zero order.


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