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How can traces of water vapour speed up reactions between gases?
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catalysis
Nanoparticles of a gold-palladium (yellow-blue) alloy supported on acid-treated carbon (gray) directly catalyzing hydrogen peroxide formation from hydrogen (white) and oxygen (red) while shutting off unwanted hydrogen peroxide decomposition.
Traces of water vapour can act as a catalyst for certain gas-phase reactions, effectively increasing their reaction rate. A notable example is the interaction between carbon monoxide and oxygen, which proceeds only very slowly under dry conditions but is accelerated by the presence of water vapour.1
In the context of homogeneous catalysis, where the catalyst and reactants exist in the same state of matter, the water vapour facilitates the chemical process, allowing the reaction to occur more readily than it would in its absence.1