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Surface Chemistry — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistrySurface Chemistry2 Marks
Question
Give an example where physisorption changes to chemisorption with rise in temperature. Explain the reason for change.
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Answer

The process of physisorption, for example that of $H_2$ on finely divided nickel, involves weak van der Waal's forces. With increase in temperature, hydrogen molecules dissociate into hydrogen atoms which are held on the surface by chemisorption.

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