Adsorption is the phenomenon of attracting and retaining the molecules of a substance on the surface of a solid resulting into a higher concentration on the surface than in the bulk. The substance adsorbed is known as adsorbate and the substance on which adsorption takes place is called adsorbent. In physisorption adsorbate is held to the adsorbent by weak van der Waals forces and in chemisorption by strong chemical bond.
In the given reaction, catalyst used is
\(2H_2(g) + O_2(g) \longrightarrow 2H_2O (l)\)
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Pt
In heterogeneous catalysis the reactants are gases and the catalyst is a solid; the gases are adsorbed on the catalyst surface, where their bonds are weakened and the reaction becomes fast. Hydrogen and oxygen do not react at room temperature, but on a platinum surface they combine to form water:
\( \ce{2H2(g) + O2(g)} \xrightarrow{\ce{Pt(s)}} \ce{2H2O(l)} \)
NCERT (Pre-rationalised edition, 2022-23):
Important Features of Solid Catalysts – “(a) Activity: The activity of a catalyst depends upon the strength of chemisorption to a large extent. The reactants must get adsorbed reasonably strongly on to the catalyst to become active. …”
\( \ce{2H2(g) + O2(g)} \xrightarrow{\ce{Pt}} \ce{2H2O(l)} \)