1.

(a) (i) Heat of adsorption is greater for chemisorptions than physisorption. Why? (ii) Give three examples for heterogeneous catalysis.

Answer»

Solution :(a) (i) Chemisorption has higher heat of ADSORPTION, because in chemisorption the chemical bonds are much stronger. In adsorbed state the adsorbate is hold on the surface of adsorbent by attractive forces (bond). And chemisorption is irreversible one. Therefore, heat of adsorption is greater for chemisorptions than physisorption.
Chemisorption, heat of adsorption range 40-400kJ/mole.
(ii) 1. Hydrogenation of ethylene in the presence of Nickel
`underset("Ethylene")(CH_(2)) = CH_(2) + H_(2) overset(Ni)rarr underset("Ethane")(CH_(3))- CH_(3)`
2. Decomposition of `H_(2)O_(2)` with Pt catalyst
`underset("Hydrogen PEROXIDE")(2H_(2)O_(2) overset(Pt)rarr underset("WATER")(2H_(2)O)+ O_(2)`
3. Friedel crafts reaction
`underset("Benzene")(C_(6)H_(6)) + underset("Ethanoyl chloride")(CH_(3)COCl) underset(AlCl_(3))overset("Anhydrous")rarr underset("Acetosphenone")(C_(6)H_(5)COCH_(3)) + HCl`


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