The number of correct statements about modern adsorption theory of heterogeneous catalysis from the following is _______
A. The catalyst is diffused over the surface of reactants.
B. Reactants are adsorbed on the surface of the catalyst.
C. Occurrence of chemical reaction on the catalyst's surface through formation of an intermediate.
D. It is a combination of intermediate compound formation theory and the old adsorption theory.
E. It explains the action of the catalyst as well as those of catalytic promoters and poisons.

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• A. Incorrect: The reactants diffuse over the surface of the catalyst, not the other way around.
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• B. Correct: Reactant molecules approach and get adsorbed onto the active sites on the catalyst's surface.
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• C. Correct: Adsorbed reactants react chemically on the surface to form an activated intermediate complex.
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• D. Correct: Modern adsorption theory is explicitly a combination of the old adsorption theory (surface concentration) and the intermediate compound formation theory.
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• E. Incorrect: While it explains basic catalysis and catalytic poisons (by blocking active sites), this theory cannot fully explain the mechanism of catalytic promoters (which alter the lattice structure or increase surface area).

Conclusion

The correct statements are B, C, and D.

The total number of correct statements is 3.

Correct Answer: 3