The number of reactions among the following, as written, could describe elementary reaction, is
(i) Cl2 + CO → COCl2; r = K[Cl2]^3/2[CO]
(ii) PCl3 + Cl2 → PCl5; r = K[PCl3][Cl2]
(iii) 2NO + H

Question

The number of reactions among the following, as written, could describe elementary reaction, is
(i) Cl2 + CO → COCl2; r = K[Cl2]^3/2[CO]
(ii) PCl3 + Cl2 → PCl5; r = K[PCl3][Cl2]
(iii) 2NO + H2 → N2O + H2O; r = K[NO][H2]
(iv) 2NO + O2 → 2NO2; r = K[NO]^2[O2]
(v) NO + O3 → NO2 + O2; r = K[NO][O3]

Prashant Kotian · Accepted Answer

Correct answer: 3. For an elementary reaction, the order of the reaction with respect to each reactant must exactly match its stoichiometric coefficient in the balanced equation. Reactions (ii), (iv), and (v) follow this rule. Reaction (i) has fractional order, and reaction (iii) has an order (1 for NO) that doesn't match its coefficient (2). Thus, there are 3 elementary reactions. Therefore, correct answer is 3.

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