alleryStart learning →Nitric oxide reacting with chlorine, 2NO + Cl2 giving 2NOCl, appears to occur as an elementary termolecular step. What rate law follows from that step?
Arate = k[NO]^2[Cl2]
Brate = k[NO][Cl2]
Crate = k[NO][Cl2]^2
Drate = k[NO]^2[Cl2]^2
Answer & Solution
Correct answer: A. rate = k[NO]^2[Cl2]
1. For an elementary reaction, and only for one, the rate law follows straight from the coefficients.
2. The step consumes two NO and one Cl2 in a single three body collision.
3. So NO enters squared and Cl2 enters to the first power: rate = k[NO]^2[Cl2].
4. The overall order is 3, matching the three colliding particles.
5. The option k[NO][Cl2] forgets that two NO molecules must both be present in the collision.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 12 "Kinetics", section 12.6 Reaction Mechanisms_
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