NO(g) + NO3(g) → 2 NO2(g) rate = k[NO][NO3] 50. The reaction represented above occurs in a single st — Kinetics Chemistry Question

STEPS:

1. Recall the core requirements of Collision Theory: According to collision theory, for a chemical reaction to occur between reacting gas particles, they must satisfy three specific conditions:
* They must physically collide with one another.
* The colliding particles must possess a minimum threshold of kinetic energy, known as the activation energy ($E_a$), to overcome electron-electron repulsions and initiate bond rearrangement.
* The particles must collide in a particular spatial orientation (geometric alignment) so that the specific atoms that are going to form new bonds actually come into contact.
2. Analyze the parameters already accounted for in the problem: The scientist has already successfully calculated the rate of collisions between $\text{NO}$ and $\text{NO}_3$ that possess sufficient energy to overcome the activation energy. This means the first two criteria of collision theory (collision frequency and sufficient energy) have been fully integrated into their calculation.
3. Identify the missing variable causing the discrepancy: Despite having enough energy, only a small fraction of these energetic collisions actually result in a reaction. This indicates that a third constraint is filtering out the majority of these otherwise successful collisions.
4. Apply the orientation constraint (steric factor): Because $\text{NO}$ and $\text{NO}_3$ are asymmetric, multi-atom molecules, they must collide with a highly specific alignment (e.g., the nitrogen atom of $\text{NO}$ colliding directly with a specific oxygen atom of $\text{NO}_3$) for the oxygen transfer to occur. If they collide sideways, backwards, or at an unfavorable angle, they will simply bounce off one another elastically without reacting—regardless of how much kinetic energy they carry.
5. Conclude the correct option: The requirement for a particular collision orientation is the only factor that explains why the observed rate is only a small fraction of the calculated energetic collision rate, confirming Option B as the correct answer.

*

WHY_OTHERS_WRONG:

• Option A is incorrect: Bimolecular gas reactions of this type proceed via rapid, two-particle collisions. The probability of a third particle colliding at the exact instant and location of a binary collision to absorb its energy is exceedingly low, and is not a mechanism that governs or limits simple single-step bimolecular reaction rates.
• Option C is incorrect: The activation energy of a reaction is an intrinsic barrier determined by the nature of the chemical bonds being broken and formed in the transition state. It is a constant for a given reaction pathway and is entirely independent of the concentrations of the reacting particles.
• Option D is incorrect: While temperature dictates the average kinetic energy of the molecules (and therefore the fraction of collisions that can overcome the barrier), the physical height of the activation energy barrier itself does not depend on temperature. Furthermore, the scientist already accounted for the activation energy barrier and temperature in their kinetic calculations, meaning temperature cannot account for the remaining discrepancy.