Final answer:
The reaction is first-order with respect to both A and B, resulting in an overall reaction order of 2. A one-line mechanism compatible with the kinetics and stoichiometry would be a bimolecular reaction, A + B → P. The orders of the reaction are consistent with the law of mass action.
Step-by-step explanation:
The student has described a reaction where A and B react to form P, and the log of the concentration of A vs. time plots as a straight line. This indicates that the reaction is first-order with respect to A, meaning the rate at which A reacts is directly proportional to its concentration at any given time. If the concentration of A were to double, for instance, the rate of the reaction would also double.
A one-line mechanism consistent with the observed kinetics and stoichiometry would be a simple bimolecular reaction, such as A + B → P, where each collision between A and B has a chance to lead to product formation. Given that the reaction is first-order with respect to A, and knowing that the reaction rate ratio is proportional to the product of the concentrations of A and B, it is consistent to deduce that the reaction is also first-order with respect to B. Therefore, the overall reaction order is 2, which is the sum of the orders with respect to both A and B.
The concentration of B does not alter the kinetics assuming B is in vast excess (10 M compared to 0.01 M for A), which means B's concentration effectively remains constant over the course of the reaction, and thus, the reaction appears to be first-order overall—this is often termed a pseudo-first-order reaction contextually.