AP Chemistry Flashcards: Elementary Reactions
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Review key ideas with interactive flashcards. This set includes 10 cards to help you master important concepts.
Why is it possible to determine the rate law of an elementary reaction directly from its chemical equation?
This is possible because the stoichiometry of an elementary reaction represents the actual number of particles participating in a single collision event.
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Why is it possible to determine the rate law of an elementary reaction directly from its chemical equation?
This is possible because the stoichiometry of an elementary reaction represents the actual number of particles participating in a single collision event.
Elementary Reaction Rate Law
A rate law expression that can be inferred from the stoichiometry of the particles participating in a single reaction step (collision).
How would you represent the rate law for an elementary reaction where 2 particles of reactant A collide to form products?
You would represent the rate law using the stoichiometry, making the reaction second order with respect to reactant A.
What is the relationship between the rate law and the stoichiometry for an elementary reaction?
The rate law of an elementary reaction can be inferred directly from the stoichiometry of the particles participating in the collision.
Termolecular Collision
A simultaneous collision of three particles, which is a rare event in elementary reactions.
What fundamental aspect of an elementary reaction allows its rate law to be inferred from stoichiometry?
An elementary reaction describes a single molecular collision, so its stoichiometry directly reflects the particles involved in that one event.
Given an elementary reaction, what is the primary information used to write its rate law?
The stoichiometry of the reactants is used, as the coefficients of the reactants directly become the orders in the rate law expression.
What type of elementary reaction is considered rare?
Elementary reactions that involve the simultaneous collision of three or more particles are considered rare.
For the elementary step A + B → C, how is the rate law expression determined?
The rate law is inferred from the stoichiometry, making the reaction first order in A and first order in B.
Why are elementary reactions involving three or more particles uncommon?
They are uncommon because the probability of three or more particles colliding simultaneously with the correct orientation and energy is very low.