---
title: "Second Order Reaction — AP Chem Definition & Exam Guide"
description: "A second order reaction has a rate proportional to [A]² or [A][B]. Learn how to spot it from rate data, k units (M⁻¹s⁻¹), and the linear 1/[A] plot for AP Chem."
canonical: "https://fiveable.me/ap-chem/key-terms/second-order-reaction"
type: "key-term"
subject: "AP Chemistry"
---

# Second Order Reaction — AP Chem Definition & Exam Guide

## Definition

A second order reaction is another type of chemical reaction where the rate depends on either two different reactants' concentrations or square of concentration of single reactant.

## Related Study Guides

- [5.2 Introduction to Rate Law](/ap-chem/unit-5/intro-rate-law/study-guide/oq5mJS35IadrTLHLjdqZ)

## Review

### Related Terms

- Bimolecular Reaction: This is when two molecules collide and interact in a second-order reaction. It's like our button-pressing game analogy - both players need to act together!
- [Integrated Rate Law](/ap-chem/key-terms/integrated-rate-law): For second-order reactions, this equation describes how concentration changes over time. It’s like tracking how well you and your friend improve at hitting those buttons simultaneously as time goes by.
- [Reaction Mechanism](/ap-chem/key-terms/reaction-mechanism): This term refers to the step-by-step sequence of reactions by which the overall chemical change occurs. In our game analogy, it's like understanding how hitting buttons together leads to unlocking those bonus points.