---
title: "Reaction Order — AP Chem Definition & Exam Guide"
description: "Reaction order is the exponent on a reactant's concentration in the rate law, found from experiment. Master it for AP Chem Unit 5 rate law and graph questions."
canonical: "https://fiveable.me/ap-chem/key-terms/reaction-order"
type: "key-term"
subject: "AP Chemistry"
---

# Reaction Order — AP Chem Definition & Exam Guide

## Definition

Reaction order refers to how much changing the concentration of one reactant affects the overall rate at which products are formed.

## Related Study Guides

- [5.3 Concentration Changes Over Time](/ap-chem/unit-5/concentration-changes-over-time/study-guide/Owtcz3zbxFZXsPI7YfwJ)
- [9.4 Thermodynamic and Kinetic Control](/ap-chem/unit-9/thermodynamic-kinetic-control/study-guide/hRZ0V3goVueXCw1JeUdA)

## Review

### Related Terms

- [First-Order Reaction](/ap-chem/key-terms/first-order-reaction): A type of reaction where its rate depends on one reactant's concentration.
- Zero-Order Reaction: A type of reaction where its rate does not depend on any reactant's concentration but remains constant.
- [Half-Life](/ap-chem/key-terms/half-life): The time required for half quantity of a substance undergoing decay to disappear.