---
title: "Equilibrium Constant Expression — AP Chem Definition"
description: "The equilibrium constant expression is the ratio of products to reactants at equilibrium, each raised to its coefficient. Core skill for AP Chem Unit 7."
canonical: "https://fiveable.me/ap-chem/key-terms/equilibrium-constant-expression"
type: "key-term"
subject: "AP Chemistry"
---

# Equilibrium Constant Expression — AP Chem Definition

## Definition

The equilibrium constant expression is a mathematical representation that quantifies the concentrations of reactants and products at equilibrium. It expresses the ratio of product concentrations to reactant concentrations, with each concentration raised to their respective stoichiometric coefficients.

## Review

### Related Terms

- [Equilibrium Constant](/ap-chem/key-terms/equilibrium-constant): The numerical value obtained by evaluating the equilibrium constant expression at a given temperature.
- Reactant Concentration: The amount or concentration of a substance participating in a chemical reaction before it reaches equilibrium.
- Product Concentration: The amount or concentration of a substance produced as a result of a chemical reaction at equilibrium.