Equilibrium constant Calculator
Expression for equilibrium constant Kc.
Formula first
Overview
The equilibrium constant (Kc) defines the ratio of product concentrations to reactant concentrations at a state of dynamic equilibrium for a chemical system at a specific temperature. It is derived from the law of mass action, where each concentration is raised to the power of its stoichiometric coefficient from the balanced chemical equation.
Symbols
Variables
ratio = Equilibrium Ratio, K_c = Equilibrium Constant
Apply it well
When To Use
When to use: This equation is used when a reversible chemical reaction has reached dynamic equilibrium in a closed system at constant temperature. It applies to solutes in a solution or gases, provided their concentrations are expressed in molarity (mol/L).
Why it matters: The value of Kc indicates the extent of a reaction; a large Kc favors products, while a small Kc favors reactants. This is essential for industrial chemists to calculate theoretical yields and optimize reaction conditions for maximum efficiency.
Avoid these traps
Common Mistakes
- Including solids or pure liquids.
- Forgetting to use equilibrium concentrations.
One free problem
Practice Problem
In the reversible reaction N₂O₄(g) ⇌ 2NO₂(g), a chemist measures the equilibrium molarities and determines that the expression [NO₂]² / [N₂O₄] yields a value of 0.00463. Calculate the equilibrium constant Kc for this reaction.
Solve for:
Hint: At equilibrium, the equilibrium constant Kc is numerically equal to the concentration ratio of products to reactants.
The full worked solution stays in the interactive walkthrough.
References
Sources
- Atkins' Physical Chemistry
- IUPAC Gold Book: Equilibrium constant, Kc
- Wikipedia: Equilibrium constant
- IUPAC Gold Book
- NIST Chemistry WebBook
- Atkins' Physical Chemistry, 11th Edition
- IUPAC Gold Book (Compendium of Chemical Terminology)
- Chemistry by Raymond Chang, 12th Edition