Equilibrium Constant (Kc, Kp) Calculator

Calculate Kc, Kp, and Convert Between Them

Select calculation type and enter the required values. Supports both concentration (Kc) and pressure (Kp) equilibrium constants, as well as Kp ↔ Kc conversion.

Example Calculations

Click an example to load it into the calculator.

Kc for Ammonia Synthesis

Calculate Kc

Calculate Kc for the reaction: N2(g) + 3H2(g) ⇌ 2NH3(g) at 500 K. [N2]=0.2 mol/L, [H2]=0.6 mol/L, [NH3]=0.4 mol/L.

Calculation Type: Calculate Kc (Concentration)

Reactants: N2 (coef: 1, conc: 0.2), H2 (coef: 3, conc: 0.6)
Products: NH3 (coef: 2, conc: 0.4)

Temperature (K): 500 K

Kp for Decomposition of N2O4

Calculate Kp

Calculate Kp for: N2O4(g) ⇌ 2NO2(g) at 298 K. P(N2O4)=0.5 atm, P(NO2)=1.2 atm.

Calculation Type: Calculate Kp (Pressure)

Reactants: N2O4 (coef: 1, P: 0.5)
Products: NO2 (coef: 2, P: 1.2)

Temperature (K): 298 K

Convert Kp to Kc for SO2 Oxidation

Convert Kp to Kc

Given Kp=0.25 at 700 K for 2SO2(g) + O2(g) ⇌ 2SO3(g), convert to Kc. Δn = -1.

Calculation Type: Convert Kp to Kc

Temperature (K): 700 K

Gas Constant (R): 0.0821 L·atm·K⁻¹·mol⁻¹

Kp: 0.25 atm

Δn: -1

Convert Kc to Kp for Methanol Formation

Convert Kc to Kp

Given Kc=1.5 at 600 K for CO(g) + 2H2(g) ⇌ CH3OH(g), convert to Kp. Δn = -2.

Calculation Type: Convert Kc to Kp

Temperature (K): 600 K

Gas Constant (R): 0.0821 L·atm·K⁻¹·mol⁻¹

Kc: 1.5

Δn: -2

Other Titles
Understanding the Equilibrium Constant (Kc, Kp) Calculator: A Comprehensive Guide
Master chemical equilibrium calculations, Kc/Kp conversions, and real-world applications with this in-depth guide.

What is the Equilibrium Constant?

  • Definition and Purpose
  • Types of Equilibrium Constants
  • Key Concepts
The equilibrium constant (K) quantifies the ratio of product and reactant concentrations or pressures at equilibrium for a chemical reaction. It is fundamental in predicting reaction direction and extent.
Types of Equilibrium Constants
Kc is based on concentrations (mol/L), while Kp is based on partial pressures (atm). The relationship between Kc and Kp depends on temperature and the change in gas moles (Δn).
Key Concepts
Δn is the difference between the sum of gas product coefficients and gas reactant coefficients. R is the gas constant, and T is the temperature in Kelvin.

Equilibrium in Practice:

  • Calculating Kc for ammonia synthesis.
  • Converting Kp to Kc for SO2 oxidation.
  • Predicting reaction direction using K.

Step-by-Step Guide to Using the Calculator

  • Selecting Calculation Type
  • Entering Values
  • Interpreting Results
Choose whether to calculate Kc, Kp, or convert between them. Enter all required values for reactants, products, temperature, and gas constant as needed.
Input Fields and Units
For Kc, enter concentrations (mol/L); for Kp, enter partial pressures (atm). For conversions, provide temperature (K), gas constant (R), and Δn.
Understanding the Output
The result section displays the calculated equilibrium constant, the formula used, and a step-by-step breakdown of the calculation.

Calculator Usage Examples:

  • Calculate Kc for a reaction with given concentrations.
  • Convert Kp to Kc using temperature and Δn.

Real-World Applications of Equilibrium Constants

  • Industrial Chemistry
  • Environmental Science
  • Biological Systems
Equilibrium constants are essential in designing chemical reactors, controlling industrial processes, and understanding environmental and biological systems.
Industrial Applications
Engineers use Kc and Kp to optimize yields and safety in large-scale chemical production.
Environmental and Biological Relevance
K values help predict pollutant behavior and metabolic pathways in living organisms.

Applications in Science and Industry:

  • Optimizing ammonia production in the Haber process.
  • Modeling atmospheric reactions.
  • Analyzing metabolic equilibrium in cells.

Common Misconceptions and Correct Methods

  • Mixing Units
  • Ignoring Δn
  • Incorrect Temperature Use
A common mistake is to mix concentration and pressure units or to ignore Δn in conversions. Always use consistent units and provide all required values.
Avoiding Calculation Errors
Ensure all coefficients are correct, and temperature is in Kelvin. Double-check all input values and units before calculation.

Tips for Accurate Calculations:

  • Always convert °C to K by adding 273.15.
  • Check that Δn is calculated correctly.

Mathematical Derivation and Examples

  • Kc and Kp Formulas
  • Kp ↔ Kc Conversion
  • Worked Examples
Kc = ([C]^c [D]^d)/([A]^a [B]^b) for concentrations; Kp = (PC^c PD^d)/(PA^a PB^b) for pressures. Kp = Kc(RT)^Δn, where Δn is the change in gas moles.
Worked Example
Given Kp=0.25 at 700 K and Δn=-1, Kc = Kp/(RT)^Δn. Substitute values to find Kc.

Mathematical Insights:

  • Calculate Kc from Kp for a gas-phase reaction.
  • Use the calculator to check your manual calculations.