Kp (Equilibrium Constant, Pressure) Calculator

Calculate the equilibrium constant (Kp) for gas-phase reactions using partial pressures.

Enter the details of your chemical reaction, including reactants, products, their stoichiometric coefficients, and partial pressures. Optionally, convert between Kp and Kc using temperature and gas constant.

Examples

See how to use the Kp Calculator with real chemical reactions.

Kp Calculation for Ammonia Synthesis

Calculate Kp

Calculate Kp for the reaction: N2(g) + 3H2(g) ⇌ 2NH3(g) at 400K.

Calculation Type: kp

Reactants: N2 (coef: 1, P: 0.8 atm), H2 (coef: 3, P: 0.6 atm)
Products: NH3 (coef: 2, P: 0.2 atm)

Temperature (K): 400 K

Gas Constant (R): 0.0821

Kp Calculation for Decomposition of CaCO3

Calculate Kp

Calculate Kp for: CaCO3(s) ⇌ CaO(s) + CO2(g) at 298K.

Calculation Type: kp

Reactants: CaCO3 (coef: 1, P: 0 atm)
Products: CO2 (coef: 1, P: 0.25 atm)

Temperature (K): 298 K

Gas Constant (R): 0.0821

Convert Kc to Kp for SO2 Oxidation

Convert Kc to Kp

Given Kc = 4.0 at 500K for: 2SO2(g) + O2(g) ⇌ 2SO3(g), find Kp.

Calculation Type: kcToKp

Temperature (K): 500 K

Gas Constant (R): 0.0821

Kc Value: 4.0

Δn (mol difference): -1 mol

Convert Kp to Kc for Hydrogen Iodide Formation

Convert Kp to Kc

Given Kp = 0.5 at 700K for: H2(g) + I2(g) ⇌ 2HI(g), find Kc.

Calculation Type: kpToKc

Temperature (K): 700 K

Gas Constant (R): 0.0821

Kp Value: 0.5

Δn (mol difference): 0 mol

Other Titles
Understanding Kp (Equilibrium Constant, Pressure) Calculator: A Comprehensive Guide
Master the calculation of equilibrium constants for gas-phase reactions using partial pressures.

What is Kp?

  • Definition of Kp
  • Relation to Chemical Equilibrium
  • Difference Between Kp and Kc
Kp is the equilibrium constant for gas-phase reactions, expressed in terms of partial pressures. It provides insight into the position of equilibrium and the extent of a reaction.
Kp vs. Kc

Kp in Real Reactions

  • For the reaction: N2(g) + 3H2(g) ⇌ 2NH3(g), Kp is calculated using the partial pressures of NH3, N2, and H2.
  • Kc uses concentrations, while Kp uses partial pressures.

Step-by-Step Guide to Using the Kp Calculator

  • Inputting Reaction Data
  • Choosing Calculation Type
  • Interpreting Results
Start by entering the reactants and products, their coefficients, and partial pressures. Select the calculation type: direct Kp calculation or conversion between Kp and Kc. Enter temperature and gas constant if needed.
Step-by-Step Example

Sample Calculation

  • Input: N2 (1, 0.8 atm), H2 (3, 0.6 atm), NH3 (2, 0.2 atm), T = 400K.
  • Result: Kp = 0.013.

Real-World Applications of Kp

  • Industrial Chemical Processes
  • Laboratory Experiments
  • Academic Research
Kp calculations are essential in designing chemical reactors, optimizing industrial processes, and analyzing laboratory experiments involving gases.
Why Kp Matters

Industrial Examples

  • Ammonia synthesis in the Haber process relies on Kp calculations.
  • Kp helps determine optimal conditions for maximum yield.

Common Misconceptions and Correct Methods

  • Ignoring Units
  • Incorrect Δn Calculation
  • Mixing Kp and Kc Formulas
Always use consistent units for pressure and temperature. Calculate Δn as the difference in moles of gaseous products and reactants. Use the correct formula for the chosen calculation type.
Avoiding Mistakes

Tips for Accuracy

  • Δn is only for gases; solids and liquids are not included.
  • Use Kelvin for temperature, not Celsius.

Mathematical Derivation and Examples

  • Kp Formula Derivation
  • Kp-Kc Relationship
  • Worked Examples
Kp is derived from the law of mass action, relating partial pressures to equilibrium concentrations. The relationship between Kp and Kc involves the gas constant and temperature.
Formulas and Calculations

Key Formulas

  • Kp = Kc(RT)^Δn
  • Kc = Kp/(RT)^Δn