Convert Kc to Kp

The Conversion of K_c to K_p calculator uses the formula K_p = K_c * RT^(n-n0) to compute an equilibrium constant in terms of pressure by using an equilibrium constant in terms of molarity. 

INSTRUCTIONS: Choose units and enter the following:

• (K_c) Equilibrium constant in terms of molarity (mols/L)
• (T) Temperature 
• (n) Number of moles of products in the gas phase
• (n₀) Number of moles of reactants in the gas phase

Equilibrium Constant (K_p):  The calculator returns the equilibrium constant (K_p) in kilo-pascals.  However, this can be automatically converted to other pressure units via the pull-down menu.

Related Items:

• Relationship between temperature and volume, Charles Law Calculator:
  • `V_1`•`T_2` = `V_2`•`T_1`
• Relationship between pressure and volume: Boyles Law Calculator
  • `P_1`• `V_1` = `P_2` •`V_2`
• Relationship between temperature and pressure, Gay-Lussac Law:
  • `T_1`•`P_2`=`T_2`•`P_1`
• Relationship between temperature, volume and pressure, Combined Gas Law Calculator:
  • P•V / T = k
• Relationship between pressure, volume, moles and temperature, Ideal Gas Law:
  • P•V = n•R•T

The Science

Note: in this formula, only gaseous substances are taken in to consideration. Aqueous species are taken into account when calculating other equilibrium constants, but this equation focuses specifically on gaseous species with partial pressures.

Equilibrium constants can be used to predict the direction that a reaction will proceed, and is useful in chemistry, biology, and biochemistry. When K > 1, equilibrium favors the products, and when K < 1, equilibrium favors the reactants.

The Math

The formula to compute the equilibrium constant in terms of pressure (pascals) is as follows:

            K_p = K_c * RT^(n-n0)

where: 

• Kp is the equilibrium constant in terms of pressure with pascals.
• K_c = equilibrium constant in terms of molarity (mols/L)
• R = ideal gas constant (0.08206 L*atm/mols*K)
• T = temperature (Kelvin)
• n = number of moles of products in the gas phase
• n₀ = number of moles of reactants in the gas phase

References

Whitten, et al. "Chemistry" 10th Edition. Pp. 734

ChemWiki

See Also

Acid Equilibrium Constant (Ka)

Base Equilibrium Constant (Kb)