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Gas Equilibrium Constants and Pressure Quotients

Convert numerical Kc to Kp on a chosen pressure convention or form a four-species pressure quotient.

Formula & worked example
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How to use this calculator

Enter the known values in the units shown. Results update as you type.
Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
Use the worked example to check the method. Reset restores the starting fields.

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Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

For Delta n = 0, numerical Kp equals numerical Kc.

Kp = Kc (RT)^Delta n; pressure quotient = PC^c PD^d /(PA^a PB^b)

Worked example

Enter these known values and leave the other values blank.

I want to:: convert between Kₚ and K꜀
Equilibrium constant (K꜀): 2
Temperature (T): 300 K
Number of moles of products (n): 1 mol
Number of moles of reactants (n₀): 1 mol

Equilibrium constant (Kₚ): 2

Assumptions and limitations

Conversion mode assumes ideal gases and molar concentrations, with pressure scale matched to the selected R value. Captured R choices are rounded legacy constants; their printed digits are not a modern uncertainty estimate.
Pressure-quotient mode uses the internal Pascal pressure basis and exponents from a balanced gas reaction. Thermodynamic equilibrium constants instead use dimensionless activities relative to specified standard states.
Bookify corrects the captured fourth-product term to PD raised to coefficient d, rather than PD multiplied by d. Singular logarithmic coefficient inverses cannot determine a coefficient from a unit numerical pressure.

Common questions

What does this model assume?

Conversion mode assumes ideal gases and molar concentrations, with pressure scale matched to the selected R value. Captured R choices are rounded legacy constants; their printed digits are not a modern uncertainty estimate.

Can I solve backward?

Clear the unknown value and enter compatible known values. Choices, one-way outputs and singular boundary cases cannot always be inverted.

References

A balanced pressure quotient raises every partial pressure to its stoichiometric coefficient. Replace the fourth-product multiplication with exponentiation and independently rearrange all supported roots/logarithmic inverses. The Kp/Kc conversion identity is unchanged.

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