Kp to Kc Conversion Calculator (Equilibrium Constants of Gas Reactions)
Converts the equilibrium constant of a gas reaction between concentration form Kc and pressure form Kp for a given temperature and change in moles of gas.
Results
Kp from Kc, pressures in atm
0.014200
Kp from Kc, pressures in bar
0.013831
Kc from the Kp you entered (atm)
42.2545
Conversion factor (RT)^Δn
0.000284
The dashed line marks the value you entered.
What this tool does
The two constants are the same equilibrium written in different units, linked by Kp = Kc (RT)^Δn, where Δn is moles of gaseous products minus moles of gaseous reactants. When Δn is zero, as in H₂ + I₂ ⇌ 2 HI, they are equal; otherwise the number depends on the pressure unit, so always say whether Kp is in atm or bar. Temperature must be absolute, and only gases count in Δn: solids and liquids drop out of both constants.
Formula
Kp = Kc (RT)^Δn · Kc = Kp ÷ (RT)^Δn (R = 0.082057 L·atm/(mol·K) for atm, 0.083145 L·bar/(mol·K) for bar)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
kc | Kc (concentrations in mol/L) | — |
kp | Kp (pressures in atm) | — |
tc | Temperature | °C |
dn | Change in moles of gas, Δn (products − reactants) | — |
KP | Kp from Kc, pressures in atm | — |
KB | Kp from Kc, pressures in bar | — |
KC | Kc from the Kp you entered (atm) | — |
F | Conversion factor (RT)^Δn | — |
Worked example
- Kc (concentrations in mol/L)50
- Kp (pressures in atm)0.012
- Temperature450 °C
- Change in moles of gas, Δn (products − reactants)-2
- Kp from Kc, pressures in atm0.014200
- Kp from Kc, pressures in bar0.013831
- Kc from the Kp you entered (atm)42.2545
- Conversion factor (RT)^Δn0.000284
Limitations
- Mixing units is the most common source of error. Convert every input to the units shown next to each field before calculating.
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.