Enter your Kc Value, Temperature, and Δn (Change in moles of gas) into the Kp Calculator to find the equilibrium constant Kp — or flip it around and solve for Kc by selecting what you want from the I want to dropdown, with the RT Factor and Formula Used shown alongside your result.
Calculated Value
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RT Factor
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Formula Used
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Kp is the equilibrium constant expressed in terms of partial pressures of gases, while Kc uses molar concentrations. Kp only considers gaseous species, whereas Kc includes all species in solution. Both constants describe the same equilibrium but use different units and expressions.
Use the formula Kp = Kc(RT)^Δn, where R is the gas constant (0.08314 L·atm/mol·K), T is temperature in Kelvin, and Δn is the difference between moles of gaseous products and reactants. This conversion accounts for the difference between concentration and pressure units.
Δn represents the change in the number of moles of gas during the reaction. Calculate it as (moles of gaseous products) - (moles of gaseous reactants). Only count gases in this calculation; solids and liquids are excluded.
Kp equals Kc when Δn = 0, meaning there's no change in the number of moles of gas during the reaction. In this case, the RT factor becomes 1, and both equilibrium constants have the same numerical value regardless of temperature.
Yes, you can use various pressure units like atm, kPa, bar, Torr, or mmHg. However, the gas constant R value must match your chosen pressure unit. For atm, use R = 0.08314 L·atm/mol·K.
Temperature affects the relationship between pressure and concentration through the ideal gas law. The RT term in the conversion formula accounts for this relationship, making temperature essential for accurate conversions between Kp and Kc.
When Δn is negative, there are fewer moles of gaseous products than reactants. This makes (RT)^Δn less than 1, so Kp will be smaller than Kc. The conversion formula still applies normally with the negative exponent.