Kc is the equilibrium constant with respect to concentration and Kp is the equilibrium constant with respect to pressures. When the moles of gas on both sides of the equation are the same, these two values are equal. When there are different numbers of moles of gas on either side, as in this reaction, then we have to use the following relationship

Kp = Kc(RT)^deltan

Where R is the ideal gas constant, T is the temperature in Kelvin (assuming T = 25 degC since no temperature is given), and deltan is the change in number of moles (products - reactants).

Since we know Kp and are trying to find Kc, we can rearrange the equation to

Kc = Kp/((RT)^deltan)

Kc = (1.5x 10^-5)/((0.08206*298)^(2-4))

Kc = (1.5x10^-5) / 0.00167

Kc = 8.97 x 10^-3

## See eNotes Ad-Free

Start your **48-hour free trial** to get access to more than 30,000 additional guides and more than 350,000 Homework Help questions answered by our experts.

Already a member? Log in here.