Question

Please help with these questions:

At 40 degrees Celsius, N2O4 (g) is 38% dissociated into NO2 at a pressure of 1 atm:
a) Calculate Kp
b) Calculate the percentage dissociation at the same temperature but at a pressure of 3 atm

Answer 1

N2O4 --> 2NO2.

The Kp for this reaciton is Kp = [NO2]^2/[N2O4]
** Note that the square brackets are really implying Partial pressures.

Answer 2

I find it best to use the "I.C.E." table technique. it stands for Inital, Change and Equilibrium.

N2O4 --> 2 NO2
Inital 1 Atm 0
Change -.38 atm +2(.38) (the .38 is for 38% decomposition)
End .62 atm .76 atm

Plugging it into the Kp we get

Kp = (.76^2)/.62


for part b repeat the process starting with 3 atm as the initial pressure for dinitrogentetroxide