(NH4)2CO3 <-> 2NH3 + CO2 + H2O

Question

solid (NH4)2CO3 is placed in an evacuated container at 115C. When equilibrium is reached Kp = 1.93x10^-3. Extra NH3 gas is added, when equilibrium is reestablished, the partial pressure of NH3 is four times the partial pressure of H20. What is the partial pressure of NH3?

Answer 1

I believe this problem is solved this way.
........(NH4)2CO3 ==> 2NH3 + CO2 + H2O
If H2O is p, then CO2 is p and NH3 is 4p.

Substitute into Kp expression and solve for p and 4p.