Ammonium iodide dissociates reversibly to ammonia and hydrogen iodide.

Question

NH4I(s) <==> NH3(g) + HI(g)

At 400°C, Kp = 0.215. Calculate the partial pressure of ammonia at equilibrium when a sufficient quantity of ammonium iodide is heated to 400°C.

Please help! would it just be the same Kp since it says its being heated to the same degree?

Answer 1

The problem gives you the Kp at 400 C. We presume the reaction is at the same temperature as Kp is given
Kp = pNH3*pHI
NH4I(s) ==> NH3(g) + HI(g)
..............p.......p
Substitute p into Kp expression and solve for p.