Question

(15 points) Ammonium iodide dissociates reversibly to ammonia and hydrogen iodide. NH4I (s) ⇌ NH3 (g) + HI (g) At 400 ºC, Km = 0.215. Calculate the partial pressure of ammonia at equilibrium when a sufficient quantity of ammonium iodide is heated to 400 ºC. Complete the ICE box below as part of your answer
A. 0.103 atmB. 0.215 atmC. 0.232 atmD. 0.464 atmE. 2.00 atm

Answer 1

Answer:

D. 0.464 atm

Explanation:

Lets set up the ice box realizing  that at at equilibrium the pressure of ammonia will equal the HI pressure given that they are produced in a 1:1 ratio. Also we should remember that the expression for equilibrium does not include pure solids.

The equilibrium is

           NH4I (s)           ⇌             NH3 (g) + HI (g)  Km= 0.215 @ 400 ºC

I   sufficient quantity                      0              0

C             -z                                    +z            +z

E   sufficient quantity - z                z              z

Km = pNH3 x pHI = 0.215 =  z² = 0.215  ∴ z = √0.215 = 0.464 atm