Ammonium iodide, a solid, decomposes to give NH3(g) and HI(g). At 408 °C, some N
ID: 1089684 • Letter: A
Question
Ammonium iodide, a solid, decomposes to give NH3(g) and HI(g). At 408 °C, some NH4I(s) is placed in an evacuated container. A portion of it decomposes, and the total pressure at equilibrium is 1.12 atm. Extra NH3(g) is then injected into the container, and when equilibrium is reestablished, the partial pressure of NH3(g) is 1.30 atm. (a) Compute the equilibrium constant in terms of pressures, Kp, for the decomposition of ammonium iodide at 408 °C. NH41(s) 13(g) + HI(g) K= (b) Determine the final partial pressure of HI(g) in the container. PHI = atmExplanation / Answer
NH4I(s) <-----> NH3(g) + HI(g)
pTOtal = pNH3+ pHI
1.12 = x+x
x = 0.56 atm
Kp = pNH3*pHI
= 0.56*0.56
= 0.3136
b)
NH4I(s) <-----> NH3(g) + HI(g)
at equili 0.56 0.56
add +x -
re-established 1.3 0.56-x
Kp = pNH3*pHI
0.3136 = (0.56-x)*1.3
pHI at equilibrium = 0.56-0.32 = 0.24 atm