Question

Some NH4I is palced in a reaction placed in a closed container, which is then heated to 400 deg. C. If the total pressure in the container is (7.47x10^2) , mm Hg, what is the value of Kp. Remember to convert the pressures to atm's.

Answer 1

Answer –

We are given, total pressure = 7.47*10² mm Hg

We know reaction –

    NH₄I(s) ------> NH₃(g) + HI(g)

Pressure in atm

We know,

760 mm Hg = 1 atm

So 747 mm Hg = ?

= 983 atm

Total moles of product = 1+1 = 2 moles

So mole fraction of NH₃ = ½ = 0.50

Mole fraction of HI = ½ = 0.50

We know Dalton’s partial law

Partial pressure = mole fraction * total pressure

So partial pressure of NH₃ = 0.50 *0.983 atm

                                           = 0.491 atm

Partial pressure of HI = 0.50 *0.983 atm

                                    = 0.491 atm

Now we know, Kp = [NH₃] [HI]

                                = 0.491 atm * 0.491 atm

                                = 0.242