Question

NH₄ CN (a solid) is warmed in a chamber and the following reaction occurs: NH₄CN(s) -> HCN(g) + NH₃ (g)

When the reaction chamber initially containing only NH₄ CN is warmed the pressure of HCN was found to be .06 atm.

a. Write down the equilibrium expression Kp for this reaction.

b. Based on the information provided determine the value of Kp.

This is how the entire question reads? Exactly what other information are you requesting?

Answer 1

Ans. Balanced reaction-       NH₄CN(s) ------> HCN(g) + NH₃(g)

# Following stoichiometry of balanced reaction, 1 mol NH₄CN forms 1 mol each of HCN and NH₃.

# Following Avogadro’s Law, equal volume of all gases have equal number of moles, at constant pressure and temperature.

So, the moles of NH₃, and in turn, the volume (and subsequently its pressure) must be equal to that of HCN formed.

# So-

            Amount of HCN formed = 0.06 atm

            Amount of NH₃ formed = 0.06 atm

#A. Equilibrium expression

Equilibrium constant, Kp = pHCN x pNH₃

Note that the solids are excluded from Kp expression.

#B. Putting the values in above expression-

            Kp = 0.06 x 0.06 = 0.0036