Question

ALEKS Ammonia will decompose into nitrogen and hydrogen at high temperature. An industrial chemist studying this reaction fills a 5.0L flask with 2.7 atm of ammonia gas, and when the mixture has come to equilibrium measures the amount of nitrogen gas to be 0.54 atm.
Required:
Calculate the pressure equilibrium constant for the decomposition of ammonia at the final temperature of the mixture.

Answer 1

2NH3(g) = N2(g) + 3H2(g)

Before decomposed :

P NH3 = 2.7 atm

After decomposed :

P N2 = 0.54 atm

P H2 = P N2 / 3 = 0.54 / 3 = 0.18 atm

P NH3 = 2.7 - 2(0.18) = 2.34 atm

Pressure equilibrium constant :

Kp = (P N2)(P H2)³ / (P NH3)²

Kp = (0.54)(0.18)³ / (2.34)²

Kp = 5.75 × 10^(-4)