4.4.22+23 Production of Ammonia and Proof of Ammonium Chloride

1.		2.
	Experimental Setup		Ammonium chloride gas

Photo 1:

Ammonia Production: Sodium hydroxide pellets are placed in a 250 ml double-necked flask. A saturated ammonium chloride solution is carefully dripped from a dropping funnel that has been pressure equalized. Ammonia is formed according to:

NH₄Cl + NaOH > NH₃ + NaCl + H₂O

Photo 2:

Proof of Ammonium Chloride: The ammonia gas that forms is guided into a glass beaker filled with hydrochloric acid. A white ammonium chloride fog (salmiac) is created according to:

NH₃ + HCl > NH₄Cl

This experimental setup presents a common procedure for producing ammonia in the lab. However, for industrial purposes ammonia is manufactured from raw elements according to the Haber-Bosch Procedure:

3 H₂ + N₂ > 2 NH₃

During this exothermic (reaction enthalpy: - 92.28 kJ/mol) reaction, the volume decreases, and with decreasing temperature and increasing pressure the balance shifts to the right side, i.e. the optimal NH₃ replacement is theoretically realized by a low temperature and high pressure. However, at room temperature the speed of replacement is unmeasurably small. Catalyzers currently in use first have an effect when temperatures exceed 400°C. However, at this temperature and atmospheric pressure the ammonia yield lies in the region of only 1 percent, which is not economically acceptable. For this reason, one generally works with a higher pressure, in the neighborhood of 150-250^. 10⁵ Pa. In this manner, a yield in the neighborhood of 15 percent is achieved.

Exercise 4.4.22.1:
Solution:

Using Hess’ Theorem, calculate the energy of formation for ammonium chloride

using the following reaction enthalpies:

Exercise 4.4.22.2:
Solution:

In a stoichiometric mixture of N₂ and H₂ at equilibrium at 200 bar and 470 °C, 20 percent of the volume is ammonia. Calculate the equilibrium constant for these conditions.

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