Ammonium chloride, also known as Sal ammoniac, is a compound of ammonia (NH3) and chlorine (Cl). It is denoted by the symbol NH4Cl and is in solid crystalline form in nature. This compound is a water-soluble salt of ammonia, and aqueous ammonium chloride is slightly acidic. Ammonium chloride is produced commercially by reacting ammonia (NH3) with hydrochloric acid (HCl): NH3 +HCl = NH4Cl.
TL;DR (Too Long; Didn't Read)
Ammonium chloride, a water-soluble salt of ammonia, is slightly acidic as a water-based solution. The acidic component of ammonium chloride (Cl-) produces hydrogen (H+) ions when dissolved in water. The basic component (NH4+) produces hydroxide (OH-) ions when dissolved in water.
Aqueous Ammonium Chloride
When you dissolve ammonium chloride crystals in water (H2O), the ammonium chloride compound decomposes into its component ions: NH4+ and Cl-. The dissociation chemical reaction is: NH4Cl(solid) = NH4+(aqueous) + Cl-(aqueous). NH4+(aqueous) +H2O(liquid) = NH3(aqueous) +H3O+(aqueous) H3O+ +OH- = 2H2O. This particular reaction of water molecules is reversible as such H2O molecules dissociate to form H3O+ and OH- and associate to form H2O molecules. The ammonium chloride goes back to its solid form by crystallization.
The acidic or the basic components of ammonium chloride can be determined only at its aqueous form by dissolving the compound with water. The acidic component produces hydrogen (H+) ions when dissolved in water. Cl- is the acidic component of ammonium chloride. NH4Cl + H2O = NH4+ + HCl (equation 1). Cl- + H2O = H+ Cl- +H2O (equation 2). The chloride (Cl-) first associates with water ( H2O) to form hydrochloric acid (HCl) and the dissociation of HCl produces hydrogen ions (H+).
A basic component produces hydroxide (OH-) ions when dissolved in water. In aqueous solution of ammonium chloride, ammonium ions (NH4+) first associate with H2O and form ammonia and hydroxide ions. NH4+ + H2O = NH3 + OH- (equation 3). Since ammonium ions produce hydroxide ions, NH4+ are the basic components.
Acidic Nature and Uses
The slightly acidic nature of ammonium chloride is due to the formation of hydrochloric acid (HCl), because HCl is a strong acid and its effect is dominant. Determine the acidic or basic nature by using a pH meter. Ammonium chloride is used as a fertilizer for growing crops like corn, wheat, barely and rice due to its higher ammonia content. It is also used in snow treatment on ski slopes at temperatures above zero degrees Celsius/32 degrees Fahrenheit to harden snow.