Ammonium carbonate has which solubility in water?

• A. Soluble
• B. Insoluble
• C. Reacts with water
• D. Decomposes slowly

Answer: (A)

Solubility in water is determined by whether the ions can become hydrated enough to overcome the solid’s lattice energy. A broad rule is that ammonium salts dissolve well in water, so they are soluble. Ammonium carbonate is made of ammonium ions (NH4+) and carbonate ions (CO3^2-). When it is added to water, it dissociates into those ions, which are surrounded and stabilized by water molecules. The energy released from this hydration is enough to overcome the lattice energy of the solid, so the compound dissolves to form an aqueous solution.

This isn’t a chemical reaction with water at room temperature, and the substance doesn’t decompose slowly in water under normal conditions. Decomposition of ammonium carbonate mainly occurs on heating, producing ammonia and carbon dioxide.