Chapter 22, Problem 39R

To determine

To Explain: The reason for ammonia being basic, even though it contains no hydroxide ions.

To Infer:If it is a strong or weak base.

Explanation of Solution

Introduction:Bases are compounds that gives ${\text{OH}}^{-}$ ions in water or accepts ${\text{H}}^{+}$ ions from acids.

Although ammonia does not contain any ${\text{OH}}^{-}$ ions in its chemical formula, it accepts ${\text{H}}^{+}$ ions from water, which makes it a base. In an aqueous solution, ammonia attracts a ${\text{H}}^{+}$ ion from a water molecule thereby forming a ${\text{NH}}_4^{+}$ ion and a ${\text{OH}}^{-}$ ion.

The chemical equation for the reaction:

  ${\text{NH}}_3{\text{+H}}_2\text{O}\to {\text{NH}}_4^{+}+{\text{OH}}^{-}$

Ammonia dissociates only partially in water forming a few ${\text{OH}}^{-}$ ions and most of it remains in the form of ${\text{NH}}_4^{+}$ . Thus, ammonia is a weak base.

Conclusion:Ammonia is a weak base as it accepts ${\text{H}}^{+}$ ions from water and forms only few ${\text{OH}}^{-}$ ions in it.