Question

1. Which feature of ammonia molecule leads to the formation of the ammonium ion when ammonia dissolves in water?
2. Name the other ion formed when ammonia dissolves in water.
3. Give one test that can be used to detect the presence of the ion produced in (b).

Answer 1

1. Ammonia molecule has a lone pair of electrons on it's nitrogen atom. \[\begin{array}{cc}
   \phantom{...........}\ce{H}\\
   \phantom{...........}|\\
   \ce{Lone pair -> ^{\bullet}_{\bullet}\mathbf{N} - H}\\
   \phantom{...........}|\\
   \phantom{...........}\ce{H}\\
   \end{array}\]
   Due to this lone pair of electrons, in aqueous solutions it forms ammonium ion.
   \[\ce{NH3 + H2O -> NH4OH}\]
   \[\ce{NH4 + <=> NH_4+ + OH}\]
2. Hydroxyl ion \[\ce{OH-}\].
3. The red litmus paper turns blue in the solution.