When a solute dissolves in water, it may simply dissociate into its constituent ions or react with the solvent. Sodium chloride, for instance, ionizes to Na⁺ and Cl⁻ without altering the water molecules. Ammonia behaves differently: as a base, it accepts a proton from water, forming new ions in the process.

Jupiterimages/Photos.com/Getty Images

Step 1: Identify the Reactants

The formula for ammonia is NH₃ and for water it is H₂O.

Step 2: Transfer a Proton

Removing a proton (H⁺) from water yields the hydroxide ion (OH⁻). Adding that proton to ammonia converts it into the ammonium ion (NH₄⁺).

Step 3: Assign Charges

The proton transfer leaves water negatively charged (OH⁻) and ammonia positively charged (NH₄⁺). Therefore, the products carry these charges.

Step 4: Write the Balanced Equation

NH₃ + H₂O → NH₄⁺ + OH⁻

Because the equilibrium constant for this base hydrolysis (K_b ≈ 1.8 × 10⁻⁵) is small, the reaction is only partially complete; ammonia remains mostly undissociated in dilute solutions.

For a deeper dive, consult the Journal of Chemical Education or the RSC Learning Chemistry page.