Reaction of a strong acid with a weak base: HI and
In equation (10) where the weak base is reformed, the reaction is an example of a hydrolysis reaction. The ammonium ion prefers to react with the hydroxide ion rather than with the iodide ion. Since HI is a strong acid, its conjugate base is a weak base. Therefore, the hydroxide ion is more reactive. Thus the weak base is reformed, but the hydroxide concentration is lower. The pH of the solution is therefore slightly acidic.