Question

What happens when ammonia solution is added first dropwise and then in excess to the following solution:

FeCl₃

Write a balanced equation for this reaction.

Give the reactions to explain what happens when ammonia solution is added drop by drop till it is in excess to the following solution:

FeCl₃

Answer 1

Adding ammonium hydroxide drop by drop to iron(III) chloride solution forms a reddish-brown precipitate of iron(III) hydroxide.

\[\ce{\underset{(Yellow solution)}{FeCl3} + 3NH4OH -> \underset{Ferric hydroxide}{\underset{(Reddish brown ppt.)}{Fe[OH]3\downarrow}}+ \underset{(Colourless solution)}{3NH4Cl}}\]

Adding excess ammonium hydroxide leaves the precipitate insoluble, showing no further change.