Question

When alum is added to water what is chemical formula of the precipitate

Answer 1

Crystal of potassium alum

Aluminium-based alums are named by the monovalent cation. Unlike the other alkali metals, lithium does not form alums; a fact attributed to the small size of its ion.

The most important alums are

Potassium alum, KAl(SO

4)

2·12H

2O, also called "potash alum" or simply "alum".

Sodium alum, NaAl(SO

4)

2·12H

2O, also called "soda alum" or "SAS".

Ammonium alum, NH

4Al(SO

4)

2·12H

2O.

which alum