Question

Heating an aqueous solution of aluminum chloride to dryness?
(A) $ AlC{l_3} $
(B) $ A{l_2}C{l_3} $
(C) $ A{l_2}{O_3} $
(D) $ Al\left( {OH} \right)C{l_2} $

Answer 1

Hint: Aluminum chloride is an inorganic salt that reacts with water to form an acidic solution. As aluminum chloride upon treatment with water forms aluminum tri hydroxide and hydrochloric acid. This aluminum tri hydroxide upon dryness loses water molecules to form aluminum oxide.

Complete answer:
Salt is the combination of two ions mainly cation and anion. Aluminum can act as a cation and chlorine acts as an anion and forms an inorganic salt known as aluminum chloride. Aluminum chloride has the molecular formula of $ AlC{l_3} $ . It reacts with water to form an acidic solution. The chemical reaction will be as follows:
 $ AlC{l_3} + 3{H_2}O \to Al{\left( {OH} \right)_3} + 3HCl $
As hydrochloric acid is formed in the reaction, the solution is acidic.
 Given that an aqueous solution upon dryness means the above solution formed under dryness means there is a dehydration process. The loss of water molecules takes place from the aluminium tri hydroxide. The chemical reaction will be as follows:
 $ 2Al{\left( {OH} \right)_3}\xrightarrow{\Delta }A{l_2}{O_3} + 3{H_2}O $
The products formed in the above reaction is aluminium oxide. It has the molecular formula of $ A{l_2}{O_3} $ .
Thus, heating an aqueous solution of aluminum chloride to dryness will give aluminum oxide with molecular formula $ A{l_2}{O_3} $
Option C is the correct one.

Note:
Heating an aqueous solution of inorganic salts forms an acidic solution mainly as chlorine from salt and hydrogen from water forms an acidic solution. But upon dehydration loses water molecules but not form a previous salt but forms an oxide which is amphoteric. Thus, chemical reactions must have to write for these reactions.