Question

On reaction with sulphuric acid solution, barium chloride forms a white precipitate of ………. sulphate.

Answer 1

Hint :Barium chloride is salt. When an acid reacts with a salt, it displaces the anion and forms a new compound. Identify the Lewis acid and Lewis base combinations while also looking at the charge on each entity in the compounds mentioned.

Complete Step By Step Answer:
Barium chloride is a salt made of the positive charge Barium cation and negative charge chloride anion. In the same way, sulphuric acid is made of a proton (hydrogen) and anion ($SO_{4}^(2-)$). Sulphuric acid is a strong acid and it easily dissociates into cation and anion.
Once it is in contact with barium chloride, a chemical reaction occurs.
Barium is a cation with a 2+ charge and sulphate is an anion with 2- charge. Therefore, sulphate donates two electrons with barium and forms barium sulphate.
Also, hydrogen from sulphuric acid behaves as a Lewis acid. And chloride ions behave as a Lewis base.
Lewis acids are defined as chemical species that contain an empty orbital which is capable of accepting an electron from a Lewis base.
Similarly, Lewis bases are chemical species that can donate an electron pain to a Lewis acid.
Hydrogen has a 1+ charge and chloride has a 1- charge. Thus, chloride transfers an electron to hydrogen and forms the compound hydrogen chloride.
Barium sulphate is another salt precipitate of white colour.
The balanced chemical equation for the above reaction is:
$BaCl_2(s) +H_2 SO_4(aq) BaSO_4(s) +2HCl_((aq) )$.

Note :
Such questions are easier to solve as it is simple displacement reactions by an acid – here, sulphuric acid. Remember that sulphuric acid is a strong acid and can displace metals from their compounds. You will need to remember this mechanism for other salts as well.