Question

Explain the reaction between dil. HCl and Sodium sulphite.

Answer 1

Sodium sulphite is a metal derivative of trioxide of sulphur element. Oxides of sulphur are unstable in nature and undergo chemical reactions with metal to form their stable derivatives.
Physical properties of Sodium sulphite are it is off-white to white in colour and have no distinct odour.

Complete answer:
Reaction between dil. HCl and Sodium sulphite is one of the laboratory methods of preparation of sulphur dioxide.
When Sodium sulphite undergoes reaction with dil. HCl in the laboratory will result in the formation of sodium chloride salt, water and release of sulphur dioxide gas.
$N{a_2}S{O_3} + 2HCl \to 2NaCl + {H_2}O + S{O_2} \uparrow$
Where $N{a_2}S{O_3}$ is sodium sulphite
$HCl$ is hydrochloric acid
$NaCl$ is sodium chloride
${H_2}O$ is water
$S{O_2}$ is sulphur dioxide
The sulphur gas released as the product of reaction has a significant metal burning like odour. Which means that formation of the product is easily observed by the characteristic smell of sulphur dioxide gas.
Reaction between dil. HCl and Sodium sulphite causes displacement of sulphur trioxide from its compound to form sulphur dioxide.
In a similar way hydrogen is replaced from hydrochloric acid to form water.
In the reaction both the reactants undergo displacement to produce newer products.
Since, the above reaction is preceded by displacement of atoms from their compound to form a new compound this reaction is known as double displacement reaction.
Hence, we see the reaction between dil. HCl and Sodium sulphite is a type of double displacement reaction which will lead to formation of sodium chloride, water and sulphur dioxide gas.

Note:
Sulphur dioxide gas is highly soluble in water and forms a strong acid known as sulphuric acid.
Atmospheric sulphur dioxide gas combines with water vapours and becomes one of the reasons for acid rain.