Question

Explain the reaction between dil.$\mathrm{HCl}$ and Sodium sulphite

Answer 1

Reaction of dil. $\mathrm{HCl}$ and Sodium sulphite:-

1. In the reaction of dil. Hydrochloric acid($\mathrm{HCl}$) with Sodium sulphite${\mathrm{Na}}_2{\mathrm{SO}}_3$, Sulphur dioxide gas(${\mathrm{SO}}_2$), Sodium chloride$\left(\mathrm{NaCl}\right)$ and water are formed as the products.
2. The reaction results in displacement of Sulphur trioxide from its compound to form Sulphur dioxide which gives the smell of burning sulphur.
3. Similarly from Hydrochloric acid hydrogen is replaced to form water.
4. Both the reactants undergo displacement in the reaction in order to produce new products.
5. This reaction is s double displacement reaction as the reaction is preceded by the displacement of atoms from their compound to form a new compound.
6. The complete balanced equation is : $\underset{\mathrm{Sodium}\mathrm{sulphite}}{{\mathrm{Na}}_2{\mathrm{SO}}_3\left(\mathrm{aq}\right)}+\underset{\mathrm{dil}.\mathrm{Hydrochloric}\mathrm{acid}}{2\mathrm{HCl}\left(\mathrm{aq}\right)}\to \underset{\mathrm{Sodium}\mathrm{chloride}}{2\mathrm{NaCl}\left(\mathrm{aq}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}+\underset{\mathrm{Sulphur}\mathrm{dioxide}}{{\mathrm{SO}}_2\left(\mathrm{g}\right)}$
7. This colourless gas of Sulphur dioxide (${\mathrm{SO}}_2$) having a suffocating smell of burning sulphur, changes the colour of Potassium dichromate$\left({\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7\right)$ solution from orange to green when passed through it.

Therefore, the reaction between dil.$\mathrm{HCl}$ and Sodium sulphite (${\mathrm{Na}}_2{\mathrm{SO}}_3$) produces Sulphur dioxide gas(${\mathrm{SO}}_2$), Sodium chloride$\left(\mathrm{NaCl}\right)$ and water.