Question

Explain with equations how sulphur dioxide(SO₂) is prepared in the laboratory.

Answer 1

It is found in exhaust emissions of an internal combustion engine,

• In the industrial areas where coal and petroleum are used as fuels.
• In nature, it is found in volcanic gases.

Sulphur(S) react with Oxygen(O₂) above 300^oC two types of oxides are formed.

i) $$\begin{gathered} \mathrm{S}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\stackrel{{800}^{\mathrm{o}}\mathrm{C}}{\to }{\mathrm{SO}}_2\left(\mathrm{g}\right) \\ \mathrm{Sulphur}\mathrm{Oxygen}\mathrm{Sulphur}\mathrm{dioxide} \end{gathered}$$

ii)$$\begin{gathered} \mathrm{S}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\stackrel{{800}^{\mathrm{o}}\mathrm{C}}{\to }{\mathrm{SO}}_3\left(\mathrm{g}\right) \\ \mathrm{Sulphur}\mathrm{Oxygen}\mathrm{Sulphur}\mathrm{trioxide} \\ (\mathrm{trace}\mathrm{amounts}) \end{gathered}$$

Laboratory Preparation of SO₂:

Sulphur dioxide is prepared in the laboratory by heating Copper (Cu) turnings with concentrated Sulphuric acid (H₂SO₄)

$$\begin{gathered} \mathrm{Cu}\left(\mathrm{s}\right)+2{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\to {\mathrm{CuSO}}_4\left(\mathrm{aq}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+{\mathrm{SO}}_2\left(\mathrm{g}\right) \\ \mathrm{Copper}\mathrm{Sulphuric}\mathrm{acid}\mathrm{Copper}\mathrm{sulphate}\mathrm{water}\mathrm{Sulphur}\mathrm{dioxide} \end{gathered}$$

Properties of Sulphur: SO₂ gas is pungent smell.

It is sour in taste.