Sulfur Dioxide Characteristics and Preparing | SO₂

Sulfur dioxide is an acidic, toxic and has an rotten smell characteristics. It can be prepared by burning sulfur or metal sulfide compound or hydrogen sulfide with oxygen. Sulfuric acid can be reduced to sulfur dioxide because sulfuric acid is an oxidizing acid. It is used in many industrial applications.

Characteristics of SO₂

Here, we are going to learn about few characteristics of sulfur oxide and their effects.

Acidity

SO₂ is an acidic gas which dissolve in water to produce sulfurous acid (H₂SO₃). It is a weak acid.

If, SO₂ is oxidized to SO₃ by O₂ and dissolve in water, sulfuric acid (H₂SO₄) is given.

This causes to acid rain which is one of the major environmental pollution method.

Colourless, pungent odor

We cannot see a colour in SO₂ gas. Therefore we cannot identify it by colour. Human nose can identify this pungent odor. SO₂ is heavier than air.

Toxicity

0 - 0.1 ppm range is not dangerous. But more than that, it causes many health problems. Over 5 ppm, warnings of emergency situations should be activated.

Sulfur dioxide effects on health

Preparation of sulfur dioxide

Sulfur, metal sulfide, metal sulfite compounds, sulfuric acid can be used to prepare SO₂ gas with other different compounds at different physical conditions.

Burning S, metal sulfide, hydrogen sulfide

This method is used to prepare SO₂ in industry to manufacture sulfuric acid. Sulfur (s), hydrogen sulfide (H₂S) or metal sulfide (Na₂S) can be used to produce SO₂.

Hot concentrated sulfuric acid and Copper | H₂SO₄ + Cu

Add concentrated sulfuric acid to copper and heat the solution. Then SO₂, copper sulfate (CuSO₄) and water are given. CuSO₄ is blue colour.

Dilute acids and metal sulfite

Solid metal sulfite compounds react with dilute acids and give SO₂.

Dilute acid and thiosulfate reaction | S₂O₃^2- + H⁺

Add a dilute acid to metal thiosulfate ( S₂O₃^2-). It gives SO₂ and sulfur which is deposited as a pale yellow solid. This reaction is used to identify thiosulfate ion from sulfate ion in qualitative analysis.

Sulfur and hot concentrated sulfuric acid | S + H₂SO₄

Sulfur is heated with concentrated sulfuric acid. S is oxidized to S and sulfuric is reduced to S too.

Carbon and hot concentrated sulfuric acid | C + H₂SO₄

Carbon is oxidized to carbon dioxide (CO₂) and sulfuric acid is reduced to SO₂.

Sulfur dioxide producing industries

Petroleum Industry

- Crude oil contains sulfur as different compounds. These sulfur is removed or reduced in refining process. But some fuels contains little bit sulfur amount. When fuel oil is burnt in furnaces to generate the heat, SO₂ is released. Sulfur in the crude oil is converted to H₂S in sulfur removing process. If H₂S is not used to produce another product such as sulfuric acid, H₂S is burnt. It also produces SO₂.

Sulfuric Acid Manufacturing - Contact process

S or metal sulfide is burnt to produce SO₂.

Cement Industry