# Producing Sulfuric Acid

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## Producing sulfuric acid: The Contact process

Sulfuric acid ($$\text{H}_{2}\text{SO}_{4}$$) is produced from sulfur, oxygen and water through the Contact process. In the first step, sulfur is burned to produce sulfur dioxide ($$\text{SO}_{2}$$):

$$\text{S}(\text{s}) + \text{O}_{2}(\text{g})$$ $$\to$$ $$\text{SO}_{2}(\text{g})$$

This is then oxidised to sulfur trioxide ($$\text{SO}_{3}$$) using oxygen in the presence of a vanadium(V) oxide catalyst:

$$2\text{SO}_{2}(\text{g}) + \text{O}_{2}(\text{g})$$ $$\rightleftharpoons$$ $$2\text{SO}_{3}(\text{g})$$

Finally the sulfur trioxide is treated with water to produce sulfuric acid with a purity of $$\text{98}$$ – 99%:

$$\text{SO}_{3}(\text{g}) + \text{H}_{2}\text{O}(\text{l})$$ $$\to$$ $$\text{H}_{2}\text{SO}_{4}(\text{l})$$

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