Question

Identify the correct formula of 'oleum' from the following:

Options

• H₂S₂O₈

• H₂S₂O₇

• H₂SO₃

• H₂SO₄

Answer 1

H₂S₂O₇

Explanation:

Oleum is formed when sulphur trioxide (SO₃) is dissolved in concentrated sulphuric acid (H₂SO₄). This compound is also called fuming sulphuric acid and can be diluted with water to obtain sulphuric acid of the desired concentration.

So, the reaction is:

\[\ce{H2SO4 + SO3 -> H2S2O7}\]