Write the Formula of Pyrosulphuric Acid

The chemical formula of Pyrosulphuric acid (also known as oleum) is H₂S₂O₇. It is made by combining sulfur trioxide (SO₃) with sulfuric acid (H₂SO₄). Pyrosulphuric acid contains two sulfur atoms and seven oxygen atoms along with two hydrogens. It is a strong acid used in industrial processes, especially for sulfonation and as a dehydrating agent. The other options like H₂SO₅ or H₂S₂O₈ refer to different sulfur-oxygen compounds, but only H₂S₂O₇ is pyrosulphuric acid.