Answer: H 2 SO 4 with dissolved SO 3 (pyrosulfuric acid, H 2 S 2 O 7 ).
- A H<sub>2</sub>SO<sub>4</sub> with dissolved SO<sub>3</sub> (pyrosulfuric acid, H<sub>2</sub>S<sub>2</sub>O<sub>7</sub>)
- B Generally dilute aqueous H<sub>2</sub>SO<sub>4</sub> at low concentration
- C H<sub>2</sub>SO<sub>4</sub> existing largely as a gas under ordinary conditions
- D A direct mixture of concentrated H<sub>2</sub>SO<sub>4</sub> with concentrated HNO<sub>3</sub>
Correct answer: A. H<sub>2</sub>SO<sub>4</sub> with dissolved SO<sub>3</sub> (pyrosulfuric acid, H<sub>2</sub>S<sub>2</sub>O<sub>7</sub>)
Explanation: Oleum is formed when SO<sub>3</sub> is dissolved in concentrated H<sub>2</sub>SO<sub>4</sub>: SO<sub>3</sub> + H<sub>2</sub>SO<sub>4</sub> → H<sub>2</sub>S<sub>2</sub>O<sub>7</sub> (pyrosulfuric acid).
Xenon tetrafluoride (XeF4) has six electron domains around xenon — four Xe–F bonds plus two lone pairs. The lone pairs occupy opposite axial positions, leaving the four fluorine atoms in a square-planar shape (Xe–F ≈ 194 pm). Image: ChemSim, Public Domain, via Wikimedia Commons.
Concept context
Covers the nitrogen family (Group 15), oxygen family (Group 16), halogens (Group 17), and noble gases (Group 18). One of the highest-weightage inorganic chapters in NEET and JEE - includes preparation and properties of HNO₃, H₂SO₄, interhalogens, and xenon compounds.