Number of oxygen atoms present in chemical formula of fuming sulphuric acid is .
Answer
7
Solution
Fuming sulphuric acid (oleum) is formed by dissolving SO3 in conc. H2SO4:
H2SO4 + SO3 H2S2O7 (pyrosulphuric acid)
∴ Number of O atoms in H2S2O7 = 7
Answer: 7