Which one of the following oxides of nitrogen is known as ‘anhydride’ of nitric acid ?
N<sub>2</sub>O
N<sub>2</sub>O<sub>3</sub>
NO<sub>2</sub>
N<sub>2</sub>O<sub>5</sub>
Answer is Right!
Answer is Wrong!
This question was previously asked in
UPSC NDA-1 – 2016
The formula for nitric acid is HNO₃. Taking two molecules and removing one water molecule:
2HNO₃ → H₂N₂O₆
H₂N₂O₆ – H₂O → N₂O₅
Thus, N₂O₅ (dinitrogen pentoxide) is the anhydride of nitric acid. It reacts with water to form nitric acid: N₂O₅ + H₂O → 2HNO₃.
– To find the anhydride of an acid (like HNO₃), remove water molecule(s) from the acid formula while maintaining the correct ratio of other elements.
– N₂O₅ is dinitrogen pentoxide.