Question

Which of the following is a nitric acid anhydride?

• A. NO
• B. $NO_2$
• C. $N_2O_5$
• D. $N_2O_3$

Answer 1

Answer: (C)

$N_2O_5$

Answer 2

Dinitrogen pentaoxide (N20 5) is prepared by
dehydrating the concentrated nitric acid with
phosphorus pentoxide.
$4HNO_3 + P_4O_10 \longrightarrow 2N_2O_6 + +HPO_3$
So, $N_2O_5$ is regarded as anhydride of $HNO_3$.