Phosphorus pentoxide reacts with nitric acid to form.

Explanation

To solve the question about the reaction of phosphorus pentoxide with nitric acid, we can follow these steps:

### Step 1: Identify the Reactants
The reactants in this reaction are phosphorus pentoxide (P4O10) and nitric acid (HNO3).

### Step 2: Understand the Properties of Phosphorus Pentoxide
Phosphorus pentoxide is known to be a powerful dehydrating agent and has a strong affinity for water. This property will influence its reaction with nitric acid.

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