Question

Phosphoric acid is formed when phosphorus pentoxide reacts with ______.

• A. hydrogen
• B. alcohol
• C. water
• D. nitrogen

Answer 1

The correct option is C water

Phosphoric acid $\left(H_{3}P{O}_4\right)$ is formed when phosphorus pentoxide$\left(P_2{O}_5\right)$ reacts with water $\left(H_{2}O\right)$.

Phosphorus pentoxide is a non-metallic oxide, and when non-metallic oxides react with water, acid is formed. These acids undergo dissociation to form hydrogen ion $H^{+}$ and an anion which is stabilized by oxygen and non-metallic element.

These kind of acids are known as oxyacids, since they have oxygen in them. Phosphoric acid is formed in the following way-

$P_2{O}_5+3H_{2}O\to 2H_{3}P{O}_4$

Hence, the correct answer is option (C).