Question

The valency of phosphorous is five, then the molecular formula of oxide of phosphorous is _________ .

• A. $P{O}_5$
• B. $P_2{O}_5$
• C. $P_5{O}_2$
• D. none of these

Answer 1

Answer: (B)

$P_2{O}_5$

The valency of phosphorous is five and the valence of oxygen is two. Two phosphorous atoms will combine with five oxygen atoms. Then the molecular formula of oxide of phosphorous is $P_2{O}_5$.

Note: If the valency of phosphorous was three, then the molecular formula of oxide of phosphorous will be $P_2{O}_3$.