Question

Phosphorus has valencies of 3 and 5. What is the formula of the two oxides of phosphorus?

Answer 1

We know that phosphorus is a chemical element denoted with the symbol P and has atomic number 15. Elemental phosphorus appears in two main forms, white phosphorus and red phosphorus. It is highly reactive, and phosphorus does not exist as a free element on Earth.

Complete step by step answer: Let us consider X as an element. So, the valency of X will be +3 and the valency of oxide will be -2. The formula of the oxide would be ${X_2}{O_3}$. The oxide of phosphorus that exists in ${X_2}{O_3}$ is phosphorus trioxide, whose chemical formula can be written as ${P_2}{O_3}$.
Phosphorus trioxide is the chemical compound that has an empirical formula of ${P_2}{O_3}$and the molecular formula is ${P_4}{O_6}$. We can otherwise be called tetraphosphorus hexoxide. The anhydride of phosphorous acid is phosphorus trioxide. We can prepare phosphorus trioxide by the combustion of phosphorus in a controlled supply of oxygen at lower temperatures.
We can write the chemical equation as,
${P_4} + 3{O_2}\xrightarrow{{}}{P_4}{O_6}$
If the valency of X is +5 and valency of oxide will be -2. The formula of the oxide would be ${X_2}{O_5}$. The oxide of phosphorus that exists in ${X_2}{O_5}$ is phosphorus trioxide, whose chemical formula can be written as ${P_2}{O_5}$.
We must know that the ${P_2}{O_5}$ is the empirical formula of Phosphorus pentoxide and the molecular formula is ${P_4}{O_{10}}$. The acid anhydride of phosphoric acid is phosphorus pentoxide. We can use it as dehydrating agent and desiccant,
We can prepare phosphorus pentoxide by burning elemental phosphorus in enough oxygen. We can write the chemical equation as,
${P_4} + 5{O_2}\xrightarrow{{}}{P_4}{O_{10}}$

Note: We know that the phosphorus pentoxide is a white solid and does not contain any odour. The molar mass of phosphorus pentoxide is $283.9{\text{ }}g/mol$. When Phosphorus pentoxide undergoes hydrolysis with water and this reaction is highly exothermic. It is an important component of the Onodera reagent that is used in the oxidation of alcohols. We can use phosphorus pentoxide in some organic synthesis reactions. We can use it in the preparation of nitriles from primary amides. We can use phosphorus trioxide as a ligand.