Question

Arsenic reacts with oxygen to form oxides analogous to the phosphorus oxides. These arsenic oxides react with water similarly to the phosphorus oxides. Write balanced chemical equations describing the reaction of arsenic with oxygen and the reaction of the oxides with water.

Short answer

The balanced equations for reaction of arsenic with oxygen is –

$$\begin{gathered} {\text{4As(s) + 3O}}_{\text{2}}\text{(g)}\to {\text{As}}_{\text{4}}{\text{O}}_{\text{6}}\text{(s)} \\ {\text{4As(s) + 5O}}_{\text{2}}\text{(g)}\to {\text{As}}_{\text{4}}{\text{O}}_{\text{10}}\text{(s)} \end{gathered}$$

The balanced equations for reaction of arsenic oxides with water is –

$$\begin{gathered} {\text{As}}_{\text{4}}{\text{O}}_{\text{6}}{\text{(s) + 6H}}_{\text{2}}\text{O(s)}\to {\text{4H}}_{\text{3}}{\text{AsO}}_{\text{3}}\text{(aq)} \\ {\text{As}}_{\text{4}}{\text{O}}_{\text{10}}{\text{(s) + 6H}}_{\text{2}}\text{O(s)}\to {\text{4H}}_{\text{3}}{\text{AsO}}_{\text{4}}\text{(aq)} \end{gathered}$$

Step-by-step solution

Concept Introduction

A chemical reaction in which the overall charge and the number of atoms for each element in the reaction are the same both sides.

Reaction of Arsenic with oxygen

The arsenic$\left(\text{III}\right)$oxide has the molecular formula${\text{As}}_{\text{4}}{\text{O}}_{\text{6}}$, with the same tetrahedral structure as${\text{P}}_{\text{4}}{\text{O}}_{\text{6}}$.

Arsenic also forms oxides with oxidation state $\text{+ 5}$, and these oxides have the molecular formula${\text{As}}_{\text{4}}{\text{O}}_{10}$.

These oxides are formed in the reaction of elemental arsenic and oxygen.

The balanced chemical equations describing the reactions of arsenic with oxygen are shown below.

$$\begin{gathered} {\text{4As(s) + 3O}}_{\text{2}}\text{(g)}\to {\text{As}}_{\text{4}}{\text{O}}_{\text{6}}\text{(s)} \\ {\text{4As(s) + 5O}}_{\text{2}}\text{(g)}\to {\text{As}}_{\text{4}}{\text{O}}_{\text{10}}\text{(s)} \end{gathered}$$

Therefore, the balanced equations are${\text{4As(s) + 3O}}_{\text{2}}\text{(g)}\to {\text{As}}_{\text{4}}{\text{O}}_{\text{6}}\text{(s)}$ and${\text{4As(s) + 5O}}_{\text{2}}\text{(g)}\to {\text{As}}_{\text{4}}{\text{O}}_{\text{10}}\text{(s)}$ .

 Step 3:Reaction of Oxides with water

The oxides shown above react with water to form the corresponding oxoacids.

The balanced chemical equations of oxoacid formation are shown below.

$$\begin{gathered} {\text{As}}_{\text{4}}{\text{O}}_{\text{6}}{\text{(s) + 6H}}_{\text{2}}\text{O(s)}\to {\text{4H}}_{\text{3}}{\text{AsO}}_{\text{3}}\text{(aq)} \\ {\text{As}}_{\text{4}}{\text{O}}_{\text{10}}{\text{(s) + 6H}}_{\text{2}}\text{O(s)}\to {\text{4H}}_{\text{3}}{\text{AsO}}_{\text{4}}\text{(aq)} \end{gathered}$$

Therefore, the balanced equations are${\text{As}}_{\text{4}}{\text{O}}_{\text{6}}{\text{(s) + 6H}}_{\text{2}}\text{O(s)}\to {\text{4H}}_{\text{3}}{\text{AsO}}_{\text{3}}\text{(aq)}$ and ${\text{As}}_{\text{4}}{\text{O}}_{\text{10}}{\text{(s) + 6H}}_{\text{2}}\text{O(s)}\to {\text{4H}}_{\text{3}}{\text{AsO}}_{\text{4}}\text{(aq)}$.