Q14.94P - Chemistry: Molecular Nature Of Matter And Change

Question

Rank the following oxides in order of increasing acidity in water: ${\mathbf{Sb}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{3}}$, ${\mathbf{Bi}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{3}}$, ${\mathbf{P}}_{\mathbf{4}}{\mathbf{O}}_{\mathbf{10}}$, ${\mathbf{Sb}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{5}}$ .

Step-by-Step Solution

Answer

${\mathrm{Bi}}_2{\mathrm{O}}_3<{\mathrm{Sb}}_2{\mathrm{O}}_3<{\mathrm{Sb}}_2{\mathrm{O}}_5<{\mathrm{P}}_4{\mathrm{O}}_{10}$

Step 1: Group 15 elements

Group 15 elements belonging to the nitrogen family. They include nitrogen, phosphorus, arsenic, antimony, bismuth, and moscovium.

The atomic number of the group 15 elements is as follows;

Nitrogen (N) = 7

Phosphorus (P) = 15

Arsenic (As) = 33

Antimony (Sb) = 51

Bismuth (Bi) = 83

Step 2: Acidity of elements of group 15

As we move down the group, the atomic number increase. In a group electronegativity decreases and metallic character increases as we move down. So that acidic character also decreases down the group. Hence among the four ${\mathrm{P}}_4{\mathrm{O}}_{10}$ is the most acidic one and as present at the bottom so it is less acidic.

For the different oxides of the same element acidity increase with an increase in the oxidation state. For ${\mathrm{Sb}}_2{\mathrm{O}}_5$ oxidation state  of Sb is +5 while for ${\mathrm{Sb}}_2{\mathrm{O}}_3$ oxidation state Sb of is +3. Hence ${\mathrm{Sb}}_2{\mathrm{O}}_5$ is more acidic than $S{b}_2{O}_3$ .

${\mathrm{Bi}}_2{\mathrm{O}}_3<{\mathrm{Sb}}_2{\mathrm{O}}_3<{\mathrm{Sb}}_2{\mathrm{O}}_5<{\mathrm{P}}_4{\mathrm{O}}_{10}$