Question

Question: Identify each of the following oxides as an acid or base anhydride. Write the chemical formula and give the name of the acid or base formed upon reaction with water.

$$\begin{gathered} \mathbf{\text{(a)MgO}} \\ {\mathbf{\text{(b)Cl}}}_{\mathbf{\text{2}}}\mathbf{\text{O}} \\ {\mathbf{\text{(c)SO}}}_{\mathbf{\text{3}}} \\ {\mathbf{\text{(d)Cs}}}_{\mathbf{\text{2}}}\mathbf{\text{O}} \end{gathered}$$

Short answer

$$\begin{gathered} \text{(a) MgO}\to \text{Basic Anhydride} \\ {\text{(b) Cl}}_{\text{2}}\text{O}\to \text{Acidic Anhydride} \\ {\text{(c) SO}}_{\text{3}}\to \text{Acidic Anhydride} \\ {\text{(d) Cs}}_{\text{2}}\text{O}\to \text{Basic Anhydride} \end{gathered}$$

and,

$$\begin{gathered} \left(\text{a}\right)\text{Base}\to {\text{Mg(OH)}}_2 \\ \text{(b)Acid}\to \text{HClO} \\ \text{(c) Acid}\to {\text{H}}_{\text{2}}{\text{SO}}_{\text{4}} \\ \left(\text{d}\right)\text{Base}\to \text{CsOH} \end{gathered}$$

Step-by-step solution

Understanding the concept of acid and base anhydride

By withdrawing water from an oxoacid until only the oxide remains, an acid anhydride is formed and a base anhydride is formed when water is removed from metallic hydroxides.

$$\begin{gathered} \mathbf{Oxoacid}\mathbf{-}\mathbf{water}\mathbf{=}\mathbf{acidanhydride} \\ \mathbf{Metalichydroxide}\mathbf{-}\mathbf{water}\mathbf{=}\mathbf{baseanhydide} \end{gathered}$$

Applying the concept

(a) Here, magnesium oxide ( MgO) is basic anhydride as it is derived from metallic hydroxide ${\text{Mg(OH)}}_2$

${\text{MgO +H}}_{\text{2}}\text{O}\to {\text{Mg(OH)}}_{\text{2}}$

(b) Dichloride monoxide ${\mathrm{Cl}}_2\mathrm{O}$ is the acidic anhydride as it is derived from oxoacid HClO

${\text{Cl}}_{\text{2}}{\text{O +H}}_{\text{2}}\text{O}\to \text{2HClO}$

(c) Sulphur trioxide ${\mathrm{SO}}_3$is the acidic anhydride as it is derived from oxoacid ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$

${\text{SO}}_{\text{3}}{\text{+H}}_{\text{2}}\text{O}\to {\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$

(d) Cesium oxide ${\text{Cs}}_{\text{2}}\text{O}$is the basic anhydride as is it derived from the metallic hydroxide of CsOH

${\text{Cs}}_{\text{2}}{\text{O +H}}_{\text{2}}\text{O}\to \text{2CsOH}$