Question

An element reacts with Oxygen to form an oxide that dissolves in dilute Hydrochloric acid $\left(\mathrm{HCl}\right)$. The oxide formed also turns the red litmus blue. Is the element a metal or nonmetal?. Explain with a suitable example?

Answer 1

• Metals and non-metals generally reacts with Oxygen to form metal oxide.
• Since it is given in the question that oxide changes red litmus to blue then it indicates the oxide is basic in nature.
• Metal oxides are generally basic in nature.
• Thus, the element which forms an oxide and dissolves in dilute Hydrochloric acid$\left(\mathrm{HCl}\right)$ will be any metal.
• Further, as given in question when these metal oxides dissolve in dilute Hydrochloric acid$\mathbf{\left(}\mathbf{HCl}\mathbf{\right)}$ it forms metal chlorides.
• The chemical reaction of metal oxide with dilute Hydrochloric acid$\mathbf{\left(}\mathbf{HCl}\mathbf{\right)}$ produces salt and water

Showing an example to understand this concept more clearly.

• The chemical reaction that occurs between a metal say Magnesium and Oxygen produce Magnesium oxide$\left(\mathrm{MgO}\right)$ as follows:

$2\mathrm{Mg}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to \underset{\left(\mathrm{Magnesium}\mathrm{oxide}\right)}{2\mathrm{MgO}\left(\mathrm{s}\right)}$

• This produced Magnesium oxide reacts with Hydrochloric acid$\mathbf{\left(}\mathbf{HCl}\mathbf{\right)}$ to produce Magnesium chloride$\mathbf{\left(}{\mathbf{MgCl}}_{\mathbf{2}}\mathbf{\right)}$ and water as follows:

$\underset{(\mathrm{Magnesium}\mathrm{oxide})}{\mathrm{MgO}\left(\mathrm{s}\right)}+\underset{(\mathrm{Hydrochloric}\mathrm{acid})}{2\mathrm{HCl}\left(\mathrm{aq}\right)}\to \underset{(\mathrm{Magnesium}\mathrm{Chloride})}{{\mathrm{MgCl}}_2\left(\mathrm{aq}\right)}+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Hence, we conclude that the element which forms oxide is metal which reacts with dilute Hydrochloric to form metal chlorides.

Also, the oxide is basic in nature as it changes red litmus to blue