Question

Which of the following is/are neutral oxide?
(This question has multiple correct options)
(a) CO
(b) ZnO
(c) ${ N }_{ 2 }O$
(d) $Sn{ O }_{ 2 }$

Answer 1

Hint: Oxides are binary compounds of oxygen and an element. These oxides can be acidic, basic, amphoteric and neutral in nature. The neutral oxides do not possess any acidic or basic properties.

Complete answer:
First let us understand oxides. When an element reacts with oxygen to form a binary compound consisting of oxygen and the element, such compounds are called oxides. Examples: CaO, ZnO, $ C{ O }_{ 2 }$, $ { H }_{ 2 }O$ etc.
These oxides can be acidic, basic, amphoteric and neutral in nature.

Acidic oxides: When these oxides are dissolved in water they give acids. These oxides are generally the oxides of non-metals. Some examples are shown below:
$ \begin{matrix} { SO }_{ 2 }(g) \\ Sulphur\quad dioxide \end{matrix}+\begin{matrix} { H }_{ 2 }O(l) \\ Water \end{matrix}\rightarrow \begin{matrix} { H }_{ 2 }{ SO }_{ 3 }(aq) \\ Sulfurous\quad acid \end{matrix}$
$ \begin{matrix} { CO }_{ 2 }(g) \\ Carbon\quad dioxide \end{matrix}+\begin{matrix} { H }_{ 2 }O(l) \\ Water \end{matrix}\rightarrow \begin{matrix} { H }_{ 2 }{ CO }_{ 3 }(aq) \\ Carbonic\quad acid \end{matrix}$

Basic oxides: When these oxides are dissolved in water they give bases. These oxides are generally the oxides of group 1 and group 2 elements. Some examples are shown below:
$ \begin{matrix} CaO(s) \\ Calcium\quad oxide \end{matrix}+\begin{matrix} { H }_{ 2 }O(l) \\ Water \end{matrix}\rightarrow \begin{matrix} Ca{ OH }_{ 2 }(aq) \\ Calcium\quad hydroxide \end{matrix}$
$ \begin{matrix} { Na }_{ 2 }O(s) \\ Sodium\quad oxide \end{matrix}+\begin{matrix} { H }_{ 2 }O(l) \\ Water \end{matrix}\rightarrow \begin{matrix} 2NaOH(aq) \\ Sodium\quad hydroxide \end{matrix}$

Amphoteric oxides: These oxides can react both as an acid and as a base. Therefore when they react with a base they form salt and water (neutralisation reaction). Similarly on reaction with an acid they form salt and water. Some of the examples are shown below:
$ \begin{matrix} ZnO(s) \\ Zinc\quad oxide \end{matrix}+\begin{matrix} 2HCl(aq) \\ Hydrochloric\quad acid \end{matrix}\rightarrow \begin{matrix} { ZnCl }_{ 2 }(aq) \\ Zinc\quad Chloride(salt) \end{matrix}+\begin{matrix} { H }_{ 2 }O \\ Water \end{matrix}$
$ \begin{matrix} ZnO(s) \\ Zinc\quad oxide \end{matrix}+\begin{matrix} 2NaOH(aq) \\ Sodium\quad hydroxide \end{matrix}\rightarrow \begin{matrix} { Na }_{ 2 }{ ZnO }_{ 2 }(aq) \\ Sodium\quad Zincate(salt) \end{matrix}+\begin{matrix} { H }_{ 2 }O \\ Water \end{matrix}$
Similarly (d) $Sn{ O }_{ 2 }$ is also an amphoteric oxide.

Neutral oxides: They do not have acidic or basic properties. They do not form salts like amphoteric oxides on reaction with an acid or a base. Examples: CO and ${ N }_{ 2 }O$. Both of these are only slightly soluble in water.
So, the correct answer is “Option A and C”.

Note: Do not get confused between amphoteric oxides and neutral oxides. While amphoteric oxides react with both acids and bases, neutral oxides don’t. Also remember that acidic oxides are also called acid anhydrides since they react with water to give acids. If acidic oxides are reacted with bases they would undergo neutralisation reaction and produce salt and water. Similarly basic oxides are called basic anhydrides.