Question

Which of the following oxides is neutral in nature?
A. $SrO$
B. $A{l_2}{O_3}$
C. $C{O_2}$
D. $CO$

Answer 1

Hint: Neutral oxides are the oxides which show neither acidic properties nor basic properties when they react with water. So write the reactions of the given compounds with water to know which one is a neutral oxide. An acid reacts with a base to form salt and water. To find whether the given options react with a base or an acid.

Complete step by step answer:
We are given four compounds and we have to find which of these a neutral oxide is.
The first one is $SrO$. $SrO$ is called strontium oxide or strontia. It reacts with water to form Strontium hydroxide. It reacts with an acid to form a salt.
$SrO + {H_2}O \to Sr{\left( {OH} \right)_2}$
Therefore, $SrO$ is basic in nature and is a basic oxide.
Second one is $A{l_2}{O_3}$. $A{l_2}{O_3}$ is called Aluminum oxide. Aluminum is an amphoteric oxide, which means it shows both acidic and basic characters. Acid and base react to form salt and water. So Aluminum oxide can be used as a base and as well as an acid to form salts.
 Aluminum oxide reacts with water to form Aluminum hydroxide.
$A{l_2}{O_3} + 3{H_2}O \to 2Al{\left( {OH} \right)_3}$
Aluminum is a both acidic and basic oxide.
Third one is $C{O_2}$. $C{O_2}$ is called carbon dioxide. Carbon dioxide is a Lewis acid. It reacts with water to form carbonic acid.
$C{O_2} + {H_2}O \to {H_2}C{O_3}$
$C{O_2}$ is an acidic oxide.
The fourth one is $CO$. $CO$ is called carbon monoxide. Carbon monoxide is slightly soluble in water. The physical properties of $CO$ resemble the physical properties of Nitrogen. $CO$ does not react with an acid or a base. It is, therefore, neutral in nature.

The neutral oxide is Carbon monoxide $CO$, Option D is correct.

Note:
Here $CO$ is soluble in water but it is a neutral oxide because it does not form any acid or any base when reacted with water rather it forms Carbon dioxide. So for oxide to be acidic or basic, it should form an acid or a base when reacted with water, or it should form a salt when reacted with an acid or a base.