Question

Non-metallic oxides are:
(A) Acidic in nature
(B) Amphoteric in nature
(C) Basic in nature
(D) None of these

Answer 1

Hint: Non-metal oxides such as sulphur dioxide and nitrogen oxide are responsible for acid rain. Using this application of non-metal oxides, try and determine their nature.

Step-by-Step Solution:
Let us first analyse what non-metallic oxides really are before moving on towards the specifics of this question.
All non-metals form covalent oxides with oxygen, which react with water to form acids or with bases to form salts. Most non-metal oxides are acidic and form oxyacids, which in turn yield hydronium ions (\[{{H}_{3}}{{O}^{+}}\]) in aqueous solution. There are two general statements that describe the behaviour of acidic oxides. First, oxides such as sulphur trioxide (\[S{{O}_{3}}\]) and dinitrogen pentoxide (\[{{N}_{2}}{{O}_{5}}\]), in which the non-metal exhibits one of its common oxidation numbers, are known as acid anhydrides. These oxides react with water to form oxyacids, with no change in the oxidation number of the non-metal; for example,
\[{{N}_{2}}{{O}_{5}}~+\text{ }{{H}_{2}}O\to 2HN{{O}_{3}}\]
The non-metal oxides can be neutralized with a base to form salt and water.
\[Non-Metal\text{ }Oxide\text{ }+\text{ }Base~\to ~Salt\text{ }+\text{ }Water\]
For example,
$\begin{matrix}
   S{{O}_{3(g)}}~+\text{ }Ba{{\left( OH \right)}_{2(aq)}}~\to ~BaS{{O}_{4(aq)}}~+\text{ }{{H}_{2}}{{O}_{(l)}} \\
   {{P}_{4}}{{O}_{10(s)}}~+\text{ }12\text{ }NaO{{H}_{(aq)}}~\to ~4\text{ }N{{a}_{3}}P{{O}_{4(aq)}}~+\text{ }6\text{ }{{H}_{2}}{{O}_{(l)}} \\
\end{matrix}$

Generally, the more metallic character an element has, the more basic its oxide will be. Likewise, the more non-metallic character an element has, the more acidic its oxide will be. The non-metallic character of an element can be determined by its position on the periodic table:



Therefore, per our analysis, the answer to this question is a) Acidic in nature

Note: Most non-metal oxides are acidic, but not all. For example, carbon monoxide (CO) is not acidic.
The addition of water to a non-metal oxide results in a compound that consists of a non-metal atom surrounded by oxo (=O) and hydroxy (-OH) groups. For example,
\[S{{O}_{3\left( l \right)}}\text{ }+\text{ }{{H}_{2}}{{O}_{\left( l \right)}}\text{ }\to \text{ }{{H}_{2}}S{{O}_{4\left( l \right)}}\]