Chapter 16, Problem 108QP

Interpretation Introduction

Interpretation:

Each of the given species are to be classified as acidic, basic, or amphoteric.

Concept Introduction:

Elements combine with oxygen atom(s) to form oxides. They, then, react with water to either produce an acid or a base.

In their low oxidation number, all alkali and alkaline metal oxides are basic in nature.

Some metal oxides, in a high oxidation state, show acidic behavior.

All nonmetal oxides are acidic in nature in their highest oxidation state. They are considerably neutral in their low oxidation state. In any case, nonmetal oxides do not show a basic nature.

Metallic oxides show acidic as well as basic natures, according to the reaction conditions. These are called amphoteric oxides.

Answer to Problem 108QP

Solution:

(a)

Acidic

(b)

Basic

(c)

Basic

(d)

Acidic

(e)

Neutral

(f)

Neutral

(g)

Amphoteric

(h)

Acidic

(i)

Amphoteric

(j)

Basic

Explanation of Solution

a) ${\text{CO}}_2$

The species ${\text{CO}}_2$ is an oxide of a nonmetal, and carbon $\left(\text{C}\right)$ is present in its highest oxidation state. The reaction of ${\text{CO}}_2$ with water is

${\text{CO}}_2{}_{\left(\text{g}\right)}+{\text{H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}\rightleftharpoons {\text{H}}_2{\text{CO}}_3{}_{\left(\text{aq}\right)}$

Thus, ${\text{CO}}_2$ is an acidic oxide.

b) ${\text{K}}_2\text{O}$

The species ${\text{K}}_2\text{O}$ is an oxide of a metal, and potassium $\left({\text{K}}^{+}\right)$ is a stable ion that forms an ionic bond with oxygen, due to which ${\text{O}}^{2-}$ can react with water. The reaction of ${\text{K}}_2\text{O}$ with water is

${\text{K}}_2{\text{O}}_{\left(\text{s}\right)}+{\text{H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}\rightleftharpoons 2{\text{KOH}}_{\left(\text{aq}\right)}$

Thus, ${\text{K}}_2\text{O}$ is a basic oxide.

c) $\text{CaO}$

The species $\text{CaO}$ is an oxide of a metal, and calcium $\left({\text{Ca}}^{2+}\right)$ is a stable ion that forms an ionic bond with oxygen, due to which ${\text{O}}^{2-}$ can react with water. The reaction of $\text{CaO}$ with water is

${\text{CaO}}_{\left(\text{s}\right)}+{\text{H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}\rightleftharpoons \text{Ca}{\left(\text{OH}\right)}_2{}_{\left(\text{aq}\right)}$

Thus, $\text{CaO}$ is a basic oxide.

d) ${\text{N}}_2{\text{O}}_5$

The species ${\text{N}}_2{\text{O}}_5$ is an oxide of a nonmetal, and nitrogen $\left(\text{N}\right)$ is present in its highest oxidation state. The reaction of ${\text{N}}_2{\text{O}}_5$ with water is

${\text{N}}_2{\text{O}}_5{}_{\left(\text{g}\right)}+{\text{H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}\rightleftharpoons 2{\text{HNO}}_3{}_{\left(\text{aq}\right)}$

Thus, ${\text{N}}_2{\text{O}}_5$ is an acidic oxide.

e) $\text{CO}$

The species $\text{CO}$ is an oxide of a nonmetal, and carbon $\left(\text{C}\right)$ is not present in its highest oxidation state. The reaction of $\text{CO}$ with water is

${\text{CO}}_{\left(\text{g}\right)}+{\text{H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}\rightleftharpoons {\text{H}}_2{}_{\left(\text{g}\right)}+{\text{CO}}_2{}_{\left(\text{g}\right)}$

There is neither an acid nor a base formed by this reaction. Thus, $\text{CO}$ is a neutral oxide.

f) $\text{NO}$

The species $\text{NO}$ is an oxide of a nonmetal, and nitrogen $\left(\text{N}\right)$ is not present in its highest oxidation state. The reaction of $\text{NO}$ with water cannot take place without the presence of oxygen.

Thus, $\text{NO}$ is a neutral oxide.

g) ${\text{SnO}}_2$

The species ${\text{SnO}}_2$ is an oxide of a metalloid. It shows acidic as well as basic behavior, according to the reaction conditions.

The reaction of ${\text{SnO}}_2$ with an acid $\left(\text{HCl}\right)$ is

$\begin{array}{l}{\text{SnO}}_2{}_{\left(\text{s}\right)}+4{\text{HCl}}_{\left(\text{aq}\right)}\rightleftharpoons {\text{SnCl}}_4{}_{\left(\text{aq}\right)}+2{\text{H}}_2{\text{O}}_{\left(\text{l}\right)}\\ \text{Base Acid Salt Water}\end{array}$

With a base $\left(\text{NaOH}\right)$, ${\text{SnO}}_2$ reacts as:

$\begin{array}{l}{\text{SnO}}_2{}_{\left(\text{s}\right)}+2{\text{NaOH}}_{\left(\text{aq}\right)}\rightleftharpoons {\text{Na}}_2{\text{SnO}}_2{}_{\left(\text{aq}\right)}+{\text{H}}_2{\text{O}}_{\left(\text{l}\right)}\\ \text{Acid Base Salt Water}\end{array}$

Thus, ${\text{SnO}}_2$ is an amphoteric oxide.

h) ${\text{SO}}_3$

The species ${\text{SO}}_3$ is an oxide of a nonmetal, and sulfur $\left(\text{S}\right)$ is present in its highest oxidation state. The reaction of ${\text{SO}}_3$ with water is

${\text{SO}}_3{}_{\left(\text{g}\right)}+{\text{H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}\rightleftharpoons {\text{H}}_2{\text{SO}}_4{}_{\left(\text{aq}\right)}$

Thus, ${\text{SO}}_3$ is an acidic oxide.

i) ${\text{Al}}_2{\text{O}}_3$

The species ${\text{Al}}_2{\text{O}}_3$ is an oxide of a metal, where aluminum is not in its highest oxidation state. It shows acidic as well as basic behavior, according to the reaction conditions.

The reaction of ${\text{Al}}_2{\text{O}}_3$ with an acid $\left(\text{HCl}\right)$ is

$\begin{array}{l}{\text{Al}}_2{\text{O}}_3{}_{\left(\text{s}\right)}+6{\text{HCl}}_{\left(\text{aq}\right)}\rightleftharpoons 2{\text{AlCl}}_3{}_{\left(\text{aq}\right)}+3{\text{H}}_2{\text{O}}_{\left(\text{l}\right)}\\ \text{Base Acid Salt Water}\end{array}$

With a base $\left(\text{NaOH}\right)$, ${\text{Al}}_2{\text{O}}_3$ reacts as:

$\begin{array}{l}{\text{Al}}_2{\text{O}}_3{}_{\left(\text{s}\right)}+2{\text{NaOH}}_{\left(\text{aq}\right)}+3{\text{H}}_2{\text{O}}_{\left(\text{l}\right)}\rightleftharpoons 2\text{NaAl}{\left(\text{OH}\right)}_4{}_{\left(\text{aq}\right)}\\ \text{Acid Base Salt }\end{array}$

In this reaction ${\text{Al}}_2{\text{O}}_3$ acts as an acid and neutralizes the base to produce a salt. Thus, ${\text{Al}}_2{\text{O}}_3$ is considered to be an acid.

Therefore, ${\text{Al}}_2{\text{O}}_3$ is an amphoteric oxide.

j) $\text{BaO}$

The species $\text{BaO}$ is an oxide of a metal, and Barium $\left({\text{Ba}}^{2+}\right)$ is a stable ion that forms an ionic bond with oxygen, due to which ${\text{O}}^{2-}$ can react with water. The reaction of $\text{BaO}$ with water is

${\text{BaO}}_{\left(\text{s}\right)}+{\text{H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}\rightleftharpoons \text{Ba}{\left(\text{OH}\right)}_2{}_{\left(\text{aq}\right)}$

Thus, $\text{BaO}$ is a basic oxide.