A solid binary compound of oxygen and lead, \text{PbO}_2, reacts with concentrated hydroch… — JAMB UTME

A solid binary compound of oxygen and lead, $\text{PbO}_2$ , reacts with concentrated hydrochloric acid to yield lead(II) chloride, water, and chlorine gas, but fails to produce hydrogen peroxide when treated with cold dilute tetraoxosulfate(VI) acid. Based on this chemical behavior, which of the following statements correctly classifies $\text{PbO}_2$ and distinguishes it from a peroxide such as sodium peroxide ( $\text{Na}_2\text{O}_2$ )?

$\text{PbO}_2$ is a dioxide containing $\text{O}^{2-}$ ions with lead in the $+4$ oxidation state, whereas $\text{Na}_2\text{O}_2$ is a peroxide containing $\text{O}_2^{2-}$ ions.Answer
B
$\text{PbO}_2$ is an amphoteric oxide that acts purely as a neutral compound, whereas $\text{Na}_2\text{O}_2$ is an acidic anhydride.
C
$\text{PbO}_2$ is classified as a peroxide because its formula contains two oxygen atoms, whereas $\text{Na}_2\text{O}_2$ is a basic monoxide.
D
$\text{PbO}_2$ contains the $\text{O}_2^{2-}$ ion which oxidizes chloride ions to chlorine gas, whereas $\text{Na}_2\text{O}_2$ contains $\text{O}^{2-}$ ions.

Answer

Lead(IV) oxide (

\text{PbO}_2

) is classified as a dioxide containing

\text{O}^{2-}

ions with lead in the

+4

oxidation state, whereas sodium peroxide (

\text{Na}_2\text{O}_2

) is a peroxide containing the

\text{O}_2^{2-}

ion.

Lead(IV) oxide (

\text{PbO}_2

) is classified as a dioxide because it contains simple oxide ions (

\text{O}^{2-}

) with lead in the

+4

oxidation state. It acts as an oxidizing agent by reacting with concentrated

\text{HCl}

to liberate chlorine gas, but does not produce hydrogen peroxide when treated with cold dilute acids. In contrast, sodium peroxide (

\text{Na}_2\text{O}_2

) contains the peroxide ion (

\text{O}_2^{2-}

) and produces

\text{H}_2\text{O}_2

upon reaction with cold dilute acids.

Step-by-Step Solution

Analyze the structural difference between peroxides and dioxides.

Peroxides contain the peroxide anion

(\text{O}_2^{2-})

where oxygen has an oxidation state of

-1

. Dioxides contain standard oxide anions

(\text{O}^{2-})

where oxygen has an oxidation state of

-2

and the metal is in the

+4

oxidation state.

Chemical classification depends on the specific ionic species present in the oxide crystal lattice.

Evaluate the reaction of

\text{PbO}_2

with dilute acid.

\text{PbO}_2 + 2\text{H}_2\text{SO}_4 \rightarrow \text{Pb(SO}_4)_2 + 2\text{H}_2\text{O}

(no

\text{H}_2\text{O}_2

formed).

True peroxides yield hydrogen peroxide

(\text{H}_2\text{O}_2)

upon treatment with cold dilute acids, whereas dioxides do not.

Evaluate the reaction of

\text{PbO}_2

with concentrated hydrochloric acid.

\text{PbO}_2 + 4\text{HCl} \rightarrow \text{PbCl}_2 + 2\text{H}_2\text{O} + \text{Cl}_2\uparrow

The

\text{Pb}^{4+}

ion acts as an oxidizing agent, oxidizing

\text{Cl}^-

\text{Cl}_2

gas, confirming its behavior as a higher dioxide.

Key Concept

Distinction between Peroxides and Dioxides

Estimated Time:1m 30s

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