Sodium metal reacts with excess oxygen gas at elevated temperatures to produce sodium pero… — JAMB UTME

Sodium metal reacts with excess oxygen gas at elevated temperatures to produce sodium peroxide ( $\text{Na}_2\text{O}_2$ ). What is the oxidation state of oxygen in sodium peroxide?

$-1$ Answer
B
$-2$
C
$0$
D
$+1$

Answer

The oxidation state of oxygen in sodium peroxide (

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

) is

-1

In sodium peroxide (

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

), the two sodium ions contribute a total charge of

+2

. To maintain electrical neutrality, the two oxygen atoms balance this with a total charge of

-2

, giving each oxygen atom an oxidation state of

-1

Step-by-Step Solution

Assign the known oxidation state for sodium in its compounds.

Sodium (

\text{Na}

) is an alkali metal (Group 1) and always has an oxidation state of

+1

in compounds.

Alkali metals lose one valence electron to achieve a stable noble gas electron configuration.

Set up the oxidation state equation for the neutral molecule

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

2(+1) + 2(x) = 0

, where

x

represents the oxidation state of oxygen.

The algebraic sum of oxidation numbers in a neutral compound must equal zero.

Solve for

x

+2 + 2x = 0 \implies 2x = -2 \implies x = -1

Algebraic evaluation yields the oxidation number for each oxygen atom.

Key Concept

Oxidation Numbers of Oxygen in Alkali Metal Peroxides

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