Question

The main oxides formed on combustion of $Li, Na$ and $K$ in excess of air are, respectively :

• A. $Li_2O, Na_2O$ and $KO_2$
• B. $LiO_2, Na_2O_2$ and $K_2O$
• C. $Li_2O_2, Na_2O_2 $ and $KO_2$
• D. $Li_2O, Na_2O$ and $ KO_2$

Answer 1

The Correct Option is C

Let's examine the question regarding the oxides formed by the elements Lithium (Li), Sodium (Na), and Potassium (K) when they undergo combustion in excess of air. These elements are part of the alkali metals group, and their oxides exhibit specific characteristics:

1. Lithium (Li):
   • Lithium, when burned in the presence of excess air, forms Lithium oxide (Li_2O).
2. Sodium (Na):
   • Sodium reacts with excess air to primarily form Sodium peroxide (Na_2O_2).
3. Potassium (K):
   • When Potassium combusts in excess air, it forms Potassium superoxide (KO_2).

Based on the above understanding:

• The oxides formed by Lithium, Sodium, and Potassium are Li_2O, Na_2O_2, and KO_2 respectively.
• Therefore, the correct answer is: Li_2O_2, Na_2O_2, and KO_2.

To further clarify, different alkali metals form different oxides due to variations in their chemical reactivity and oxidation states under different conditions:

• Li: Mostly forms simple oxides.
• Na: Has a tendency to form peroxides due to its reactivity level in excess air.
• K: Forms superoxides, which result from its higher reactivity compared to Li and Na.

In summary, the recognition of these oxide formation pathways aligns with the typical behavior observed in the alkali metals group.