Lithium only forms monoxide when heated in oxygen. Sodium forms monoxide and peroxide in excess of oxygen. Other alkali metals form superoxide with oxygen i.e. MO2.

Question

Lithium only forms monoxide when heated in oxygen. Sodium forms monoxide and peroxide in excess of oxygen. Other alkali metals form superoxide with oxygen i.e. MO₂.

The abnormal behavior of Lithium is due to small size. The larger size of alkali metals has tendency to form super oxides.

The three ions are related to each other as follows —

All the three ions abstract proton from water.

(Q1)→Consider the following reaction

M + O₂ → MO₂ (M –alkali metal)

Select the correct statements :

(A) M will not be Li and Na

(C) M will not be Rb

(B) M will not be Cs & Rb

(D) M will not be K

(Q2) →Which compound will liberate oxygen when reacted with water :

(A) Na₂O₂

(B) KO₂

(C) Na₂O

(D) Cs₂O₂

Answer 1

Ans —

Q1 →Correct statement is (A) M will not be Li and Na.

Q2 → KO₂ will liberate oxygen when reacted with water. So, The correct option is (B).