Question

(i) When alkali metals are heated in excess of air. What is the nature of oxides formed? 

(ii) How can you prepare baking soda? 

(iii) Which is more reducing, alkali metals or alkaline earth metals? 

(iv) Alkaline earth metals impact a characteristic colour to the flame but be and Mg do not, why? 

(v) Write general configuration of alkali and alkaline earth metals.

Answer 1

(i) When heated with excess of air, lithium forms normal oxide, Li₂O sodium forms peroxide, Na₂O₂ , whereas potassium, rubidium and caesium form superoxide’s having general formula MO₂.

4Li + O₂ → 2Li₂O

2Na + O₂ → Na₂O₂

K + O₂ → KO₂

(ii) Baking soda: It is prepared commercially by dissolving soda ash in water and treating with carbon dioxide.

Na₂CO₃ + CO₂ + H₂O → 2NaHCO₃

(iii) Alkali metals are more reducing than alkaline earth metals because of low ionisation energy.

(iv) Alkaline earth metals impart colour to flame but be and Mg do not, because they do not have unpaired electrons for excitation.

(v) Alkali metals ns¹

Alkaline earth metals ns²