Question

An alkali metal a gives a compound b(molecular mass=40)on reacting with water . The compound b gives a soluble compound c on treatment with aluminum oxide.Identify a, b and c

Answer 1

hello the alkali metal is sodium.

compound b is sodium hydroxide

NaOH+Al2O3=NaAlO2+H2O

where NaAlO2 is sodium aluminate

Answer 2

let

 the atomic weight of alkali metal A be x. When it reacts with water, it forms a compound B having molecular mass 40. Let the reaction be



According to the question,

x + 16 + 1 = 40 (Given)

x = 40-17 = 23

It is the atomic weight of Na (sodium).

Therefore, the alkali metal (A) is Na and the reaction is



So, compound B is sodium hydroxide (NaOH).

Sodium hydroxide reacts with aluminium oxide (Al2O3) to give sodium aluminate (NaAlO2). Thus, C is sodium aluminate (NaAlO2). The reaction involved is Al2O3