Question

Answer the following question:
An element X on reacting with oxygen forms an oxide X₂O. This oxide dissolves in water and turns red litmus blue. State whether element X is metal or a non - metal. Explain with a proper example. 

Answer 1

X is a metal like Na or K.

Sodium combines with oxygen, forms sodium oxide (Na₂O). Sodium oxide dissolves in water and forms an alkali, sodium hydroxide (NaOH). In sodium hydroxide, red litmus turns blue.

\[\ce{\underset{\text{Sodium}}{2Na} + \underset{\text{Oxygen}}{O2} -> \underset{\text{Sodium Oxide}}{Na2O}}\]

\[\ce{\underset{\text{Sodium Oxide}}{Na2O} + \underset{\text{Water}}{H2O} -> \underset{\text{Sodium hydroxide}}{2NaOH}}\]