Answer: NaOH and H2O2 (2Na2O2 + 2H2O → 4NaOH + O2).
- A NaOH and H2O2 (2Na2O2 + 2H2O → 4NaOH + O2)
- B Na2O and oxygen gas released without any hydroxide formed
- C NaOH alone, with no oxygen or peroxide byproduct at all
- D Na2CO3 and hydrogen peroxide formed via carbonation
Correct answer: A. NaOH and H2O2 (2Na2O2 + 2H2O → 4NaOH + O2)
Explanation: Na2O2 (sodium peroxide) reacts with water: 2Na2O2 + 2H2O → 4NaOH + O2. It is used in submarines as an O2 source.
Each s-block metal ion emits a characteristic flame colour because heating excites electrons to higher energy levels; light is emitted as they fall back, with the colour determined by the specific energy gap.
Concept context
Group 1 (alkali metals) and Group 2 (alkaline earth metals). Learn their reactions with water and air, important compounds like NaOH, Na₂CO₃, and CaCO₃, and anomalous behaviour of lithium and beryllium.