Answer: Self-contained breathing apparatus (reacts with CO2 and H2O to release O2).
- A Self-contained breathing apparatus (reacts with CO2 and H2O to release O2)
- B Nitrogen-based fertilisers applied directly to soil as widely reported
- C Explosive formulations requiring a stable oxidiser in standard practice
- D Soap manufacture through reaction with fatty acids under most conditions encountered
Correct answer: A. Self-contained breathing apparatus (reacts with CO2 and H2O to release O2)
Explanation: KO2 + H2O → KOH + H2O2 → O2 released; used in breathing masks and space capsules.
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.