Answer: Historical preparation of H2O2: BaO2 + H2SO4 → BaSO4 + H2O2.
- A Historical preparation of H2O2: BaO2 + H2SO4 → BaSO4 + H2O2
- B The electrolytic production of elemental barium metal
- C The direct chemical reduction of barium sulfate to barium sulfide
- D The industrial Solvay process for manufacturing sodium carbonate
Correct answer: A. Historical preparation of H2O2: BaO2 + H2SO4 → BaSO4 + H2O2
Explanation: Before modern methods, H2O2 was made by treating BaO2 with cold dilute H2SO4, giving insoluble BaSO4 precipitate and H2O2 solution.
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.