Answer: MgSO4·7H2O.
- A MgSO4·7H2O
- B CaSO4·2H2O
- C BaSO4
- D Na2SO4·10H2O
Correct answer: A. MgSO4·7H2O
Explanation: Epsom salt is magnesium sulfate heptahydrate (MgSO4·7H2O), used as a laxative and in bath salts.
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.