Answer: MgSO 4 ·7H 2 O.
- A MgSO<sub>4</sub>·7H<sub>2</sub>O
- B CaSO<sub>4</sub>·2H<sub>2</sub>O
- C BaSO<sub>4</sub>
- D Na<sub>2</sub>SO<sub>4</sub>·10H<sub>2</sub>O
Correct answer: A. MgSO<sub>4</sub>·7H<sub>2</sub>O
Explanation: Epsom salt is magnesium sulfate heptahydrate (MgSO<sub>4</sub>·7H<sub>2</sub>O), 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.