Answer: It is insoluble and non-toxic, opaque to X-rays.
- A It is insoluble and non-toxic, opaque to X-rays
- B It is highly soluble, allowing rapid absorption into the bloodstream
- C It functions as an essential dietary nutrient for digestion
- D It readily dissolves upon contact with stomach acid
Correct answer: A. It is insoluble and non-toxic, opaque to X-rays
Explanation: BaSO<sub>4</sub> (barium meal) is insoluble in water and stomach acid, non-absorbable and safe; it scatters X-rays to show GI tract shape.
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.