Answer: with both acids and bases.
- A only with acids
- B only with bases
- C with both acids and bases
- D with neither acids nor bases
Correct answer: C. with both acids and bases
Explanation: Being amphoteric, Al₂O₃ dissolves in acids (forming Al³⁺ salts) and in alkalis (forming aluminates).
Diamond's rigid 3D tetrahedral network makes it the hardest natural material, while graphite's flat hexagonal sheets are held together only by weak forces, letting them slide past each other (used as a lubricant and in pencils).
Concept context
Covers the Boron family (Group 13: B, Al) and the Carbon family (Group 14: C, Si, Ge, Sn, Pb). Key topics include Lewis acid behaviour of BF₃, borax bead test, silicates, silicones, allotropes of carbon, and trends in properties down the group.