Answer: accepts OH⁻ from water.
- A donates one proton directly
- B releases three protons in water
- C is fully ionised in water
- D accepts OH⁻ from water
Correct answer: D. accepts OH⁻ from water
Explanation: Boric acid is a Lewis acid: B(OH)₃ + H₂O → [B(OH)₄]⁻ + H⁺, so it produces H⁺ by accepting OH⁻ rather than donating a proton.
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.