Group 13 2 Flashcards
(38 cards)
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Why is boron unreactive in its crystalline form?
Because its structure makes it chemically inert.
How does aluminium resist corrosion?
It forms a very thin oxide layer that protects it from further attack.
What happens when amorphous boron and aluminium metal are heated in air?
They form B₂O₃ and Al₂O₃, respectively.
What do boron and aluminium form when heated with dinitrogen at high temperatures?
They form nitrides.
How does the nature of oxides change down Group 13?
Boron oxide is acidic, aluminium and gallium oxides are amphoteric, and indium and thallium oxides are basic.
What happens when boron trioxide reacts with metallic oxides?
It forms metal borates.
Does boron react with acids and alkalies at moderate temperatures?
No, boron does not react with acids and alkalies even at moderate temperatures.
How does aluminium behave with acids and alkalies?
Aluminium dissolves in mineral acids and aqueous alkalies, showing amphoteric character.
What happens when aluminium reacts with dilute HCl?
It liberates dihydrogen gas. Equation: 2Al(s) + 6HCl (aq) → 2Al³⁺ (aq) + 6Cl⁻ (aq) + 3H₂ (g)
What happens when aluminium is treated with concentrated nitric acid?
It becomes passive due to the formation of a protective oxide layer.
How does aluminium react with aqueous alkali?
It liberates dihydrogen gas and forms sodium tetrahydroxoaluminate(III). Equation: 2Al (s) + 2NaOH(aq) + 6H₂O(l) → 2Na⁺ [Al(OH)₄]⁻ (aq) + 3H₂(g)
How do Group 13 elements react with halogens?
They form trihalides, except for TlI₃.
What is the general equation for the reaction of Group 13 elements with halogens?
2E(s) + 3X₂(g) → 2EX₃(s) (X = F, Cl, Br, I)
What happens when the trichlorides, bromides, and iodides of Group 13 elements are added to water?
They are hydrolyzed because they are covalent in nature.
What species exist in aqueous medium for Group 13 elements (except boron)?
Tetrahedral [M(OH)₄]⁻ and octahedral [M(H₂O)₆]³⁺.
Why are monomeric trihalides of Group 13 strong Lewis acids?
Because they are electron-deficient.
How does boron trifluoride (BF₃) react with ammonia (NH₃)?
It forms a Lewis acid-base complex to complete boron’s octet. Equation: BF₃ + NH₃ → F₃B - NH₃
Why is boron’s maximum covalence limited to 4?
Because boron lacks d orbitals.
Why can aluminium and other Group 13 elements have a covalence greater than 4?
Because they have available d orbitals.
Why do some metal halides like AlCl₃ form dimers?
They dimerize through halogen bridging (e.g., Al₂Cl₆) to complete the metal’s octet.
Why is boron unable to form the BF₆³⁻ ion?
Due to the non-availability of d orbitals, boron cannot expand its octet beyond four bonds.
What are the physical properties of boron?
Boron is extremely hard, refractory, has a high melting point, low density, and very low electrical conductivity.
Where are boron fibers used?
Boron fibers are used in making bullet-proof vests and light composite materials for aircraft.
