JEE Questions for Chemistry Class 11 P Block Elements Quiz 13 - MCQExams.com

At.No.of M is less than 21.

Therefore, M belongs to representative elements. As MX₃ has zero dipole moment, it has a regular geometry i.e. trigonal planar which is obtained by sp² – hybridization.

BF₃ is a colourless gas whereas BCl₃ and BBr₃ are colourless fuming liquids at room temperature.

FeSO₄.Al₂(SO₄)₃.24H₂O is not a true alum because in place of Fe²⁺ ion here should be monovalent ion in true alum

Al₂(SO₄)₃ makes the clothes fire proof.

Al liberates H₂ from both acids and alkalies. For example,

2Al + 6HCl → 2Al₂Cl₃ + 3H₂; also refer to Ans, No.13

4LiH + AlCl₃ → LiAlH₄ + 3LiCl

Al₂O₃ is not used as a constitutent of baking powder.

Al is more electropositive than Fe and therefore, it reduces Fe₂O₃ to Fe . The heat produced in this reaction is so large that the metal is produced in the molten state which can be used for welding purposes.

On heating AlCl₃.6H₂O, hydrolysis takes places giving Al(OH)₃ and hydrogen chloride.Al(OH)₃ then loses H₂O to form Al₂O₃.

Thermite process involves the use of Al metal and Fe₂O₃. For further details refer to ans. No 22 above

Al₂O₃ has high lattice energy and low heat of hydration.It is therefore, insoluble in water.

Anhydrous AlCl₃ is a covalent compound which sublimes on heating.

Al₂O₃ is most amphoteric in nature. It reacts with acids as well as alkalies.

Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O

Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O

A mixture of one part of powdered Al and three parts of Fe₂O₃ is called thermite.

Al reduces Fe₂O₃ or Cr₂O₃ to respective metals and acts as a reducing agent

Fe₂O₃ + 2Al → Al₂O₃ + 2Fe

In Baeyer’s process for purification of red bauxite, ferrous is oxidized to ferric state and then bauxite is digested with NaOH to dissolve aluminium as sod. meta aluminate whereas iron is removed as Fe(OH)₃ ppt.

Al is more electropositive and has greater affinity for oxygen than iron. This fact is made use of in aluminothermy.

For example, Cr₂O₃ + 2Al → Al₂O₃ + 2Cr involves Al₂O₃ formation and large amount of heat is evolved.

As Ga remains liquid over a wide range of temperature (303 k to 2510 K) It is used in high temperature thermometry.

In the Hoope’s process for refining of Al , the fused materials form three different layers because of their different densities.

Oxidation number of metal M when M³⁺ loses three electrons will be (M³⁺ – 3e^- → M⁶⁺ ) +6.

Electrolytic reduction of Al₂O₃ to Al by Hall Heroult process is carried out in the presence of cryolite which forms a melt with lower melting temperature.

2Al + 6HCl (dil) → 2AlCl₃ + 3H₂

2Al + 2NaOH + 6H₂O → 2Na[Al(OH)₄] + 3H₂

Pseudo alum has the general formula M^IISO₄, M₂^III(SO₄)₃ .24H₂O.

Therefore FeSO₄. Al₂(SO₄)₃. 24 H₂O is a pseudo alum.

Cryolite mineral is Na₃AlF₆

Mixture of Al powder and Al(NO₃)₃ known as ‘Ammonal’ is used in bombs.

Ruby is a gemstone containing Al₂O₃ and traces of Cr³⁺ metal ion as impurity. It attains a red colour. Similarly. Sapphire is Al₂O₃ + traces of Fe²⁺, Fe³⁺ and Ti⁴⁺ ions as impurities. It acquires a blue colour.

As we move from F to Br down the group, the size of p-orbital of halogen increases and the extent of overlap between 2 – p – orbital of B and p – orbital of the halogen and tendency of back donation of electrons from filled p-orbital of halogen to empty p – orbital of B atom decrease. Consequently the electron deficiency of the boron atom increases from BF₃ through BCl₃ to BBr₃ and hence acidity increases in the same order.