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Questions Related to chemistry

$AlX _3$ (X = Cl, Br) exists as dimer and retains dimer formula in non-polar solvents like ether and benzene.

chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

  1. True

  2. False

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Correct Option: A
Explanation:

In the liquid state aluminium trichloride exists as the dimer with tetracoordinate aluminium. This change in structure is related to the lower density of liquid phase. These dimers are also found in the vapor phase. At higher temperature dimers dissociate into trigonal planar. The melt conducts electricity poorly.

Which reaction cannot give anhydrous $AlCl _3$ ?

chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

  1. Heating of $AlCl _3.\, 6H _2O$

  2. Passing dry HCl over heated aluminium powder

  3. Passing dry $Cl _2$ over heated aluminium powder

  4. Heating a mixture of alumina and coke in a current of dry $Cl _2$

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Correct Option: A
Explanation:

Aluminium chloride reacts with water to form  hexahydrate. The anhydrous phase cannot be regained on heating as HCl is lost leaving aluminium hydroxide or alumina.
$Al\left( { H } _{ 2 }O \right) _{ 6 }{ Cl } _{ 3 }\rightarrow { Al\left( OH \right)  } _{ 3 }+3HCl+{ 3H } _{ 2 }O$

Which of the following statements is correct ?

chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

  1. $BCl _{3}$ and $AlCl _{3}$ are both Lewis acids and $BCl _{3}$ is stronger than $AlCl _{3}$

  2. $BCl _{3}$ and $AlCl _{3}$ both Lewis acids and $AlCl _{3}$ is stronger than $BCl _{3}$

  3. Both $BCl _{3}$ and $AlCl _{3}$ are both equally strong Lewis acids.

  4. Both $BCl _{3}$ and $AlCl _{3}$ are not Lewis acids.

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Correct Option: A

$AlCl _3$ is:

chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

  1. anhydrous and covalent

  2. anhydrous and ionic

  3. covalent and basic

  4. coordinate and acidic

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Correct Option: A

Alumina is:

chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

  1. acidic

  2. basic

  3. amphoteric

  4. none of the above

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Correct Option: C
Explanation:

Allumina is $Al _2O _3$ reacts as both acid and base in chemical reactions. So it is called amphoteric oxide.
Hence option $C$ is correct.

Anhydrous $AlCl _3$ is prepared by :

chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

  1. reaction of HCl and Al metal

  2. reaction of dry HCl and heated Al metal

  3. passing $Cl _2$ gas over heated Al metal

  4. reaction of $Al _2O _3$ with dil HCl.

Show answer
Correct Option: B
Explanation:
Answer:- (B) reaction of dry $HCl$ and heated $Al$ metal.
Aluminium chloride is manufactured on a large scale by the exothermic reaction of heated aluminium metal with dry hydrogen chloride at temperatures between $650$ to $750 ^0C$
$2Al + 6HCl \; \longrightarrow \; 2Al{Cl} _3 + 3{H} _2$

$AlCl _3$ achieves stability by forming a dimer. In trivalent state the compound is hydrolysed in water. $AlCl _3$ in acidified aqueous solution forms :

chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

  1. $Al(OH) _3+HCl$

  2. $[Al(H _2O) _6]^{3+}+3Cl^-$

  3. $AlCl _3.2H _2O$

  4. $Al _2O _3+HCl$

Show answer
Correct Option: B
Explanation:
Answer:- (B) $[Al({H _2O)} _6]^{+3} +3{Cl}^{-}$

The electron deficiency of Aluminium atom in $Al{Cl} _3$ is compensated by formation of co-ordinate bond between lone pair of Chlorine atom of another $Al{Cl} _3$ molecule and the empty unhybridised p orbital of Aluminium atom, thus forms dimer and in acidified aqueous solution forms $[Al({H _2O)} _6]^{+3} +3{Cl}^{-}$.

$Al{Cl} _3 + 6H _2O \; \longrightarrow \; [Al({H _2O)} _6]^{+3} + 3{Cl}^{-}$

Aluminium chloride exists as dime , $Al _2Cl _6$ in solid state as well as in solution of non-polar solvents like benzene.When dissolved in water, it gives :

chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

  1. $Al^{3+} +2Cl$

  2. $Al _2O _3+6HCl$

  3. $[Al(OH) _6]^3+3HCl$

  4. $[Al(H _2O) _6]^{3+}+3Cl$

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Correct Option: D

Which of the following will be formed, if we heat an aqueous solution of $AlCl _3$ to dryness?

chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

  1. Solid $AlCl _3$

  2. Dimer $Al _2Cl _6$

  3. $Al(OH) _3$

  4. $Al _2O _3$

Show answer
Correct Option: D
Explanation:

We knoe $AlCl _3$ exists as a dimer $Al _2Cl _6$

The reactions involved are given by,
$Al _2Cl _6 .6H _2O \rightarrow Al _2O _3+3H _2O+6HCl$
So,option D is correct answer.

Anhydrous $AlCl _3$ fumes in air. What is the reason for it?

chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

  1. It is hygroscopic in nature

  2. It gives out chlorine when exposed to air.

  3. It is hydrolysed in moist air giving out fumes of $HCl$.

  4. It loses water when exposed to moist air.

Show answer
Correct Option: C
Explanation:
White fumes are due to the presence of $HCl$ gas.

Anhydrous aluminium chloride is hydrolysed partially with the moisture in the atmosphere to give $HCl$ gas. 

This HCl combines with the moisture in the air and appears white in colour.

$Al{Cl} _3 + 3H _2O \; \longrightarrow \; Al{(OH)} _3 + 3HCl \text{(white fumes)}$

Hence, the correct answer is option $\text{C}$.