Tag: structure of some compounds

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Questions Related to structure of some compounds

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

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

Which reaction cannot give anhydrous $AlCl _3$ ?

  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 $Cl _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
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.
$Al\left( { H } _{ 2 }O \right) _{ 6 }{ Cl } _{ 3 }\rightarrow { Al\left( OH \right)  } _{ 3 }+3HCl+{ 3H } _{ 2 }O$

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

Which of the following statements is correct ?

  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.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Both BCl3 and AlCl3 are Lewis acids because they have an incomplete octet. BCl3 is a stronger Lewis acid than AlCl3 because the boron atom is smaller, making the vacant p-orbital more accessible for electron donation.

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

Anhydrous $AlCl _3$ is prepared by :

  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.
Reveal answer Fill a bubble to check yourself
B Correct answer
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 $750 ^0C$
$2Al + 6HCl \; \longrightarrow \; 2Al{Cl} _3 + 3{H} _2$
Multiple choice chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

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

  1. $Al(OH) _3+HCl$
  2. $[Al(H _2O) _6]^{3+}+3Cl^-$
  3. $AlCl _3.2H _2O$
  4. $Al _2O _3+HCl$
Reveal answer Fill a bubble to check yourself
B Correct answer
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 $[Al({H _2O)} _6]^{+3} +3{Cl}^{-}$.

$Al{Cl} _3 + 6H _2O \; \longrightarrow \; [Al({H _2O)} _6]^{+3} + 3{Cl}^{-}$
Multiple choice chemistry p- block elements-i study of aluminium chloride study of aluminium structure of some compounds

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 :

  1. $Al^{3+} +2Cl$
  2. $Al _2O _3+6HCl$
  3. $[Al(OH) _6]^3+3HCl$
  4. $[Al(H _2O) _6]^{3+}+3Cl$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Similar to question 430733, the dissolution of AlCl3 in water results in the formation of the octahedral hexaaquaaluminum(III) complex and chloride ions.

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

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

  1. Solid $AlCl _3$
  2. Dimer $Al _2Cl _6$
  3. $Al(OH) _3$
  4. $Al _2O _3$
Reveal answer Fill a bubble to check yourself
D Correct answer
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.