Aluminium Chloride Questions

Aluminium chloride is also known as aluminium trichloride or aluminium (III) chloride. When aluminium and chlorine react, the compound is formed. AlCl3 is the chemical formula for it. Hans Christian Oersted, a Danish physicist and chemist, discovered aluminium chloride for the first time in 1825. This chemical compound is one of the oldest chemicals used, particularly in organic chemistry.

Definition: Aluminium chloride, also known as aluminium trichloride, is a term used to describe compounds with the formula AlCl3.

Aluminium Chloride Chemistry Questions with Solutions

Q-1: Which of the following is produced by using aluminium chloride in electrophilic substitution reactions?

a) Electron

b) Electrophile

c) Nucleophile

d) Arenium Ion

Answer: b) Electrophile

Explanation: Aluminium chloride in electrophilic substitution reactions is used to generate electrophiles.

Q-2: 3AlCl3 represents _______.

a) 3 atoms of AlCl3

b) 3 molecules of AlCl3

c) 3 atoms of Al

d) 3 moles of Cl

Answer: b) 3 molecules of AlCl3

Explanation: 3AlCl3 is three molecules or three moles of aluminium chloride, which contains three molecules or three moles of aluminium and nine molecules or nine moles of chlorine. We can’t say three atoms of aluminium chloride because it’s a compound made up of different atoms.

Q-3: Is AlCl3 a homonuclear or heteronuclear compound?

Answer: A molecule can be homonuclear, which means it is made up of atoms from only one chemical element, or it can be heteronuclear, which means it is made up of atoms from more than one chemical element. Since AlCl3 is made up of Aluminium and Chlorine atoms, it’s a heteronuclear compound.

Q-4: How does AlCl3 overcome its electron deficiency?

Answer: AlCl3 overcomes its deficiency by forming a dimer, as dimerisation results in the attainment of an octet of electrons in the valence shell of an aluminium atom.

Q-5: What happens when the aluminium chloride dimer is dissolved in water?

Answer: When the halides are dissolved in water, the high enthalpy of hydration is sufficient to break the covalent dimer into [M.6H2O]3+ and 3X ions.

Q-6: Which of the following holes is occupied by Al3+ at low temperatures?

a) Tetrahedral

b) Octahedral

b) Both the above

d) Cubical

Answer: b) Octahedral

Explanation: At low temperatures, AlCl3 exists as a closed-packed lattice of Cl with Al3+ occupying octahedral holes.

Q-7: What are the various uses of Aluminium Chloride?


  • It is used in the production of lubricants, rubber, paints, wood preservatives, and petrochemicals such as ethylbenzene.
  • Aluminium chloride is used in the polymerisation and isomerisation of light-weighted hydrocarbons, such as the synthesis of ethylbenzene.
  • Many chemical reactions use aluminium chloride as a catalyst. It is used to make anthraquinone from benzene and phosgene.
  • To create arene metal complexes, aluminium chloride is combined with aluminium and arene.

Q-8: Can aluminium chloride undergo back bonding?

Answer:.No, aluminium chloride cannot undergo back bonding because a second period element is required for back bonding to occur. Because both aluminium and chlorine are third period elements, back bonding cannot occur in this molecule.

Q-9: Aluminium Chloride is hygroscopic in nature because it can ______.

a) React with water

b) Absorb moisture

c) Sublime easily

d) Absorb gases

Answer: b) Absorb moisture

Explanation: Hygroscopic refers to a matter’s ability to absorb water from the surrounding environment. Aluminium chloride is deemed to be hygroscopic, where it can absorb moisture from the air.

Q-10: Is aluminium chloride dangerous to human beings?

Answer: Aluminium chloride is a highly corrosive and toxic substance. If inhaled or touched, it can cause severe damage to the eyes, skin, and respiratory systems.

Q-11: How many chlorine atoms are there in one mole of aluminium chloride?

Answer: One mole of aluminium chloride contains Avogadro’s number (6.022×1023) of atoms.

In AlCl3, there are three chlorine atoms. Thus, one mole of aluminium chloride will contain 3 × 6.022×1023 atoms = 18.066 ×1023 atoms of chlorine.

Q-12: Which gas is formed when aluminium chloride hexahydrate is heated?

a) HCl

b) H2

c) Cl2

c) O2

Answer: a) HCl

Explanation: When aluminium chloride hexahydrate is heated, the following reaction takes place:

2AlCl3.6H2O + Heat → Al2O3 + 6HCl↑ + 9H2O

We can clearly see that HCl gas is being evolved out.

Q-13: How does aluminium chloride exist in the gas phase?

a) Polymer

b) Dimer

c) Tetramer

d) None of the above

Answer: b) Dimer

Explanation: Aluminium chloride exists as a dimer in the gas phase. Al2Cl6 is the dimer of aluminium chloride in the gas phase.

Q-14: Is AlCl3 soluble in water?

Answer: AlCl3 is a colourless crystalline solid which is soluble in water.

Q-15: Which of the following is an important Ziegler Natta catalyst?

a) Solution of AlEt3+ TiCl4

b) Solution of AlCl3+ TiCl3

c) Solution of Al2Cl6+ TiCl4

d) Solution of Al2(CH3)6+ TiCl4

Answer: a) Solution of AlEt3+ TiCl4

Explanation: Ziegler Natta catalyst is used for the polymerisation of ethene to form polythene and a solution of AlEt3+ TiCl4 in a hydrocarbon solvent is an important Ziegler Natta catalyst.

Practice Questions on Aluminium Chloride

Q-1: Aluminium chloride is a _________.

a) Bronsted Acid

b) Bronsted Base

c) Lewis Acid

d) Lewis Base

Q-2: The reaction of benzene with ethanoyl chloride produces electrophile in the presence of Lewis acids, AlCl3. Show the mechanism for this.

Q-3: What are the various physical properties of Aluminium Chloride?

Q-4: What is the nature of the aqueous solution of Aluminium chloride?

Q-5: Which of the following contains the 3c-4e bond?

a) Al2(CH3)6

b) Al2Cl6

c) AlCl3

d) All of the above

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