Question:

Aluminum reacts with dilute HCL and liberates a gas 'A' and with aqueous alkali liberates a gas 'B'. A and B respectively are

Updated On: Apr 11, 2025
  • Cl2, O2

  • O2,O2

  • Cl2.H2

  • H2,H2

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The Correct Option is D

Solution and Explanation

To solve the problem, we need to identify the gases evolved when aluminium reacts with dilute hydrochloric acid and with aqueous alkali.

1. Reaction with Dilute HCl:
Aluminium is a reactive metal and reacts with dilute hydrochloric acid to liberate hydrogen gas ($H_2$):
$2Al + 6HCl \rightarrow 2AlCl_3 + 3H_2 \uparrow$
So, gas ‘A’ is Hydrogen ($H_2$).

2. Reaction with Aqueous Alkali:
Aluminium is amphoteric — it reacts with bases like NaOH to form sodium aluminate and hydrogen gas:
$2Al + 2NaOH + 6H_2O \rightarrow 2Na[Al(OH)_4] + 3H_2 \uparrow$
So, gas ‘B’ is also Hydrogen ($H_2$).

Final Answer:
The gases A and B liberated in the two reactions are H2, H2.

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Concepts Used:

Chemical Bonding and Molecular Structure

Such a group of atoms is called a molecule. Obviously, there must be some force that holds these constituent atoms together in the molecules. The attractive force which holds various constituents (atoms, ions, etc.) together in different chemical species is called a chemical bond.

Types of Chemical Bonds:

There are 4 types of chemical bonds which are formed by atoms or molecules to yield compounds. 

  • Ionic Bonds - Ionic bonding is a type of chemical bonding which involves a transfer of electrons from one atom or molecule to another.
  • Covalent Bonds - Compounds that contain carbon commonly exhibit this type of chemical bonding. 
  • Hydrogen Bonds -  It is a type of polar covalent bonding between oxygen and hydrogen wherein the hydrogen develops a partial positive charge
  • Polar Bonds - In Polar Covalent chemical bonding, electrons are shared unequally since the more electronegative atom pulls the electron pair closer to itself and away from the less electronegative atom.

Factors Affecting Bond Enthalpy in Chemical Bonding:

  • Size of the Atom
  • Multiplicity of Bonds
  • Number of Lone Pair of Electrons Present
  • Bond Angle