Question

Among the following, van der waals force are maximum in:
A. HBr
B. LiBr
C. LiCl
D. AgBr

Answer 1

Hint: To give the answer of this question, we use the basic theory of bonding .First of all we see the definition of van der Waals force. This force is applied to all gases. It depends on the relative orientation of the molecules. This force is independent of temperature except dipole-dipole interaction.

Complete step-by-step answer:
The force between polar as well as non polar molecules is called van der waals force.
This force acts between atoms, molecules and surface .This force is discovered by Dutch scientist Johannes Diderik van der Waals. This is distance dependent force. it can attract and repel atoms.
There are three types of van der waals forces.
1. London force
2. Dipole- Dipole force
3. Hydrogen force
HBr is a covalent bond. What is covalent bond?
A covalent bond is a chemical bond formed by equal sharing of electrons.
Example- HCl, $CO_2$,
LiBr, LiCl, AgBr, are ionic bonds.
What is an ionic bond?
The bond which is formed between cation and anion is called ionic bond.
In LiBr; Li+ cation size is very small and the anion size Br- is very large.
In LiCl; the size of Li+ cation is very small and the size of Cl- anion is large.
In AgBr; the size of Ag+ cation is large and size of Br- is also large.
The distance between Li+ ion and Br- ion is greater than all of the above.
So, LiBr has the greatest van der waals force.

Note-In the periodic table go through top to bottom the atomic size and atomic radius increase. Van der Wal force is actually an interaction which is due to induced charges.Therefore, Van der Waals forces are weaker than normal covalent and ionic bonds.