topic 3

Question 1

Intermolecular forces

Answer 1

-these are forces of attraction or repulsions b/w molecules. they influence physical properties like BP, MP & solubility

Question 2

Hydrogen bonding

Answer 2

-Strongest intermolecular force that occurs when a hydrogen atom is bonded to a highly electronegative atom (such as oxygen, nitrogen,
or fluorine) . Contributes highly to properties of molecules like water

Question 3

Criteria of H-bond formation

Answer 3

1.When H is bonded to a highly EN atom like N, O, or F. They pull electron density from H leaving it partially positive like in water
2.The EN elments must havea lone pair of electrons available. This pair will form a partial - charge on the atom
3.H must be close enough to the EN atom
4.Angle between them should be linear or nearly, optimal angle maximizes electrostatic attraction b/w H & the EN atom

Question 4

Hydrogen bonding in organic compounds

Answer 4

Hydrogen bonding is responsible for many important properties of substances, such as the high
boiling points of water and ammonia.

It also plays a crucial role in the structures and properties of
biological molecules, such as DNA and proteins

Alcohols can form H-bond with each other ,
Ethers cannot , ethers can forb H-bond only with water

Question 5

Van der Waals forces: dipole-dipole and London forces.

Answer 5

Van der Waals forces are weak intermolecular forces that exist between molecules. They can be divided into two main types: dipole-dipole interactions and London dispersion forces.

1.Dipole-dipople: b/ polar molecules, where 1 has a permanent dipole moment due to the EN diif between atoms/ nature: positive end of polar attracts negative end of othe rpolar leading to weak electrostaric attraction/ stronger than London dispersion forces but weaker than H-bon & ionic bonds e.g HCl; H is partially positive and attracted to partially - Cl
2.London dispersion forces: weakest type/ nature: from temporary fluctuations in electron distribution aroound atoms/molecules. the temporary dipoles induce similar temporary dioples in neighboring molecules hence weak intermolecular forces/ forces increases with size of molecule & no of electrons/ e.g: CH4