INTERMOLECULAR FORCES Flashcards
What is a London dispersion force (LDF)?
The electrostatic attraction between a temporary dipole and a temporary induced dipole.
What is a dipole?
A separation of charge.
What are the weakest intermolecular bond?
London dispersion forces.
How do London dispersion forces arise?
LDFs are caused by an uneven distribution of electrons within an atom. This causes and electron wobble, then a temporary dipole. Any neighbouring atoms end up having a temporary induced dipole. The electrostatic attraction between these two atoms is LDF.
What is the only type of bonding present in noble gases?
London dispersion forces.
What effects the strength of LDFs in noble gases?
The key factor affecting the strength of the LDF is the size of the atom. The larger an atom is the more likely it is that the clouds will be able to ‘wobble’ and set up a temporary dipole. The larger the dipole the stronger LDF.
What is hydrogen bonding?
Hydrogen bonding is the name given to an intermolecular force which is a type of permanent dipole-Permanent dipole attraction.
What is needed for hydrogen bonding to occur?
The hydrogen atom involved needs to be the positive end of a strong dipole and needs to have a small, highly electronegative atom on a neighbouring atom.
What three elements can satisfy the requirements of hydrogen bonding?
Fluorine
Nitrogen
Oxygen
What happens when water freezes?
As water freezes, the intermolecular hydrogen bonding spreads out the water molecules into a stronger ‘open’ structure with larger spaces. This makes ice less dense and able to float on water.
What is viscosity?
Viscosity is the measure of how easily it flows (how thick or syrupy a liquid is). The stronger the intermolecular forces are between molecules in a liquid. The more viscous the liquid.
What happens to a mixture of polar and non-polar substance.
No dissolving occurs, opposites do not dissolves. Like dissolves Like.
What is miscibility?
When two liquids mix thoroughly with no visible boundary between them, they are said to be miscible.
When does miscibility arise?
Miscibility arises when the intermolecular attractions between two types of substances are fairly similar, they are then able to mix easily.
