Dielectric Constant and Dipole Moment

Dielectric constant

Understanding the concept of dielectric constant is necessary for discussing dipoles and solvation. Two parallel conducting plates (condensers) are separated from each other by a medium through a distance (r). Two parallel conducting plates (condensers) are separated from each other by a medium through a distance (r). A charge on an electrode is q, and a charge on another electrode is -q. However, the potential difference between the electrodes is V.

Parallel plate condenser dielectric constant

A charge is encoded on the electrodes with a capacitance, while a potential difference between the electrodes is encoded with a voltage. The coulombage measure is the amount of electricity stored on the plates with a given voltage.

C = q/V

In the condenser, the capacitance is dependent on both the separation medium and the thickness of the plate. The capacitance is C0 when the spaces between the plates are filled with a vacuum. Water molecules in the space will also increase the capacitance. Since water molecules' negative ends will be located closest to the positive condenser plate and their positive ends will be closest to the negative condenser plate, the capacitance will increase with the presence of water. Having the plates aligned increases the ability of electrons to move between the plates, resulting in additional movement of charge.

The capacitance Cx in a condenser filled with a particular material is determined by dividing it by C0, where ε is the dielectric constant. Dielectric constants represent a solvent's ability to sustain a charge separation during its dissolution.

There are different dielectric constants for different liquids at 25 C - table 1

Solvent	Dielectric constant
Water solvent	78.5
Glycerin solvent	42.5
Menthol solvent	32.6
Ethanol solvent	25
Diethyl ether solvent	4.34
Olive oil solvent	3.1
Benzene solvent	2.28

In contrast, the sodium and chloride ions are separated from glycerine and water 78.5/42.5 times more easily than respectively, thus NaCl is more soluble in water than in glycerine. The condenser capacitance of polar liquids like water and methanol will increase if permanent dipoles are aligned within them, as the alignment of permanent dipoles within these liquids produces an appreciable dielectric constant. Due to their much lower dielectric constant, non-polar liquids like benzene and ether produce less polarization and have much smaller effects on capacitance.

Dipole moment

Dipole moments can be found in any system in which charges are separated from one another. This means that covalent bonds, as well as ionic bonds, can result. The dipole moment occurs when chemically bonded atoms have different electronegativity. It is the polarity of the bond between two atoms in a molecule that determines bond dipole moments. Understanding the concept of electric dipole moment is crucial to understanding it because it measures how positive and negative charges are separated in a system.

The symbols 𝛿+ and 𝛿–indicate that the two electric charges that occur in a molecule are the same magnitude, but opposite in sign. A significant distance is between them, which is typically indicated by a letter 'd'.

Important points

• Dipole moments of individual bonds in polyatomic molecules are called bond dipole moments, and these dipole moments differ from the dipole moments of the entire molecule.
• A vector quantity has both magnitudes and directions, so it can be described as a vector.
• Veterinary drug dipoles can also be zero as their oppositely acting interactions can cancel each other out as a vector quantity.
• Veterinary drug dipoles can also be zero as their oppositely acting interactions can cancel each other out as a vector quantity.
• In chemistry, dipole moments are denoted by an arrow symbol with a slight variation. In the positive center, a cross appears, and in the negative center, an arrowhead appears. Arrowheads indicate electron density shifts in molecules.
• Dipole moments of polyatomic molecules represent the vector sum of the dipole moments of all the bonds in the molecule.

Dipole moment formula

If the distance between the centers of the two charges is half the magnitude of a dipole moment, you get half the magnitude of the dipole moment. 'µ' is the Greek letter used to represent it.

Specifically,

Dipole Moment (µ) = Charge (Q) × distance of separation (r)

A Debye unit is represented by 'D'. 1 D = 3.33564 × 10-30 C.m.

Where C = coulomb and m = metre.

In the illustration below, you can see how you can calculate the bond dipole moment in a chemical bond between two atoms with different electronegativity:

μ = 𝛿.d

Where,
Dipole moments of bonds are represented by µ,
The partial charges (𝛿),+ and 𝛿–are denoted by the magnitude of these signs
A distance exists between 𝛿+ and 𝛿–.

In addition to its vector quantity, the direction parallel to the bond axis is a principal vector quantity in the bond dipole moment (µ). Chemistry indicates the presence of dipole moments through the use of arrows beginning with the positive charge and ending with the negative charge.

In atoms with varying electronegativities, electrons tend to move away from their original positions because of their attraction to the atom with a more electronegative charge. The bond dipole moment enables us to see the movement of the electrons.

Get subject wise printable pdf documentsView Here

Share

Tweet

Share

Share