Dipole and dipole moment; molecular polarity
Dipole: A dipole as the name suggests, two opposite spins.
The dipole is defined as a pair of opposite charges separated by a distance “x”. A dipole consists of two opposite charges which have an attractive force acting amongst them, yet separated by some distance.
When a dipole is acted upon by an angular force tangentially, a torque is generated in the dipole and an angular displacement of the dipole from its mean position. This torque generated in the dipole due to this tangential force is termed as the DIPOLE MOMENT.
The dipole moment is also defined as the angular displacement which a dipole would experience when an external force is applied.
In terms of electrical charges, the dipole moment is defined as the product of the magnitude of charge and distance separating them.
Characteristics of dipole moment:
- It is a vector quantity.
- Varies with the magnitude of the charge.
- Independent of the nature of the charge.
- Gives the angular displacement when the dipole is acted upon by an external force.
Dipole Moment in Terms of Chemistry:
Various molecules possess a polar nature; that is, their constituents are charged particles(ions) which combine to form bonds, maintaining the electrical neutrality. For example WATER
Water is a mixture formed when 2 moles of hydrogen combine with 1 mole of oxygen, under certain temperature-pressure conditions. When observed microscope it was found that the bonding between Hydrogen and oxygen is like this:
Where H has a positive charge over it and OH has a negative charge. Hence the water molecule is considered to be a dipole where H and OH are separated by some distance. This distance in chemical terms is called as the bond-length.
Now the dipole moment can also be calculated using the formula: Where q is the magnitude of charge and d is the distance of separation.
The unit for the quantity is coulomb meter. (Cm) calculation of dipole moment gives the polarity for the molecule taken under consideration.
A molecule is said to be polar when equal charges of opposite spins combine to form bonds and when diluted the constituents dissociate into their ionic characters.
The polar molecules will be miscible in polar solvents only. This is the reason why oil never mixes with water and forms layers. Natural oil is non-polar in nature hence doesn’t dissociate in water because ionization of non-polar compound is not possible.
Polar molecules show following characteristics:
- They have low dissociation enthalpy.
- High electrical conductivity.
- Lower molar conductivity.
- High dilution capability.
- High ionization capacity.
Water A Polar Molecule:
Water is considered as the universal polar molecule because of its universally neutral nature, the presence of a hydrogen bond in it, the difference in electronegativity between "H" and "O" atom, high dissociation intensity, greater ionisation capability and high dissolution power. The pH of water shall be 7.
Uses of Water:
Water has various application in domestic as well as commercial sectors. Some of them are listed below:
- In commercial sectors like pharmaceuticals and fertilisers, water is the key medium of bacteria culture and dissolving the mixture as well.
- In domestic sector water is used for washing, cleaning, drinking, cooking and much more.
Hence in the above content, the concept of dipole moment along with suitable examples have been mentioned. to understand the concept of dipole moment and polarity of molecules, an example of water has been mentioned. hope the above content was fruitful.