Review Explain the intermolecular forces of the London dispersion, Dipole-Dipole

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Explain the intermolecular forces of the London dispersion, Dipole-Dipole and Hydrogen bonding

Also explain how to determine whether a compound or molecule has the highest or lowest vapor pressure, melting point, boiling point, freezing point, viscosity, the heat of vaporization, and enthalpy of fusion? proportionality laws

Also if you are comparing compounds which have the same intermolecular forces, how can you determine which has the lowest of greatest characteristics stated above.

given an example,

Explanation / Answer

London dispersion force: The distribution of electrons in an atom or molecule flactuates in time. Sometimes the electrons can concentrate themselves unevenly creating an instantaneous dipole. This instantaneous dipole thus created can have influence on surrounding atoms or molecules such that they redistribute their electron density which is referred to as an induced dipole. These instantaneous and induced dipoles will have their opposite poles facing each other. This results in the temporary alignment of atoms or molecules.

London dispersion force becomes stronger with the increase of the size of atoms or molecules. This is why I2 is solid, Br2 is liquid, while Cl2 and F2 are gases at room temperature.

Dipole-Dipole interaction: This happens when the opposite poles of two polar molecules interact with each other. For example, molecules of hydrogen chloride gas. The H-end gets partial positive charge and Cl-end gets partial negative charge as the electronegativity of Cl> the electronegativity of H. In dipole -dipole interaction the H-end of one H-Cl molecule interacts with the Cl end of another H-Cl. This is predominantly an attractive interaction.

H-bonding: This is the interaction of partially positive H-atom (attached to a highly electronegative atom) of one moiety with that of the lone pair of an electronegative atom. This can be intermolecular as well as intramolecular. E.g. H-F---H-F---H-F...

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Lower vapor pressure, higher melting point, higher boiling point, higher freezing point, higher viscosity, higher heat of vaporization, and higher enthalpy of fusion are the characterestics of molecule having strong intermolecular forces.

For example : Compare H2O and H2S. H2O forms stronger hydrogen bonds between themselves than H2S. Thus H2O will show above characterestics in comparison with H2S.

About your hypothetical question: It is not possible to have two different compunds having exactly same intermolecular forces.

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